From 04646f334cad09d784e2b68aa4b7639cd7c10b18 Mon Sep 17 00:00:00 2001
From: Benjy Weinberger <benjyw@gmail.com>
Date: Wed, 29 Jul 2020 20:35:08 -0700
Subject: [PATCH 01/21] Fix the setup-py part of the example. (#28)

Required moving the .proto files to be
below the exported target (in the filesystem
sense).

If we support setting a source root on
generated protos in the future, we can
modify this further to demo that.
---
 .gitignore                                     |   4 ++++
 helloworld/BUILD                               |   2 +-
 helloworld/config.py                           |   2 +-
 helloworld/db.sqlite3                          | Bin 0 -> 24576 bytes
 helloworld/util/BUILD                          |   4 ++--
 helloworld/util/config_loader.py               |   2 +-
 helloworld/{protos => util/proto}/BUILD        |   2 +-
 helloworld/{protos => util/proto}/config.proto |   2 +-
 8 files changed, 11 insertions(+), 7 deletions(-)
 create mode 100644 helloworld/db.sqlite3
 rename helloworld/{protos => util/proto}/BUILD (71%)
 rename helloworld/{protos => util/proto}/config.proto (87%)

diff --git a/.gitignore b/.gitignore
index f7a6370..97b1dfa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,7 @@ __pycache__/
 
 # Editors
 .idea/
+*.iml
+
+# Local databases.
+*.sqlite3
diff --git a/helloworld/BUILD b/helloworld/BUILD
index bf588a4..b4b9546 100644
--- a/helloworld/BUILD
+++ b/helloworld/BUILD
@@ -40,8 +40,8 @@ python_library(
     sources = ["config.py"],
     dependencies = [
         ":config_file",
-        "helloworld/protos",
         "helloworld/util",
+        "helloworld/util/proto",
     ],
 )
 
diff --git a/helloworld/config.py b/helloworld/config.py
index d3cdc96..7d56799 100644
--- a/helloworld/config.py
+++ b/helloworld/config.py
@@ -1,8 +1,8 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from helloworld.protos.config_pb2 import Config
 from helloworld.util.config_loader import load_config_from_json
+from helloworld.util.proto.config_pb2 import Config
 
 
 def load_config() -> Config:
diff --git a/helloworld/db.sqlite3 b/helloworld/db.sqlite3
new file mode 100644
index 0000000000000000000000000000000000000000..093e09e0f69421aa6ad3122260f0b78985eac85e
GIT binary patch
literal 24576
zcmeI)&2rmB00;1uEZdZ6svbx+ZRxPc^)#L|jx5z54HpcU#;xPDsWXt1s#se`RF)h`
zE_8qy+%qR0fg8L655R$*`U)_^Yp`-1e^t#4y^tCHJ7Z~A`{CW+Du>-!=i!5v6EXVO
z5BgR_4RVnP0{NIyLP(Z>GW>HA&hv<LlHhk?F8-!ymK3l5u)=fG=K~^Nzwq)xX5}Lu
zMSuVVAOHafKmY;|fB*!}w1D{QY26clJS}%VZ}j=OtYR3#b0e}2UDgX2i_8HFLf?!0
zaVp_a=F`1Kz0;tb`X{XhRTE06bWL?^l{#L;dMu#r-41Q<w_5c6UUR3ucR=qo4rqP9
zv)gR*wssor&P}R@?y#rQr&iECvVt{TD@?2L%*R95H9f1(W+lpVB?_bMce09a2%~Qu
z&t~7)Us+zyH@kco%!|zE*?^hWU|_n|A#=^XZ}V%la%da2acB-b=QyE)G#Tc8yZK<h
zL7VN*8edX1q2TE)t8}-WSS?1H_DSVq9Cu4CjGEb3b8>q;CkbDe@F=}FCkZ9qYEEYT
zn@&tgn{%J`Iyt*=U(6`$>%zf!B;m2km$zofj)%<avZZ8dVFXK=Yw^_I<TVSU10kzy
zZVJz>d7Zw~3#`cTy>K$}*#mK*-IMv7<-e`V>_ybe<%M^3@ikq}<)p5|_#cODMJ#gq
zZ2FoP;<dRXzfa`f<?rQtJc0lL2tWV=5P$##AOHafKmY;|_@4=ENNJ*cP#<qLX_}^+
zeEDqYnyzhVm5oxB>iSlxvQ@fWG>q!4a#c(5;`wRulIeI(<XG-v4Xw7N*NT<uty)Rj
z7Skkur#{&-ig%2{@%IF*?>}XWTS@T>f2k#7tE?4kdaYcmRR!Ksez~PLbzxGmRMsjh
z@=KDEe<t#8^56W1009U<00Izz00bZa0SG_<0uX?}e<GkrDMLs&@RC^-Qk%kSXAj~N
z`m3*XR7vqh5>9A{@A9Ie{DR1T@e2Y3AOHafKmY;|fB*y_009U<00L)TK#`OiuXYL+
zeoiA^mGZfB^M?%P;_>-^QT~I-fAR|g1Rwwb2tWV=5P$##AOHafKmY<~UEq=^5#`4C
zq`<=Z|EeI7d~R;dAI`<&^?ycw6tDkZ$iK)x$=~q=0t6rc0SG_<0uX=z1Rwwb2tWV=
z|4QIWMk3b=eLrxlAbNI}|A;@NJCoFVX})03S+>i9X23i~>v42dlE~%U(a`4q5OXI8
zi*$P&{V>HFs=6$U0?TGiFC4IL<OlRlk+voeSNR6O<=od+#B1L5k39OtI2y12udRni
SEO7nqlZTT#-S%DHnSTJR3iD9_

literal 0
HcmV?d00001

diff --git a/helloworld/util/BUILD b/helloworld/util/BUILD
index ceed705..59f523c 100644
--- a/helloworld/util/BUILD
+++ b/helloworld/util/BUILD
@@ -7,13 +7,13 @@ python_library(
     dependencies = [
         "//:setuptools",
         "//:translate",
-        "helloworld/protos",
+        "helloworld/util/proto",
     ],
     # See https://pants.readme.io/docs/python-setup-py-goal.
     provides = setup_py(
         name='helloworld.util',
         version='0.0.1',
-        description='Greeting library utilities',
+        description='Greeting library utilities.',
     ),
 )
 
diff --git a/helloworld/util/config_loader.py b/helloworld/util/config_loader.py
index ce2f9de..74ac450 100644
--- a/helloworld/util/config_loader.py
+++ b/helloworld/util/config_loader.py
@@ -4,7 +4,7 @@
 import pkg_resources
 from google.protobuf.json_format import Parse as parse_json
 
-from helloworld.protos.config_pb2 import Config
+from helloworld.util.proto.config_pb2 import Config
 
 
 def load_config_from_json(pkg_name: str, resource_name: str) -> Config:
diff --git a/helloworld/protos/BUILD b/helloworld/util/proto/BUILD
similarity index 71%
rename from helloworld/protos/BUILD
rename to helloworld/util/proto/BUILD
index 6212f61..3ddf1d9 100644
--- a/helloworld/protos/BUILD
+++ b/helloworld/util/proto/BUILD
@@ -1,6 +1,6 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-# `name` defaults to the name of this directory, i.e., `protos`.
+# `name` defaults to the name of this directory, i.e., `proto`.
 # `sources` defaults to ["*.proto"].
 protobuf_library()
diff --git a/helloworld/protos/config.proto b/helloworld/util/proto/config.proto
similarity index 87%
rename from helloworld/protos/config.proto
rename to helloworld/util/proto/config.proto
index 8fd242c..9db68bd 100644
--- a/helloworld/protos/config.proto
+++ b/helloworld/util/proto/config.proto
@@ -3,7 +3,7 @@
 
 syntax = "proto3";
 
-package helloworld.protos;
+package helloworld.util.proto;
 
 message Config {
   repeated string languages = 1;

From 3b199d82da67dde1da16fd5926f8144c3ddeb44b Mon Sep 17 00:00:00 2001
From: Benjy Weinberger <benjyw@gmail.com>
Date: Wed, 29 Jul 2020 23:03:51 -0700
Subject: [PATCH 02/21] Delete .sqlite3 file added by accident (#29)

---
 helloworld/db.sqlite3 | Bin 24576 -> 0 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)
 delete mode 100644 helloworld/db.sqlite3

diff --git a/helloworld/db.sqlite3 b/helloworld/db.sqlite3
deleted file mode 100644
index 093e09e0f69421aa6ad3122260f0b78985eac85e..0000000000000000000000000000000000000000
GIT binary patch
literal 0
HcmV?d00001

literal 24576
zcmeI)&2rmB00;1uEZdZ6svbx+ZRxPc^)#L|jx5z54HpcU#;xPDsWXt1s#se`RF)h`
zE_8qy+%qR0fg8L655R$*`U)_^Yp`-1e^t#4y^tCHJ7Z~A`{CW+Du>-!=i!5v6EXVO
z5BgR_4RVnP0{NIyLP(Z>GW>HA&hv<LlHhk?F8-!ymK3l5u)=fG=K~^Nzwq)xX5}Lu
zMSuVVAOHafKmY;|fB*!}w1D{QY26clJS}%VZ}j=OtYR3#b0e}2UDgX2i_8HFLf?!0
zaVp_a=F`1Kz0;tb`X{XhRTE06bWL?^l{#L;dMu#r-41Q<w_5c6UUR3ucR=qo4rqP9
zv)gR*wssor&P}R@?y#rQr&iECvVt{TD@?2L%*R95H9f1(W+lpVB?_bMce09a2%~Qu
z&t~7)Us+zyH@kco%!|zE*?^hWU|_n|A#=^XZ}V%la%da2acB-b=QyE)G#Tc8yZK<h
zL7VN*8edX1q2TE)t8}-WSS?1H_DSVq9Cu4CjGEb3b8>q;CkbDe@F=}FCkZ9qYEEYT
zn@&tgn{%J`Iyt*=U(6`$>%zf!B;m2km$zofj)%<avZZ8dVFXK=Yw^_I<TVSU10kzy
zZVJz>d7Zw~3#`cTy>K$}*#mK*-IMv7<-e`V>_ybe<%M^3@ikq}<)p5|_#cODMJ#gq
zZ2FoP;<dRXzfa`f<?rQtJc0lL2tWV=5P$##AOHafKmY;|_@4=ENNJ*cP#<qLX_}^+
zeEDqYnyzhVm5oxB>iSlxvQ@fWG>q!4a#c(5;`wRulIeI(<XG-v4Xw7N*NT<uty)Rj
z7Skkur#{&-ig%2{@%IF*?>}XWTS@T>f2k#7tE?4kdaYcmRR!Ksez~PLbzxGmRMsjh
z@=KDEe<t#8^56W1009U<00Izz00bZa0SG_<0uX?}e<GkrDMLs&@RC^-Qk%kSXAj~N
z`m3*XR7vqh5>9A{@A9Ie{DR1T@e2Y3AOHafKmY;|fB*y_009U<00L)TK#`OiuXYL+
zeoiA^mGZfB^M?%P;_>-^QT~I-fAR|g1Rwwb2tWV=5P$##AOHafKmY<~UEq=^5#`4C
zq`<=Z|EeI7d~R;dAI`<&^?ycw6tDkZ$iK)x$=~q=0t6rc0SG_<0uX=z1Rwwb2tWV=
z|4QIWMk3b=eLrxlAbNI}|A;@NJCoFVX})03S+>i9X23i~>v42dlE~%U(a`4q5OXI8
zi*$P&{V>HFs=6$U0?TGiFC4IL<OlRlk+voeSNR6O<=od+#B1L5k39OtI2y12udRni
SEO7nqlZTT#-S%DHnSTJR3iD9_


From cf7721123ef6ea709653a10d8f6273b3f1c20673 Mon Sep 17 00:00:00 2001
From: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Date: Wed, 5 Aug 2020 14:50:28 -0700
Subject: [PATCH 03/21] Upgrade to 1.30.1rc0 (#31)

This fixes running `./pants setup-py --args="bdist_wheel" helloworld/util`.
---
 pants.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pants.toml b/pants.toml
index 5b4442e..a06a21e 100644
--- a/pants.toml
+++ b/pants.toml
@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 [GLOBAL]
-pants_version = "1.30.0"
+pants_version = "1.30.1rc0"
 v1 =  false  # Turn off the v1 execution engine.
 v2 = true  # Enable the v2 execution engine.
 pantsd = true  # Enable the Pants daemon for better performance.

From a91a1eb9a76b2c8116d647502bd20adb7ede3992 Mon Sep 17 00:00:00 2001
From: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Date: Tue, 11 Aug 2020 11:09:30 -0700
Subject: [PATCH 04/21] Update doc URLs to pantsbuild.org (#34)

---
 README.md             | 4 ++--
 helloworld/util/BUILD | 2 +-
 pants.ci.toml         | 2 +-
 pants.toml            | 6 +++---
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 9af10e0..70a353e 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # example-python
 An example repository to demonstrate Python support in Pants.
 
-See [pantsbuild.org](https://www.pantsbuild.org/docs) for much more detailed documentation.
+See [www.pantsbuild.org](https://www.pantsbuild.org/docs) for much more detailed documentation.
 
 # Running Pants
 
@@ -146,7 +146,7 @@ Try these out in this repo!
 
 ## Build an AWS Lambda
 
-(This example only works on Linux because it has an sdist. See https://pants.readme.io/docs/awslambda-python.)
+(This example only works on Linux because it has an sdist. See https://www.pantsbuild.org/docs/awslambda-python.)
 
 ```
 ./pants awslambda helloworld:helloworld-awslambda
diff --git a/helloworld/util/BUILD b/helloworld/util/BUILD
index 59f523c..38fe165 100644
--- a/helloworld/util/BUILD
+++ b/helloworld/util/BUILD
@@ -9,7 +9,7 @@ python_library(
         "//:translate",
         "helloworld/util/proto",
     ],
-    # See https://pants.readme.io/docs/python-setup-py-goal.
+    # See https://www.pantsbuild.org/docs/python-setup-py-goal.
     provides = setup_py(
         name='helloworld.util',
         version='0.0.1',
diff --git a/pants.ci.toml b/pants.ci.toml
index ec64bf1..636e727 100644
--- a/pants.ci.toml
+++ b/pants.ci.toml
@@ -1,4 +1,4 @@
-# See https://pants.readme.io/docs/using-pants-in-ci.
+# See https://www.pantsbuild.org/docs/using-pants-in-ci.
 
 [GLOBAL]
 pantsd = false
diff --git a/pants.toml b/pants.toml
index a06a21e..67943e8 100644
--- a/pants.toml
+++ b/pants.toml
@@ -24,15 +24,15 @@ backend_packages2.add = [
 plugins2 = []
 
 [source]
-# The Python source root is the repo root. See https://pants.readme.io/docs/source-roots.
+# The Python source root is the repo root. See https://www.pantsbuild.org/docs/source-roots.
 root_patterns = ["/"]
 
 [python-setup]
 # The default interpreter compatibility for code in this repo. Individual targets can ovverride
 #  this with the `compatibility` field. See
-#  https://pants.readme.io/docs/python-interpreter-compatibility.
+#  https://www.pantsbuild.org/docs/python-interpreter-compatibility.
 interpreter_constraints = [">=3.7"]
-# Use a lockfile. See https://pants.readme.io/docs/python-third-party-dependencies.
+# Use a lockfile. See https://www.pantsbuild.org/docs/python-third-party-dependencies.
 requirement_constraints = "constraints.txt"
 
 [protoc]

From 93810b678ff34ae72d7eb821a5425cb61a841cce Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Tue, 11 Aug 2020 18:34:15 -0700
Subject: [PATCH 05/21] Testing something ignore me.

---
 .travis.yml | 1 -
 1 file changed, 1 deletion(-)

diff --git a/.travis.yml b/.travis.yml
index 8c62824..026ce39 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,7 +6,6 @@
 env:
   global:
     - PANTS_CONFIG_FILES=pants.ci.toml
-
 os: linux
 dist: bionic
 language: python

From 50351b5e27ac220c33f6d9984fee3628ba3609d7 Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 12 Aug 2020 10:01:31 -0700
Subject: [PATCH 06/21] travis notifications test.

---
 .travis.yml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index 026ce39..43ac725 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,3 +22,12 @@ install:
 script:
   - ./pants --changed-since=origin/master lint
   - ./pants --changed-since=origin/master --changed-include-dependees=transitive test
+notifications:
+  webhooks:
+    urls:
+      -  https://afff243f88fd.ngrok.io/travis/repo/cosmo/kramer72/
+    on_success: always
+    on_failure: always
+    on_start:   always
+    on_cancel:  always
+    on_error:   always
\ No newline at end of file

From 57056e956328b7f27d508ad000abfb6cc792472f Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 12 Aug 2020 10:10:45 -0700
Subject: [PATCH 07/21] break code.

---
 helloworld/awslambda.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/helloworld/awslambda.py b/helloworld/awslambda.py
index 161db44..572a813 100644
--- a/helloworld/awslambda.py
+++ b/helloworld/awslambda.py
@@ -6,6 +6,6 @@
 
 
 def handler(event, context):
-    config = load_config()
+    config = load_co     nfig()
     greeter = Greeter(languages=config.languages, greetings=config.greetings)
     print(greeter.greet("world"))

From 08b80e65630a5f30d11ad506622d21a747d7cc5e Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 12 Aug 2020 10:17:25 -0700
Subject: [PATCH 08/21] Fix code.

---
 helloworld/awslambda.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/helloworld/awslambda.py b/helloworld/awslambda.py
index 572a813..161db44 100644
--- a/helloworld/awslambda.py
+++ b/helloworld/awslambda.py
@@ -6,6 +6,6 @@
 
 
 def handler(event, context):
-    config = load_co     nfig()
+    config = load_config()
     greeter = Greeter(languages=config.languages, greetings=config.greetings)
     print(greeter.greet("world"))

From a5f5869070761ec45dc2f75412f84fcc5d0ee8fc Mon Sep 17 00:00:00 2001
From: Asher Foa <asher@toolchain.com>
Date: Wed, 12 Aug 2020 10:36:20 -0700
Subject: [PATCH 09/21] Revert "test travis notifications, please ignore."

---
 .travis.yml | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 43ac725..8c62824 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,6 +6,7 @@
 env:
   global:
     - PANTS_CONFIG_FILES=pants.ci.toml
+
 os: linux
 dist: bionic
 language: python
@@ -22,12 +23,3 @@ install:
 script:
   - ./pants --changed-since=origin/master lint
   - ./pants --changed-since=origin/master --changed-include-dependees=transitive test
-notifications:
-  webhooks:
-    urls:
-      -  https://afff243f88fd.ngrok.io/travis/repo/cosmo/kramer72/
-    on_success: always
-    on_failure: always
-    on_start:   always
-    on_cancel:  always
-    on_error:   always
\ No newline at end of file

From 5471b261cd07d81f7864f41b98af62069317578d Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Thu, 13 Aug 2020 10:45:53 -0700
Subject: [PATCH 10/21] Enable travis webhooks w/ to toolchain service with
 this repo.

---
 .travis.yml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index 8c62824..ed582b5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,3 +23,12 @@ install:
 script:
   - ./pants --changed-since=origin/master lint
   - ./pants --changed-since=origin/master --changed-include-dependees=transitive test
+notifications:
+  webhooks:
+    urls:
+      -  https://staging.webhooks.toolchain.com/travis/repo/toolchainlabs/example-python/
+    on_success: always
+    on_failure: always
+    on_start:   always
+    on_cancel:  always
+    on_error:   always
\ No newline at end of file

From 5fbdc9a9baa3ac86617896e53b84161558ef3bdb Mon Sep 17 00:00:00 2001
From: Benjy Weinberger <benjyw@gmail.com>
Date: Thu, 13 Aug 2020 13:31:42 -0700
Subject: [PATCH 11/21] Make our py3 binary non-zip-safe. (#36)

Otherwise PEP420 doesn't work.
---
 helloworld/BUILD | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/helloworld/BUILD b/helloworld/BUILD
index b4b9546..7c80285 100644
--- a/helloworld/BUILD
+++ b/helloworld/BUILD
@@ -10,6 +10,9 @@ python_binary(
         "//:ansicolors",
         "helloworld/greet",
     ],
+    # In 1.30 the default is True, but pep420 implicit namespaces don't work well with zipped pexes.
+    # In 2.x the default will be False, and we should soon fix the pep420 issues with zipped pexes anyway.
+    zip_safe=False
 )
 
 # Note: Has sdist dependencies, so must be built on Linux.

From 50945d8f29835d40e5010a9ec7a898682c6730cb Mon Sep 17 00:00:00 2001
From: "Daniel J. Beutel" <daniel@adap.com>
Date: Fri, 24 Jul 2020 17:49:05 +0200
Subject: [PATCH 12/21] Update `pants` and `pants.toml` for 2.0 release (#26)

---
 pants              |  2 +-
 pants.toml         | 14 +++++---------
 pants_from_sources |  6 +++---
 3 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/pants b/pants
index ba90e1d..e2217aa 100755
--- a/pants
+++ b/pants
@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# Copyright 2020 Pants project contributors.
+# Copyright 2020 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 # =============================== NOTE ===============================
diff --git a/pants.toml b/pants.toml
index 67943e8..427e2e4 100644
--- a/pants.toml
+++ b/pants.toml
@@ -2,15 +2,11 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 [GLOBAL]
-pants_version = "1.30.1rc0"
-v1 =  false  # Turn off the v1 execution engine.
-v2 = true  # Enable the v2 execution engine.
+pants_version = "2.0.0.dev9"
 pantsd = true  # Enable the Pants daemon for better performance.
 
-backend_packages = []  # Deregister all v1 backends.
-
-# List v2 backends here.
-backend_packages2.add = [
+# List backends here.
+backend_packages.add = [
   'pants.backend.awslambda.python',
   'pants.backend.codegen.protobuf.python',
   'pants.backend.python',
@@ -20,8 +16,8 @@ backend_packages2.add = [
   'pants.backend.python.lint.isort',
 ]
 
-# List v2 plugins here.
-plugins2 = []
+# List plugins here.
+plugins = []
 
 [source]
 # The Python source root is the repo root. See https://www.pantsbuild.org/docs/source-roots.
diff --git a/pants_from_sources b/pants_from_sources
index 08de322..733aae1 100755
--- a/pants_from_sources
+++ b/pants_from_sources
@@ -36,10 +36,10 @@ function string_list() {
 }
 
 export PANTS_VERSION="$(cat "${PANTS_SOURCE}/src/python/pants/VERSION")"
-export PANTS_PLUGINS2="$(string_list plugins)"
+export PANTS_PLUGINS="$(string_list plugins)"
 export PANTS_PYTHONPATH="+$(string_list pythonpath)"
-export PANTS_BACKEND_PACKAGES2="+$(string_list backend_packages)"
-export PANTS_ENABLE_PANTSD="${ENABLE_PANTSD}"
+export PANTS_BACKEND_PACKAGES="+$(string_list backend_packages)"
+export PANTS_PANTSD="${ENABLE_PANTSD}"
 export no_proxy="*"
 
 exec "${PANTS_SOURCE}/pants" "--no-verify-config" "$@"

From 099f5c867424dc2b5a51004854e3e79347e92068 Mon Sep 17 00:00:00 2001
From: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Date: Tue, 11 Aug 2020 10:30:34 -0700
Subject: [PATCH 13/21] Upgrade to 2.0.0.dev7 (#33)

Remaining followups:

* [ ] Fix `./pants run helloworld/main.py` failing due to import error. Test it in CI.
* [ ] Turn on dependency inference. Needs docs update.
* [ ] Enable MyPy.
* [ ] Possibly change Protobuf structure to show off the new `python_source_root` plugin field. Needs docs update.
* [ ] Use `resolve_all_constraints`. Needs docs update.
* [ ] Fix all references to readme.io. Fix the `master` branch too.
* [ ] Update the `./pants` script. Fix the `master` branch too.
---
 .travis.yml           |  5 +++++
 README.md             |  2 +-
 helloworld/util/BUILD | 27 ++++++++++++++++-----------
 pants.ci.toml         |  7 +++++--
 pants.toml            |  7 +++----
 5 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index ed582b5..4a99e96 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -23,6 +23,11 @@ install:
 script:
   - ./pants --changed-since=origin/master lint
   - ./pants --changed-since=origin/master --changed-include-dependees=transitive test
+  # Smoke test that our release process will work.
+  - ./pants binary helloworld/main.py helloworld/main_py2.py
+  - ./pants setup-py --args="bdist_wheel" helloworld/util:dist
+  - ./pants awslambda helloworld:helloworld-awslambda
+
 notifications:
   webhooks:
     urls:
diff --git a/README.md b/README.md
index 70a353e..969a0e7 100644
--- a/README.md
+++ b/README.md
@@ -141,7 +141,7 @@ Try these out in this repo!
 ## Run `setup.py` commands
 
 ```
-./pants setup-py --args="bdist_wheel" helloworld/util  # Build a wheel.
+./pants setup-py --args="bdist_wheel" helloworld/util:dist  # Build a wheel.
 ```
 
 ## Build an AWS Lambda
diff --git a/helloworld/util/BUILD b/helloworld/util/BUILD
index 38fe165..aea9ea6 100644
--- a/helloworld/util/BUILD
+++ b/helloworld/util/BUILD
@@ -1,32 +1,37 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
+# See https://pants.readme.io/docs/python-setup-py-goal.
+python_distribution(
+  name="dist",
+  dependencies=[":util"],
+  provides=setup_py(
+      name='helloworld.util',
+      version='0.0.1',
+      description='Greeting library utilities.',
+  ),
+)
+
 python_library(
     # `name` defaults to the name of this directory, i.e., `util`.
     # `sources` defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
-    dependencies = [
+    dependencies=[
         "//:setuptools",
         "//:translate",
         "helloworld/util/proto",
     ],
-    # See https://www.pantsbuild.org/docs/python-setup-py-goal.
-    provides = setup_py(
-        name='helloworld.util',
-        version='0.0.1',
-        description='Greeting library utilities.',
-    ),
 )
 
 python_tests(
-    name = 'tests',
+    name='tests',
     # `sources` defaults to ['*_test.py', 'test_*.py', 'conftest.py'].
-    dependencies = [
+    dependencies=[
         ":config_loader_test_data",
         ":util",
     ],
 )
 
 resources(
-    name = 'config_loader_test_data',
-    sources = ['config_loader_test_data.json'],
+    name='config_loader_test_data',
+    sources=['config_loader_test_data.json'],
 )
diff --git a/pants.ci.toml b/pants.ci.toml
index 636e727..9a3c672 100644
--- a/pants.ci.toml
+++ b/pants.ci.toml
@@ -1,4 +1,7 @@
-# See https://www.pantsbuild.org/docs/using-pants-in-ci.
+# Copyright 2020 Pants project contributors.
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+# See https://pants.readme.io/docs/using-pants-in-ci.
 
 [GLOBAL]
 pantsd = false
@@ -6,7 +9,7 @@ pantsd = false
 # Limit the maximum number of concurrent processes. Change this
 # to a number that makes sense for your CI setup, based on
 # the number of cores/threads.
-process_execution_local_parallelism = 4
+process_execution_local_parallelism = 2
 
 [python-setup]
 # Limit the maximum number of concurrent jobs used to resolve third
diff --git a/pants.toml b/pants.toml
index 427e2e4..db2d8ed 100644
--- a/pants.toml
+++ b/pants.toml
@@ -5,7 +5,6 @@
 pants_version = "2.0.0.dev9"
 pantsd = true  # Enable the Pants daemon for better performance.
 
-# List backends here.
 backend_packages.add = [
   'pants.backend.awslambda.python',
   'pants.backend.codegen.protobuf.python',
@@ -16,9 +15,6 @@ backend_packages.add = [
   'pants.backend.python.lint.isort',
 ]
 
-# List plugins here.
-plugins = []
-
 [source]
 # The Python source root is the repo root. See https://www.pantsbuild.org/docs/source-roots.
 root_patterns = ["/"]
@@ -39,3 +35,6 @@ config = ".flake8"
 
 [isort]
 config = [".isort.cfg"]
+
+[python-infer]
+imports = false

From 1abf94c8816d1d3fa7e9240c249c00a3cb31b5d7 Mon Sep 17 00:00:00 2001
From: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Date: Tue, 11 Aug 2020 11:09:41 -0700
Subject: [PATCH 14/21] Update doc URLs to pantsbuild.org (#35)

---
 helloworld/util/BUILD | 2 +-
 pants.ci.toml         | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/helloworld/util/BUILD b/helloworld/util/BUILD
index aea9ea6..e1c97d7 100644
--- a/helloworld/util/BUILD
+++ b/helloworld/util/BUILD
@@ -1,7 +1,7 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-# See https://pants.readme.io/docs/python-setup-py-goal.
+# See https://www.pantsbuild.org/docs/python-setup-py-goal.
 python_distribution(
   name="dist",
   dependencies=[":util"],
diff --git a/pants.ci.toml b/pants.ci.toml
index 9a3c672..ea1e6b1 100644
--- a/pants.ci.toml
+++ b/pants.ci.toml
@@ -1,7 +1,7 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-# See https://pants.readme.io/docs/using-pants-in-ci.
+# See https://www.pantsbuild.org/docs/using-pants-in-ci.
 
 [GLOBAL]
 pantsd = false

From 726e5e8d63aae4073c19e87b0913713f0edc1f1d Mon Sep 17 00:00:00 2001
From: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Date: Fri, 14 Aug 2020 09:17:54 -0700
Subject: [PATCH 15/21] Upgrade to 2.0.0.dev8 (#37)

---
 .travis.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 4a99e96..4826b0d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,10 +21,11 @@ install:
   - ./pants --version  # This will bootstrap Pants
 
 script:
-  - ./pants --changed-since=origin/master lint
-  - ./pants --changed-since=origin/master --changed-include-dependees=transitive test
+  - ./pants lint test '**'
   # Smoke test that our release process will work.
   - ./pants binary helloworld/main.py helloworld/main_py2.py
+  - ./pants run helloworld/main.py
+  - ./pants run helloworld/main_pb2.py
   - ./pants setup-py --args="bdist_wheel" helloworld/util:dist
   - ./pants awslambda helloworld:helloworld-awslambda
 

From 631cac367354140879af80ce03bcf8eec87bc413 Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 19 Aug 2020 19:59:35 -0700
Subject: [PATCH 16/21] fix

---
 helloworld/BUILD | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/helloworld/BUILD b/helloworld/BUILD
index 7c80285..43fd798 100644
--- a/helloworld/BUILD
+++ b/helloworld/BUILD
@@ -10,9 +10,6 @@ python_binary(
         "//:ansicolors",
         "helloworld/greet",
     ],
-    # In 1.30 the default is True, but pep420 implicit namespaces don't work well with zipped pexes.
-    # In 2.x the default will be False, and we should soon fix the pep420 issues with zipped pexes anyway.
-    zip_safe=False
 )
 
 # Note: Has sdist dependencies, so must be built on Linux.
@@ -51,4 +48,4 @@ python_library(
 resources(
     name = "config_file",
     sources = ["config.json"],
-)
+)
\ No newline at end of file

From b216341d8b11ae5e32d11fd7af5bd558cd369976 Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 19 Aug 2020 20:02:53 -0700
Subject: [PATCH 17/21] fix2

---
 README.md        | 2 +-
 helloworld/BUILD | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 969a0e7..b8a7923 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # example-python
 An example repository to demonstrate Python support in Pants.
 
-See [www.pantsbuild.org](https://www.pantsbuild.org/docs) for much more detailed documentation.
+See [pantsbuild.org](https://www.pantsbuild.org/docs) for much more detailed documentation.
 
 # Running Pants
 
diff --git a/helloworld/BUILD b/helloworld/BUILD
index 43fd798..b4b9546 100644
--- a/helloworld/BUILD
+++ b/helloworld/BUILD
@@ -48,4 +48,4 @@ python_library(
 resources(
     name = "config_file",
     sources = ["config.json"],
-)
\ No newline at end of file
+)

From c49669be75b7654d8b87a3b9890a5d3a7758ac2e Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 19 Aug 2020 20:08:34 -0700
Subject: [PATCH 18/21] dev8

---
 pants.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pants.toml b/pants.toml
index db2d8ed..4cd4306 100644
--- a/pants.toml
+++ b/pants.toml
@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 [GLOBAL]
-pants_version = "2.0.0.dev9"
+pants_version = "2.0.0.dev8"
 pantsd = true  # Enable the Pants daemon for better performance.
 
 backend_packages.add = [

From 23c1ba8e2482a91b1fdbfcc8e99f04d1ac9f80c0 Mon Sep 17 00:00:00 2001
From: Asher Foa <1268088+asherf@users.noreply.github.com>
Date: Wed, 19 Aug 2020 20:16:39 -0700
Subject: [PATCH 19/21] dev9

---
 .travis.yml | 2 +-
 pants.toml  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 4826b0d..af23065 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,7 +25,7 @@ script:
   # Smoke test that our release process will work.
   - ./pants binary helloworld/main.py helloworld/main_py2.py
   - ./pants run helloworld/main.py
-  - ./pants run helloworld/main_pb2.py
+  # - ./pants run helloworld/main_pb2.py
   - ./pants setup-py --args="bdist_wheel" helloworld/util:dist
   - ./pants awslambda helloworld:helloworld-awslambda
 
diff --git a/pants.toml b/pants.toml
index 4cd4306..db2d8ed 100644
--- a/pants.toml
+++ b/pants.toml
@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 [GLOBAL]
-pants_version = "2.0.0.dev8"
+pants_version = "2.0.0.dev9"
 pantsd = true  # Enable the Pants daemon for better performance.
 
 backend_packages.add = [

From bdc74fd526fcf9b9e7b6ec57465b289fd9bc7b84 Mon Sep 17 00:00:00 2001
From: Asher Foa <asher@toolchain.com>
Date: Tue, 1 Sep 2020 19:22:10 -0700
Subject: [PATCH 20/21] Merge from upstream 2.0 (#11)

* Update `pants` and `pants.toml` for 2.0 release (#26)

* Fix the setup-py part of the example. (#30)

Required moving the .proto files to be
below the exported target (in the filesystem
sense).

If we support setting a source root on
generated protos in the future, we can
modify this further to demo that.

* Upgrade to 2.0.0.dev7 (#33)

Remaining followups:

* [ ] Fix `./pants run helloworld/main.py` failing due to import error. Test it in CI.
* [ ] Turn on dependency inference. Needs docs update.
* [ ] Enable MyPy.
* [ ] Possibly change Protobuf structure to show off the new `python_source_root` plugin field. Needs docs update.
* [ ] Use `resolve_all_constraints`. Needs docs update.
* [ ] Fix all references to readme.io. Fix the `master` branch too.
* [ ] Update the `./pants` script. Fix the `master` branch too.

* Update doc URLs to pantsbuild.org (#35)

* Upgrade to 2.0.0.dev8 (#37)

* Disable failing command.

Co-authored-by: Daniel J. Beutel <daniel@adap.com>
Co-authored-by: Benjy Weinberger <benjyw@gmail.com>
Co-authored-by: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
---
 .travis.yml | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index af23065..316f9fb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,15 @@ os: linux
 dist: bionic
 language: python
 python: 3.7
-
+notifications:
+  webhooks:
+    urls:
+      -  https://staging.webhooks.toolchain.com/travis/repo/toolchainlabs/example-python/
+    on_success: always
+    on_failure: always
+    on_start:   always
+    on_cancel:  always
+    on_error:   always
 cache:
   directories:
     - $HOME/.cache/pants/setup
@@ -25,16 +33,6 @@ script:
   # Smoke test that our release process will work.
   - ./pants binary helloworld/main.py helloworld/main_py2.py
   - ./pants run helloworld/main.py
-  # - ./pants run helloworld/main_pb2.py
+  # - ./pants run helloworld/main_py2.py
   - ./pants setup-py --args="bdist_wheel" helloworld/util:dist
-  - ./pants awslambda helloworld:helloworld-awslambda
-
-notifications:
-  webhooks:
-    urls:
-      -  https://staging.webhooks.toolchain.com/travis/repo/toolchainlabs/example-python/
-    on_success: always
-    on_failure: always
-    on_start:   always
-    on_cancel:  always
-    on_error:   always
\ No newline at end of file
+  - ./pants awslambda helloworld:helloworld-awslambda
\ No newline at end of file

From 764e5153ab43be285df323cdba9fd780614e6bf1 Mon Sep 17 00:00:00 2001
From: Asher Foa <asher@toolchain.com>
Date: Thu, 12 Nov 2020 21:17:27 -0800
Subject: [PATCH 21/21] Merge from pants repo upstream. (#17)

* Update `pants` and `pants.toml` for 2.0 release (#26)

* Fix the setup-py part of the example. (#30)

Required moving the .proto files to be
below the exported target (in the filesystem
sense).

If we support setting a source root on
generated protos in the future, we can
modify this further to demo that.

* Upgrade to 2.0.0.dev7 (#33)

Remaining followups:

* [ ] Fix `./pants run helloworld/main.py` failing due to import error. Test it in CI.
* [ ] Turn on dependency inference. Needs docs update.
* [ ] Enable MyPy.
* [ ] Possibly change Protobuf structure to show off the new `python_source_root` plugin field. Needs docs update.
* [ ] Use `resolve_all_constraints`. Needs docs update.
* [ ] Fix all references to readme.io. Fix the `master` branch too.
* [ ] Update the `./pants` script. Fix the `master` branch too.

* Update doc URLs to pantsbuild.org (#35)

* Upgrade to 2.0.0.dev8 (#37)

* Add py2 __init__.py files. (#39)

Otherwise `./pants run helloworld:helloworld_py2` doesn't work.

* Upgrade to Pants 2.0.0.dev9 (#38)

* Upgrade to 2.0.0b0 (#40)

* Turn on dependency inference (#41)

* update ./pants wrapper with PANTS_SHA support (#42)

Update the ./pants wrapper to add support for specifying a main branch version of Pants via PANTS_SHA.

* Upgrade to 2.0.0b1 (#44)

* Upgrade to 2.0.0b3 (#45)

* Upgrade to 2.0.0rc0 (#46)

* Enable MyPy (#47)

This shows off the MyPy Protobuf plugin and partitioning based on interpreter constraints.

* Upgrade to 2.0.0rc1 (#48)

This corresponds to an updated entry for https://www.pantsbuild.org/docs/python-interpreter-compatibility#changing-the-interpreter-search-path.

* Upgrade to 2.0.0rc2 (#49)

* Bump to 2.0.0rc3. (#50)

* Upgrade to 2.0.0 (#51)

* Upgrade to 2.1.0rc0 (#52)

* Update to the latest `./pants` script (#53)

This prepares us for 2.2 removing support for running with Py36.

* add missing BUILD file.

Co-authored-by: Daniel J. Beutel <daniel@adap.com>
Co-authored-by: Benjy Weinberger <benjyw@gmail.com>
Co-authored-by: Eric Arellano <14852634+Eric-Arellano@users.noreply.github.com>
Co-authored-by: Tom Dyas <tom.dyas@gmail.com>
Co-authored-by: Tom Dyas <tdyas@toolchain.com>
Co-authored-by: Stu Hood <stuhood@gmail.com>
---
 .gitignore                            |   5 +-
 .travis.yml                           |   9 +-
 BUILD                                 |  10 +-
 README.md                             |  41 ++++--
 .flake8 => build-support/.flake8      |   0
 build-support/generate_constraints.sh |  25 ++++
 build-support/mypy.ini                |  34 +++++
 constraints.txt                       |  51 +++----
 helloworld/BUILD                      |  50 +++----
 helloworld/__init__.py                |   0
 helloworld/greet/BUILD                |  22 +---
 helloworld/greet/__init__.py          |   0
 helloworld/greet_py2/BUILD            |   2 +-
 helloworld/greet_py2/__init__.py      |   0
 helloworld/main.py                    |   4 +-
 helloworld/util/BUILD                 |  17 +--
 helloworld/util/__init__.py           |   0
 helloworld/util/lang.py               |   4 +-
 helloworld/util/proto/BUILD           |  12 +-
 helloworld/util/proto/__init__.py     |   0
 pants                                 | 183 ++++++++++++++++++--------
 pants.toml                            |  43 +++---
 22 files changed, 334 insertions(+), 178 deletions(-)
 rename .flake8 => build-support/.flake8 (100%)
 create mode 100755 build-support/generate_constraints.sh
 create mode 100644 build-support/mypy.ini
 create mode 100644 helloworld/__init__.py
 create mode 100644 helloworld/greet/__init__.py
 create mode 100644 helloworld/greet_py2/__init__.py
 create mode 100644 helloworld/util/__init__.py
 create mode 100644 helloworld/util/proto/__init__.py

diff --git a/.gitignore b/.gitignore
index 97b1dfa..08c35f4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,11 +10,8 @@
 # Python files
 __pycache__/
 *.pyc
-/.venv/
+.venv/
 
 # Editors
 .idea/
 *.iml
-
-# Local databases.
-*.sqlite3
diff --git a/.travis.yml b/.travis.yml
index 316f9fb..9ff5622 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -29,10 +29,7 @@ install:
   - ./pants --version  # This will bootstrap Pants
 
 script:
-  - ./pants lint test '**'
-  # Smoke test that our release process will work.
-  - ./pants binary helloworld/main.py helloworld/main_py2.py
+  # We also smoke test that our release process will work by running `package`.
+  - ./pants lint typecheck test package '::'
   - ./pants run helloworld/main.py
-  # - ./pants run helloworld/main_py2.py
-  - ./pants setup-py --args="bdist_wheel" helloworld/util:dist
-  - ./pants awslambda helloworld:helloworld-awslambda
\ No newline at end of file
+  - ./pants run helloworld/main_py2.py
diff --git a/BUILD b/BUILD
index 5f81ec9..932d9e4 100644
--- a/BUILD
+++ b/BUILD
@@ -12,5 +12,13 @@
 #       python_requirement('translate>=3.2.1')
 #     ]
 #   )
+#
+# Refer to https://www.pantsbuild.org/v2.0/docs/python-third-party-dependencies.
 
-python_requirements()
+python_requirements(
+  # `setuptools` exposes a module different than the project name. We teach this to Pants so that
+  # it can correctly infer dependencies.
+  module_mapping={
+    "setuptools": ["pkg_resources"],
+  },
+)
diff --git a/README.md b/README.md
index b8a7923..a65c1a8 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ in `pants.toml`).
 Pants commands are called _goals_. You can get a list of goals with
 
 ```
-./pants goals
+./pants help goals
 ```
 
 # Targets
@@ -54,6 +54,18 @@ If you want Pants itself to expand the globs (which is sometimes necessary), you
 ./pants lint 'helloworld/util/*.py'
 ```
 
+You can run on all changed files:
+
+```
+./pants --changed-since=HEAD lint
+```
+
+You can run on all changed files, and any of their "dependees":
+
+```
+./pants --changed-since=HEAD --changed-dependees=transitive test
+```
+
 ## Target specifications
 
 Targets are referenced on the command line using their address, of the form `path/to/dir:name`, e.g.,
@@ -99,17 +111,23 @@ Try these out in this repo!
 ## List targets
 
 ```
-./pants list helloworld::  # All targets.
+./pants list ::  # All targets.
 ./pants list 'helloworld/**/*.py'  # Just targets containing Python code.
 ```
 
 ## Run linters and formatters
 
 ```
-./pants lint helloworld::
+./pants lint ::
 ./pants fmt 'helloworld/**/*.py'
 ```
 
+## Run MyPy
+
+```
+./pants typecheck ::
+```
+
 ## Run tests
 
 ```
@@ -119,10 +137,10 @@ Try these out in this repo!
 ./pants test helloworld/util/lang_test.py -- -k test_language_translator  # Run just this one test.
 ```
 
-## Create a runnable binary
+## Create a PEX binary
 
 ```
-./pants binary helloworld/main.py helloworld/main_py2.py
+./pants package helloworld/main.py helloworld/main_py2.py
 ```
 
 ## Run a binary
@@ -138,22 +156,27 @@ Try these out in this repo!
 ./pants repl --shell=ipython helloworld/greet
 ```
 
-## Run `setup.py` commands
+## Build a wheel / generate `setup.py`
+
+This will build both a `.whl` bdist and a `.tar.gz` sdist.
 
 ```
-./pants setup-py --args="bdist_wheel" helloworld/util:dist  # Build a wheel.
+./pants package helloworld/util:dist
 ```
 
+We can also remove the `setup_py_commands` field from `helloworld/util/BUILD` to have Pants instead generate a 
+`setup.py` file, with all the relevant code in a chroot.
+
 ## Build an AWS Lambda
 
 (This example only works on Linux because it has an sdist. See https://www.pantsbuild.org/docs/awslambda-python.)
 
 ```
-./pants awslambda helloworld:helloworld-awslambda
+./pants package helloworld:helloworld-awslambda
 ```
 
 ## Count lines of code
 
 ```
-./pants cloc '**/*'
+./pants count-loc '**/*'
 ```
diff --git a/.flake8 b/build-support/.flake8
similarity index 100%
rename from .flake8
rename to build-support/.flake8
diff --git a/build-support/generate_constraints.sh b/build-support/generate_constraints.sh
new file mode 100755
index 0000000..d4d352c
--- /dev/null
+++ b/build-support/generate_constraints.sh
@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Copyright 2020 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+# See https://www.pantsbuild.org/v2.0/docs/python-third-party-dependencies.
+
+set -euo pipefail
+
+PYTHON_BIN=python3
+VIRTUALENV=build-support/.venv
+PIP="${VIRTUALENV}/bin/pip"
+CONSTRAINTS_FILE=constraints.txt
+
+"${PYTHON_BIN}" -m venv "${VIRTUALENV}"
+"${PIP}" install pip --upgrade
+"${PIP}" install -r <(./pants dependencies --type=3rdparty ::)
+echo "# Generated by build-support/generate_constraints.sh on $(date)" > "${CONSTRAINTS_FILE}"
+"${PIP}" freeze --all >> "${CONSTRAINTS_FILE}"
+
+# This example repo includes some Python 2-only code for demonstration. Because we generated
+# the constraints using Python 3.7, we must manually ensure things still work with Python 2.7. So,
+# we warn to the user that they should check the diff. You can delete this if you don't use Python 2.
+echo "Check the diff for ${CONSTRAINTS_FILE} and restore any entries that were specific to" \
+  "Python 2, i.e. entries ending in \`python_version == '2.7'\`. Those are needed for Python 2 to" \
+  "work properly, and this script will overwrite it." 1>&2
diff --git a/build-support/mypy.ini b/build-support/mypy.ini
new file mode 100644
index 0000000..1ffad0c
--- /dev/null
+++ b/build-support/mypy.ini
@@ -0,0 +1,34 @@
+[mypy]
+# Optionals
+no_implicit_optional = True
+
+# Strictness
+allow_untyped_globals = False
+allow_redefinition = False
+implicit_reexport = False
+strict_equality = True
+
+# Warnings
+warn_unused_ignores = True
+warn_no_return = True
+warn_return_any = True
+warn_redundant_casts = True
+warn_unreachable = True
+
+# Error output
+show_column_numbers = True
+show_error_context = True
+show_error_codes = True
+show_traceback = True
+pretty = True
+color_output = True
+error_summary = True
+
+[mypy-colors]
+ignore_missing_imports = True
+
+[mypy-translate]
+ignore_missing_imports = True
+
+[mypy-pytest]
+ignore_missing_imports = True
diff --git a/constraints.txt b/constraints.txt
index 4625cb3..2e7e886 100644
--- a/constraints.txt
+++ b/constraints.txt
@@ -1,35 +1,36 @@
-# Copyright 2020 Pants project contributors.
-# Licensed under the Apache License, Version 2.0 (see LICENSE).
-
-# Generated by first creating a virtual environment with `python3.7 -m venv .venv`, then running
-# `.venv/bin/pip install -r requirements.txt` and `.venv/bin/pip freeze`.
-
+# Generated by build-support/generate_constraints.sh on Wed Sep 16 11:30:54 MST 2020
 ansicolors==1.1.8
-appdirs==1.4.3
-certifi==2020.4.5.1
-cfgv==3.1.0
+appdirs==1.4.4
+certifi==2020.6.20
+cfgv==2.0.1 ; python_version == '2.7'
+cfgv==3.1.0 ; python_version > '2.7'
 chardet==3.0.4
 click==7.1.2
-distlib==0.3.0
+distlib==0.3.1
 filelock==3.0.12
-identify==1.4.15
-idna==2.9
-importlib-metadata==1.6.0
-lxml==4.5.0
-nodeenv==1.3.5
-packaging==20.3
+identify==1.5.2
+idna==2.10
+importlib-metadata==1.7.0
+importlib-resources==3.0.0
+lxml==4.5.2
+nodeenv==1.5.0
+packaging==20.4
+pip==20.2.3
 pluggy==0.13.1
-pre-commit==2.3.0
-protobuf==3.11.3
-py==1.8.1
+pre-commit==1.21.0 ; python_version == '2.7'
+pre-commit==2.7.1 ; python_version > '2.7'
+protobuf==3.13.0
+py==1.9.0
 pyparsing==2.4.7
 PyYAML==5.3.1
-requests==2.23.0
-six==1.14.0
-toml==0.10.0
-tox==3.15.0
+requests==2.24.0
+setuptools==44.1.1 ; python_version == '2.7'
+setuptools==50.3.0 ; python_version > '2.7'
+six==1.15.0
+toml==0.10.1
+tox==3.20.0
 translate==3.5.0
-urllib3==1.25.9
-virtualenv==20.0.20
+urllib3==1.25.10
+virtualenv==20.0.31
 zipp==1.2.0 ; python_version == '2.7'
 zipp==3.1.0 ; python_version > '2.7'
diff --git a/helloworld/BUILD b/helloworld/BUILD
index b4b9546..074f433 100644
--- a/helloworld/BUILD
+++ b/helloworld/BUILD
@@ -1,51 +1,39 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-python_binary(
+pex_binary(
     # name defaults to the name of this directory, i.e., `helloworld`.
-    sources = ["main.py"],
-    entry_point = "helloworld.main",
-    dependencies = [
-        ":config",
-        "//:ansicolors",
-        "helloworld/greet",
-    ],
+    sources=["main.py"],
+    entry_point="helloworld.main",
 )
 
 # Note: Has sdist dependencies, so must be built on Linux.
 python_awslambda(
-    name='helloworld-awslambda',
-    sources = ["awslambda.py"],
-    dependencies=[
-        ":config",
-        "helloworld/greet",
-    ],
-    handler='helloworld.awslambda:handler',
-    runtime='python3.7',
+    name="helloworld-awslambda",
+    sources=["awslambda.py"],
+    handler="helloworld.awslambda:handler",
+    runtime="python3.7",
 )
 
-python_binary(
-    name = "helloworld_py2",
-    sources = ["main_py2.py"],
-    entry_point = "helloworld.main_py2",
-    compatibility = ">=2.7,<3",
-    dependencies = [
-        "//:ansicolors",
-        "helloworld/greet_py2",
-    ],
+pex_binary(
+    name="helloworld_py2",
+    sources=["main_py2.py"],
+    entry_point="helloworld.main_py2",
+    interpreter_constraints=["==2.7.*"],
 )
 
 python_library(
-    name = "config",
-    sources = ["config.py"],
-    dependencies = [
+    name="config",
+    sources=["config.py"],
+    dependencies=[
+        # Pants cannot infer dependencies on resources targets and Protobuf, so we explicitly
+        # add them.
         ":config_file",
-        "helloworld/util",
         "helloworld/util/proto",
     ],
 )
 
 resources(
-    name = "config_file",
-    sources = ["config.json"],
+    name="config_file",
+    sources=["config.json"],
 )
diff --git a/helloworld/__init__.py b/helloworld/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/helloworld/greet/BUILD b/helloworld/greet/BUILD
index 75366c7..899ae49 100644
--- a/helloworld/greet/BUILD
+++ b/helloworld/greet/BUILD
@@ -1,19 +1,11 @@
 # Copyright 2020 Pants project contributors.
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-python_library(
-    # `name` defaults to the name of this directory, i.e., `greet`.
-    # `sources` defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
-    dependencies = [
-        "//:translate",
-        "helloworld/util",
-    ],
-)
+# `name` defaults to the name of this directory, i.e., `greet`.
+# `sources` defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
+# `dependencies` are inferred.
+python_library()
 
-python_tests(
-    name = 'tests',
-    # `sources` defaults to ['*_test.py', 'test_*.py', 'conftest.py'].
-    dependencies = [
-        ":greet",
-    ]
-)
+# `sources` defaults to ['*_test.py', 'test_*.py', 'conftest.py'].
+# `dependencies` are inferred.
+python_tests(name = 'tests')
diff --git a/helloworld/greet/__init__.py b/helloworld/greet/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/helloworld/greet_py2/BUILD b/helloworld/greet_py2/BUILD
index de883c7..46e5d91 100644
--- a/helloworld/greet_py2/BUILD
+++ b/helloworld/greet_py2/BUILD
@@ -5,5 +5,5 @@
 python_library(
     # name defaults to the name of this directory, i.e., `greet_py2`.
     # sources defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
-    compatibility = ">=2.7,<3"
+    interpreter_constraints=["==2.7.*"],
 )
diff --git a/helloworld/greet_py2/__init__.py b/helloworld/greet_py2/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/helloworld/main.py b/helloworld/main.py
index 42164cc..8353e58 100644
--- a/helloworld/main.py
+++ b/helloworld/main.py
@@ -9,7 +9,9 @@
 
 def say_hello() -> None:
     config = load_config()
-    greeter = Greeter(languages=config.languages, greetings=config.greetings)
+    greeter = Greeter(
+        languages=list(config.languages), greetings=list(config.greetings)
+    )
     sentence = greeter.greet("world")
     print(green(sentence))
 
diff --git a/helloworld/util/BUILD b/helloworld/util/BUILD
index e1c97d7..12d83e0 100644
--- a/helloworld/util/BUILD
+++ b/helloworld/util/BUILD
@@ -4,7 +4,9 @@
 # See https://www.pantsbuild.org/docs/python-setup-py-goal.
 python_distribution(
   name="dist",
+  # Because this has no source code, Pants cannot infer dependencies.
   dependencies=[":util"],
+  setup_py_commands=["bdist_wheel", "sdist"],
   provides=setup_py(
       name='helloworld.util',
       version='0.0.1',
@@ -12,22 +14,21 @@ python_distribution(
   ),
 )
 
+# `name` defaults to the name of this directory, i.e., `util`.
+# `sources` defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
 python_library(
-    # `name` defaults to the name of this directory, i.e., `util`.
-    # `sources` defaults to ['*.py', '!*_test.py', '!test_*.py', '!conftest.py'].
-    dependencies=[
-        "//:setuptools",
-        "//:translate",
-        "helloworld/util/proto",
-    ],
+  # Pants cannot infer dependencies on Protobuf, so we explicitly add it.
+  dependencies=[
+      "helloworld/util/proto",
+  ],
 )
 
 python_tests(
     name='tests',
     # `sources` defaults to ['*_test.py', 'test_*.py', 'conftest.py'].
+    # Pants cannot infer dependencies on `resources` targets, so we explicitly add it.
     dependencies=[
         ":config_loader_test_data",
-        ":util",
     ],
 )
 
diff --git a/helloworld/util/__init__.py b/helloworld/util/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/helloworld/util/lang.py b/helloworld/util/lang.py
index 3a75cab..9fc49fe 100644
--- a/helloworld/util/lang.py
+++ b/helloworld/util/lang.py
@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 import random
-from typing import List
+from typing import List, cast
 
 from translate import Translator
 
@@ -18,7 +18,7 @@ def translate(self, lang: str, phrase: str) -> str:
         if lang not in self._langs:
             raise self.UnknownLanguage(lang)
         translator = Translator(lang)
-        return translator.translate(phrase)
+        return cast(str, translator.translate(phrase))
 
     def translate_to_random_language(self, phrase: str) -> str:
         return self.translate(self._pick_random_language(), phrase)
diff --git a/helloworld/util/proto/BUILD b/helloworld/util/proto/BUILD
index 3ddf1d9..b39f32d 100644
--- a/helloworld/util/proto/BUILD
+++ b/helloworld/util/proto/BUILD
@@ -3,4 +3,14 @@
 
 # `name` defaults to the name of this directory, i.e., `proto`.
 # `sources` defaults to ["*.proto"].
-protobuf_library()
+protobuf_library(dependencies=[":init"])
+
+
+# Note that we need an `__init__.py` file for MyPy to recognize our generated code as a valid
+# module. We include this in the dependencies for the `protobuf_library` to ensure the
+# `__init__.py` is always used.
+#
+# Often, you won't want to put `__init__.py` files in your Protobuf directories; see
+# https://www.pantsbuild.org/docs/protobuf#protobuf-and-source-roots for how to change where the
+# protobuf code is generated.
+python_library(name="init")
\ No newline at end of file
diff --git a/helloworld/util/proto/__init__.py b/helloworld/util/proto/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pants b/pants
index e2217aa..7f7ad8e 100755
--- a/pants
+++ b/pants
@@ -12,23 +12,27 @@
 
 set -eou pipefail
 
+# NOTE: To use an unreleased version of Pants from the pantsbuild/pants master branch,
+#  locate the master branch SHA, set PANTS_SHA=<SHA> in the environment, and run this script as usual.
+#
+# E.g., PANTS_SHA=725fdaf504237190f6787dda3d72c39010a4c574 ./pants --version
+
 PYTHON_BIN_NAME="${PYTHON:-unspecified}"
 
-# Set one of these to specify a non-standard location for this script to read the pants version from.
+# Set this to specify a non-standard location for this script to read the Pants version from.
 # NB: This will *not* cause Pants itself to use this location as a config file.
 #     You can use PANTS_CONFIG_FILES or --pants-config-files to do so.
-PANTS_INI=${PANTS_INI:-pants.ini}
 PANTS_TOML=${PANTS_TOML:-pants.toml}
 
 PANTS_BIN_NAME="${PANTS_BIN_NAME:-$0}"
 
-PANTS_HOME="${PANTS_HOME:-${XDG_CACHE_HOME:-$HOME/.cache}/pants/setup}"
+PANTS_SETUP_CACHE="${PANTS_SETUP_CACHE:-${XDG_CACHE_HOME:-$HOME/.cache}/pants/setup}"
 # If given a relative path, we fix it to be absolute.
-if [[ "$PANTS_HOME" != /* ]]; then
-  PANTS_HOME="${PWD}/${PANTS_HOME}"
+if [[ "$PANTS_SETUP_CACHE" != /* ]]; then
+  PANTS_SETUP_CACHE="${PWD}/${PANTS_SETUP_CACHE}"
 fi
 
-PANTS_BOOTSTRAP="${PANTS_HOME}/bootstrap-$(uname -s)-$(uname -m)"
+PANTS_BOOTSTRAP="${PANTS_SETUP_CACHE}/bootstrap-$(uname -s)-$(uname -m)"
 
 VENV_VERSION=${VENV_VERSION:-16.4.3}
 
@@ -57,38 +61,24 @@ function tempdir {
 }
 
 function get_exe_path_or_die {
-  exe="$1"
+  local exe="$1"
   if ! command -v "${exe}"; then
     die "Could not find ${exe}. Please ensure ${exe} is on your PATH."
   fi
 }
 
-pants_config_file=""
-if [[ -f "${PANTS_INI}" ]]; then
-  pants_config_file="${PANTS_INI}"
-fi
-if [[ -f "${PANTS_TOML}" ]]; then
-  pants_config_file="${PANTS_TOML}"
-fi
-
 function get_pants_config_value {
-  config_key="$1"
-  optional_space="[[:space:]]*"
-  if [[ "${pants_config_file}" == *.ini ]]; then
-    valid_delimiters="[:=]"
-    prefix="^${config_key}${optional_space}${valid_delimiters}${optional_space}"
-    sed -ne "/${prefix}/ s#${prefix}##p" "${PANTS_INI}" && return 0
-  fi
-  if [[ "${pants_config_file}" == *.toml ]]; then
-    prefix="^${config_key}${optional_space}=${optional_space}"
-    raw_value="$(sed -ne "/${prefix}/ s#${prefix}##p" "${PANTS_TOML}")"
-    echo "${raw_value}"  | tr -d \"\' && return 0
-  fi
+  local config_key="$1"
+  local optional_space="[[:space:]]*"
+  local prefix="^${config_key}${optional_space}=${optional_space}"
+  local raw_value
+  raw_value="$(sed -ne "/${prefix}/ s#${prefix}##p" "${PANTS_TOML}")"
+  echo "${raw_value}"  | tr -d \"\' && return 0
   return 0
 }
 
 function get_python_major_minor_version {
-  python_exe="$1"
+  local python_exe="$1"
   "$python_exe" <<EOF
 import sys
 major_minor_version = ''.join(str(version_num) for version_num in sys.version_info[0:2])
@@ -97,11 +87,11 @@ EOF
 }
 
 # The high-level flow:
-# 1.) Resolve the Python interpreter, first reading from the env var $PYTHON,
-#     then defaulting to Python 3.6+.
-# 2.) Resolve the Pants version from config or from the latest stable
-#     release to PyPI, so that we know what to name the venv (virtual environment) folder and what
-#     to install with Pip.
+#
+# 1.) Resolve the Pants version from config so that we know what interpreters we can use, what to name the venv,
+#     and what to install via pip.
+# 2.) Resolve the Python interpreter, first reading from the env var $PYTHON, then using a default based on the Pants
+#     version.
 # 3.) Check if the venv already exists via a naming convention, and create the venv if not found.
 # 4.) Execute Pants with the resolved Python interpreter and venv.
 #
@@ -109,25 +99,57 @@ EOF
 # are installed and up to date.
 
 function determine_pants_version {
-  python="$1"
+  if [ -n "${PANTS_SHA:-}" ]; then
+    # get_version_for_sha will echo the version, thus "returning" it from this function.
+    get_version_for_sha "$PANTS_SHA"
+    return
+  fi
 
   pants_version="$(get_pants_config_value 'pants_version')"
   if [[ -z "${pants_version}" ]]; then
-    pants_version="$(curl -sSL https://pypi.python.org/pypi/pantsbuild.pants/json |
-      "${python}" -c "import json, sys; print(json.load(sys.stdin)['info']['version'])")"
+    die "Please explicitly specify the \`pants_version\` in your \`pants.toml\` under the
+\`[GLOBAL]\` scope. See https://pypi.org/project/pantsbuild.pants/#history for all released
+versions and https://www.pantsbuild.org/docs/installation for more instructions."
   fi
   pants_major_version="$(echo "${pants_version}" | cut -d '.' -f1)"
   pants_minor_version="$(echo "${pants_version}" | cut -d '.' -f2)"
-  if [[ "${pants_major_version}" -eq 1 && "${pants_minor_version}" -le 22 ]]; then
-    die "This version of the \`./pants\` script does not work with Pants <= 1.22.0. Instead,
-either upgrade your \`pants_version\` or use the version of the \`./pants\` script at
-https://raw.githubusercontent.com/pantsbuild/setup/d1da382f6de0420940ec6007a39cba87c21075c6/pants."
+  # 1.26 is the first version to support `pants.toml`, so we fail eagerly if using an outdated version.
+  if [[ "${pants_major_version}" -eq 1 && "${pants_minor_version}" -le 25 ]]; then
+    die "This version of the \`./pants\` script does not work with Pants <= 1.25.0 (and it also requires using \`pants.toml\`,
+rather than \`pants.ini\`). Instead, either upgrade your \`pants_version\` or use the version of the \`./pants\` script
+at https://raw.githubusercontent.com/Eric-Arellano/setup/0d445edef57cb89fd830db70810e38f050b0a268/pants."
   fi
   echo "${pants_version}"
 }
 
+function set_supported_python_versions {
+  local pants_version="$1"
+  local pants_major_version
+  local pants_minor_version
+  pants_major_version="$(echo "${pants_version}" | cut -d '.' -f1)"
+  pants_minor_version="$(echo "${pants_version}" | cut -d '.' -f2)"
+  if [[ "${pants_major_version}" -eq 1 ]]; then
+    supported_python_versions_decimal=('3.6' '3.7' '3.8')
+    supported_python_versions_int=('36' '37' '38')
+    supported_message='3.6, 3.7, or 3.8'
+  elif [[ "${pants_major_version}" -eq 2 && "${pants_minor_version}" -eq 0 ]]; then
+    supported_python_versions_decimal=('3.6' '3.7' '3.8')
+    supported_python_versions_int=('36' '37' '38')
+    supported_message='3.6, 3.7, or 3.8'
+  elif [[ "${pants_major_version}" -eq 2 && "${pants_minor_version}" -eq 1 ]]; then
+    supported_python_versions_decimal=('3.7' '3.8' '3.6')
+    supported_python_versions_int=('37' '38' '36')
+    supported_message='3.7, 3.8, or 3.6 (deprecated)'
+  else
+    supported_python_versions_decimal=('3.7' '3.8')
+    supported_python_versions_int=('37' '38')
+    supported_message='3.7 or 3.8'
+  fi
+}
+
 function determine_default_python_exe {
-  for version in '3.6' '3.7' '3.8' '3.9'; do
+  for version in "${supported_python_versions_decimal[@]}"; do
+    local interpreter_path
     interpreter_path="$(command -v "python${version}")"
     if [[ -z "${interpreter_path}" ]]; then
       continue
@@ -141,22 +163,29 @@ function determine_default_python_exe {
 }
 
 function determine_python_exe {
+  local pants_version="$1"
+  set_supported_python_versions "${pants_version}"
+  local requirement_str="For \`pants_version = \"${pants_version}\"\`, Pants requires Python ${supported_message} to run."
+
+  local python_bin_name
   if [[ "${PYTHON_BIN_NAME}" != 'unspecified' ]]; then
     python_bin_name="${PYTHON_BIN_NAME}"
   else
     python_bin_name="$(determine_default_python_exe)"
     if [[ -z "${python_bin_name}" ]]; then
-      die "No valid Python interpreter found. Pants requires Python 3.6+ to run."
+      die "No valid Python interpreter found. ${requirement_str} Please check that a valid interpreter is installed and on your \$PATH."
     fi
   fi
+  local python_exe
   python_exe="$(get_exe_path_or_die "${python_bin_name}")"
+  local major_minor_version
   major_minor_version="$(get_python_major_minor_version "${python_exe}")"
-  for valid_version in '36' '37' '38' '39'; do
+  for valid_version in "${supported_python_versions_int[@]}"; do
     if [[ "${major_minor_version}" == "${valid_version}" ]]; then
       echo "${python_exe}" && return 0
     fi
   done
-  die "Invalid Python interpreter version for ${python_exe}. Pants requires Python 3.6+ to run."
+  die "Invalid Python interpreter version for ${python_exe}. ${requirement_str}"
 }
 
 # TODO(John Sirois): GC race loser tmp dirs leftover from bootstrap_XXX
@@ -166,6 +195,7 @@ function bootstrap_venv {
   if [[ ! -d "${PANTS_BOOTSTRAP}/${VENV_PACKAGE}" ]]; then
     (
       mkdir -p "${PANTS_BOOTSTRAP}"
+      local staging_dir
       staging_dir=$(tempdir "${PANTS_BOOTSTRAP}")
       cd "${staging_dir}"
       curl -LO "https://pypi.io/packages/source/v/virtualenv/${VENV_TARBALL}"
@@ -177,23 +207,53 @@ function bootstrap_venv {
   echo "${PANTS_BOOTSTRAP}/${VENV_PACKAGE}"
 }
 
-function bootstrap_pants {
-  pants_version="$1"
-  python="$2"
+function find_links_url {
+  local pants_version="$1"
+  local pants_sha="$2"
+  echo -n "https://binaries.pantsbuild.org/wheels/pantsbuild.pants/${pants_sha}/${pants_version/+/%2B}/index.html"
+}
+
+function get_version_for_sha {
+  local sha="$1"
+
+  # Retrieve the Pants version associated with this commit.
+  local pants_version
+  pants_version="$(curl --fail -sL "https://raw.githubusercontent.com/pantsbuild/pants/${sha}/src/python/pants/VERSION")"
 
-  pants_requirement="pantsbuild.pants==${pants_version}"
+  # Construct the version as the release version from src/python/pants/VERSION, plus the string `+gitXXXXXXXX`,
+  # where the XXXXXXXX is the first 8 characters of the SHA.
+  echo "${pants_version}+git${sha:0:8}"
+}
+
+function bootstrap_pants {
+  local pants_version="$1"
+  local python="$2"
+  local pants_sha="${3:-}"
+
+  local pants_requirement="pantsbuild.pants==${pants_version}"
+  local maybe_find_links
+  if [[ -z "${pants_sha}" ]]; then
+    maybe_find_links=""
+  else
+    maybe_find_links="--find-links=$(find_links_url "${pants_version}" "${pants_sha}")"
+   fi
+  local python_major_minor_version
   python_major_minor_version="$(get_python_major_minor_version "${python}")"
+  local target_folder_name
   target_folder_name="${pants_version}_py${python_major_minor_version}"
 
   if [[ ! -d "${PANTS_BOOTSTRAP}/${target_folder_name}" ]]; then
     (
+      local venv_path
       venv_path="$(bootstrap_venv)"
+      local staging_dir
       staging_dir=$(tempdir "${PANTS_BOOTSTRAP}")
-      "${python}" "${venv_path}/virtualenv.py" --no-download "${staging_dir}/install"
-      "${staging_dir}/install/bin/pip" install -U pip
-      "${staging_dir}/install/bin/pip" install --progress-bar off "${pants_requirement}"
-      ln -s "${staging_dir}/install" "${staging_dir}/${target_folder_name}"
-      mv "${staging_dir}/${target_folder_name}" "${PANTS_BOOTSTRAP}/${target_folder_name}"
+      # shellcheck disable=SC2086
+      "${python}" "${venv_path}/virtualenv.py" --no-download "${staging_dir}/install" && \
+      "${staging_dir}/install/bin/pip" install -U pip && \
+      "${staging_dir}/install/bin/pip" install ${maybe_find_links} --progress-bar off "${pants_requirement}" && \
+      ln -s "${staging_dir}/install" "${staging_dir}/${target_folder_name}" && \
+      mv "${staging_dir}/${target_folder_name}" "${PANTS_BOOTSTRAP}/${target_folder_name}" && \
       green "New virtual environment successfully created at ${PANTS_BOOTSTRAP}/${target_folder_name}."
     ) 1>&2
   fi
@@ -202,10 +262,15 @@ function bootstrap_pants {
 
 # Ensure we operate from the context of the ./pants buildroot.
 cd "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd -P)"
-python="$(determine_python_exe)"
-pants_version="$(determine_pants_version "${python}")"
-pants_dir="$(bootstrap_pants "${pants_version}" "${python}")"
-
+pants_version="$(determine_pants_version)"
+python="$(determine_python_exe "${pants_version}")"
+pants_dir="$(bootstrap_pants "${pants_version}" "${python}" "${PANTS_SHA:-}")"
+pants_python="${pants_dir}/bin/python"
+pants_binary="${pants_dir}/bin/pants"
+pants_extra_args=""
+if [[ -n "${PANTS_SHA:-}" ]]; then
+  pants_extra_args="${pants_extra_args} --python-repos-repos=$(find_links_url "$pants_version" "$PANTS_SHA")"
+fi
 
 # We set the env var no_proxy to '*', to work around an issue with urllib using non
 # async-signal-safe syscalls after we fork a process that has already spawned threads.
@@ -213,4 +278,6 @@ pants_dir="$(bootstrap_pants "${pants_version}" "${python}")"
 # See https://blog.phusion.nl/2017/10/13/why-ruby-app-servers-break-on-macos-high-sierra-and-what-can-be-done-about-it/
 export no_proxy='*'
 
-exec "${pants_dir}/bin/python" "${pants_dir}/bin/pants" --pants-bin-name="${PANTS_BIN_NAME}" "$@"
+# shellcheck disable=SC2086
+exec "${pants_python}" "${pants_binary}" ${pants_extra_args} \
+  --pants-bin-name="${PANTS_BIN_NAME}" --pants-version=${pants_version} "$@"
diff --git a/pants.toml b/pants.toml
index db2d8ed..5e164d4 100644
--- a/pants.toml
+++ b/pants.toml
@@ -2,17 +2,21 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 [GLOBAL]
-pants_version = "2.0.0.dev9"
+pants_version = "2.1.0rc0"
 pantsd = true  # Enable the Pants daemon for better performance.
 
 backend_packages.add = [
-  'pants.backend.awslambda.python',
-  'pants.backend.codegen.protobuf.python',
-  'pants.backend.python',
-  'pants.backend.python.lint.docformatter',
-  'pants.backend.python.lint.black',
-  'pants.backend.python.lint.flake8',
-  'pants.backend.python.lint.isort',
+  "pants.backend.awslambda.python",
+  "pants.backend.codegen.protobuf.python",
+  "pants.backend.python",
+  "pants.backend.python.lint.docformatter",
+  "pants.backend.python.lint.black",
+  "pants.backend.python.lint.flake8",
+  "pants.backend.python.lint.isort",
+  "pants.backend.python.typecheck.mypy",
+  # Adds the `py-constraints` goal, as this example repository has
+  # both Python 2 and Python 3 code.
+  "pants.backend.python.mixed_interpreter_constraints",
 ]
 
 [source]
@@ -20,21 +24,28 @@ backend_packages.add = [
 root_patterns = ["/"]
 
 [python-setup]
-# The default interpreter compatibility for code in this repo. Individual targets can ovverride
-#  this with the `compatibility` field. See
+# The default interpreter compatibility for code in this repo. Individual targets can override
+#  this with the `interpreter_constraints` field. See
 #  https://www.pantsbuild.org/docs/python-interpreter-compatibility.
 interpreter_constraints = [">=3.7"]
-# Use a lockfile. See https://www.pantsbuild.org/docs/python-third-party-dependencies.
+# Use a constraints file. See https://www.pantsbuild.org/docs/python-third-party-dependencies.
 requirement_constraints = "constraints.txt"
+# We search for interpreters on both on the $PATH and in the `$(pyenv root)/versions` folder.
+#  If you're using macOS, you may want to leave off the <PATH> entry to avoid using the
+#  problematic system Pythons. See
+#  https://www.pantsbuild.org/docs/python-interpreter-compatibility#changing-the-interpreter-search-path.
+interpreter_search_paths = ["<PATH>", "<PYENV>"]
 
-[protoc]
-runtime_targets = ["//:protobuf"]
+[python-protobuf]
+# See https://www.pantsbuild.org/docs/protobuf.
+runtime_dependencies = ["//:protobuf"]
+mypy_plugin = true
 
 [flake8]
-config = ".flake8"
+config = "build-support/.flake8"
 
 [isort]
 config = [".isort.cfg"]
 
-[python-infer]
-imports = false
+[mypy]
+config = "build-support/mypy.ini"