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Commit 46f08de

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vonschultzvonschultz
authored
docs/refactor: Use python.defaults, not is_default (bazel-contrib#2924)
When there are multiple Python toolchains, there are currently two ways of setting the default version: the `is_default` attribute of the `python.toolchain()` tag class and the `python.defaults()` tag class. The latter is more powerful, since it also supports files and environment variables. This patch updates the examples and the docs to use `python.defaults()`. Relates to pull request bazel-contrib#2588 and issue bazel-contrib#2587.
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‎docs/api/rules_python/python/bin/index.md

Copy file name to clipboardExpand all lines: docs/api/rules_python/python/bin/index.md
+2-1Lines changed: 2 additions & 1 deletion
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@@ -10,7 +10,8 @@
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A target to directly run a Python interpreter.
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By default, it uses the Python version that toolchain resolution matches
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(typically the one marked `is_default=True` in `MODULE.bazel`).
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(typically the one set with `python.defaults(python_version = ...)` in
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`MODULE.bazel`).
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This runs a Python interpreter in a similar manner as when running `python3`
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on the command line. It can be invoked using `bazel run`. Remember that in

‎docs/toolchains.md

Copy file name to clipboardExpand all lines: docs/toolchains.md
+11-4Lines changed: 11 additions & 4 deletions
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@@ -44,7 +44,8 @@ you should read the dev-only library module section.
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bazel_dep(name="rules_python", version=...)
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.toolchain(python_version = "3.12", is_default = True)
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python.defaults(python_version = "3.12")
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python.toolchain(python_version = "3.12")
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```
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### Library modules
@@ -72,7 +73,8 @@ python = use_extension(
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dev_dependency = True
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)
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python.toolchain(python_version = "3.12", is_default=True)
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python.defaults(python_version = "3.12")
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python.toolchain(python_version = "3.12")
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```
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#### Library modules without version constraints
@@ -161,9 +163,13 @@ Multiple versions can be specified and used within a single build.
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# MODULE.bazel
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.defaults(
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# The environment variable takes precedence if set.
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python_version = "3.11",
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python_version_env = "BAZEL_PYTHON_VERSION",
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)
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python.toolchain(
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python_version = "3.11",
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is_default = True,
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)
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python.toolchain(
@@ -264,7 +270,8 @@ bazel_dep(name = "rules_python", version = "0.40.0")
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.toolchain(is_default = True, python_version = "3.10")
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python.defaults(python_version = "3.10")
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python.toolchain(python_version = "3.10")
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use_repo(python, "python_3_10", "python_3_10_host")
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```

‎examples/bzlmod/MODULE.bazel

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+5-2Lines changed: 5 additions & 2 deletions
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@@ -28,10 +28,13 @@ bazel_dep(name = "rules_rust", version = "0.54.1")
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# We next initialize the python toolchain using the extension.
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# You can set different Python versions in this block.
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.defaults(
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# Use python.defaults if you have defined multiple toolchain versions.
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python_version = "3.9",
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python_version_env = "BAZEL_PYTHON_VERSION",
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)
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python.toolchain(
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configure_coverage_tool = True,
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# Only set when you have multiple toolchain versions.
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is_default = True,
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python_version = "3.9",
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)
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‎examples/bzlmod/other_module/MODULE.bazel

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+4-2Lines changed: 4 additions & 2 deletions
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@@ -25,14 +25,16 @@ PYTHON_NAME_39 = "python_3_9"
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PYTHON_NAME_311 = "python_3_11"
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.defaults(
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# In a submodule this is ignored
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python_version = "3.11",
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)
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python.toolchain(
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configure_coverage_tool = True,
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python_version = "3.9",
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)
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python.toolchain(
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configure_coverage_tool = True,
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# In a submodule this is ignored
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is_default = True,
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python_version = "3.11",
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)
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‎examples/bzlmod_build_file_generation/MODULE.bazel

Copy file name to clipboardExpand all lines: examples/bzlmod_build_file_generation/MODULE.bazel
+5-1Lines changed: 5 additions & 1 deletion
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@@ -46,9 +46,13 @@ python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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# We next initialize the python toolchain using the extension.
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# You can set different Python versions in this block.
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python.defaults(
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# The environment variable takes precedence if set.
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python_version = "3.9",
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python_version_env = "BAZEL_PYTHON_VERSION",
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)
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python.toolchain(
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configure_coverage_tool = True,
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is_default = True,
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python_version = "3.9",
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)
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‎examples/multi_python_versions/MODULE.bazel

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@@ -17,8 +17,6 @@ python.defaults(
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)
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python.toolchain(
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configure_coverage_tool = True,
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# Only set when you have mulitple toolchain versions.
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is_default = True,
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python_version = "3.9",
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)
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python.toolchain(

‎python/extensions/python.bzl

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+2-4Lines changed: 2 additions & 4 deletions
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@@ -20,10 +20,8 @@ The simplest way to configure the toolchain with `rules_python` is as follows.
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```starlark
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.toolchain(
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is_default = True,
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python_version = "3.11",
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)
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python.defaults(python_version = "3.11")
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python.toolchain(python_version = "3.11")
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use_repo(python, "python_3_11")
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```
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‎python/private/python.bzl

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+4-6Lines changed: 4 additions & 6 deletions
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@@ -223,7 +223,7 @@ def parse_modules(*, module_ctx, _fail = fail):
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# A default toolchain is required so that the non-version-specific rules
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# are able to match a toolchain.
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if default_toolchain == None:
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fail("No default Python toolchain configured. Is rules_python missing `is_default=True`?")
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fail("No default Python toolchain configured. Is rules_python missing `python.defaults()`?")
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elif default_toolchain.python_version not in global_toolchain_versions:
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fail('Default version "{python_version}" selected by module ' +
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'"{module_name}", but no toolchain with that version registered'.format(
@@ -891,10 +891,8 @@ In order to use a different name than the above, you can use the following `MODU
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syntax:
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```starlark
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python = use_extension("@rules_python//python/extensions:python.bzl", "python")
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python.toolchain(
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is_default = True,
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python_version = "3.11",
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)
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python.defaults(python_version = "3.11")
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python.toolchain(python_version = "3.11")
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use_repo(python, my_python_name = "python_3_11")
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```
@@ -930,7 +928,7 @@ Whether the toolchain is the default version.
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:::{versionchanged} 1.4.0
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This setting is ignored if the default version is set using the `defaults`
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tag class.
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tag class (encouraged).
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:::
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""",
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),

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