Fix type annotation for plt.subplot_mosaic #29893

gshiba · Apr 9, 2025

PR summary

Fixes the following type error:

# foo.py
import matplotlib.pyplot as plt
mosaic = [["a"], ["b"]]
fig, axes = plt.subplot_mosaic(mosaic)

$ mypy foo.py 
foo.py:3: error: Argument 1 to "subplot_mosaic" has incompatible type "list[list[str]]"; expected "Sequence[HashableList[str]]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

$ pyright foo.py
 * Install prebuilt node (23.11.0) ..... done.
/home/ec2-user/repos/repro-mpl/foo.py
  /home/ec2-user/repos/repro-mpl/foo.py:3:13 - error: No overloads for "subplot_mosaic" match the provided arguments (reportCallIssue)
  /home/ec2-user/repos/repro-mpl/foo.py:3:32 - error: Argument of type "list[list[str]]" cannot be assigned to parameter "mosaic" of type "Sequence[HashableList[Hashable]]" in function "subplot_mosaic"
    "list[list[str]]" is not assignable to "Sequence[HashableList[Hashable]]"
      Type parameter "_T_co@Sequence" is covariant, but "list[str]" is not a subtype of "HashableList[Hashable]"
        "list[str]" is not assignable to "list[Hashable | HashableList]"
          Type parameter "_T@list" is invariant, but "str" is not the same as "Hashable | HashableList"
          Consider switching from "list" to "Sequence" which is covariant (reportArgumentType)
2 errors, 0 warnings, 0 informations

PR checklist

"closes #0000" is in the body of the PR description to link the related issue
new and changed code is tested
Plotting related features are demonstrated in an example
New Features and API Changes are noted with a directive and release note
Documentation complies with general and docstring guidelines

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timhoffm · Apr 9, 2025

What is The reason for this change? Do you have any particular use case? At least when writing out the spec explicitly, I'd want users to use lists. I rather consider the general support of sequences an implementation detail.

gshiba · Apr 9, 2025

Set up:

repos/repro-mpl$ python -m venv venv                                                                                                                                                     
repos/repro-mpl$ . venv/bin/activate  
(venv) repos/repro-mpl$ pip install mypy matplotlib 
(venv) repos/repro-mpl$ mypy --version
mypy 1.15.0 (compiled: yes)
(venv) repos/repro-mpl$ python -c 'import matplotlib; print(matplotlib.__version__)'
3.10.1
(venv) repos/repro-mpl$ python --version
Python 3.10.16

This is what I was trying to solve:

(venv) repos/repro-mpl$ cat foo.py
import matplotlib.pyplot as plt
mosaic = [["a"], ["b"]]
fig, axes = plt.subplot_mosaic(mosaic)

(venv) repos/repro-mpl$ mypy foo.py 
foo.py:3: error: Argument 1 to "subplot_mosaic" has incompatible type "list[list[str]]"; expected "Sequence[HashableList[str]]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

Evidently, this PR as of 4b7038d does not fix this yet...

Edit: here's pyright's error message:

(venv) repos/repro-mpl$ pyright foo.py
 * Install prebuilt node (23.11.0) ..... done.
/home/ec2-user/repos/repro-mpl/foo.py
  /home/ec2-user/repos/repro-mpl/foo.py:3:13 - error: No overloads for "subplot_mosaic" match the provided arguments (reportCallIssue)
  /home/ec2-user/repos/repro-mpl/foo.py:3:32 - error: Argument of type "list[list[str]]" cannot be assigned to parameter "mosaic" of type "Sequence[HashableList[Hashable]]" in function "subplot_mosaic"
    "list[list[str]]" is not assignable to "Sequence[HashableList[Hashable]]"
      Type parameter "_T_co@Sequence" is covariant, but "list[str]" is not a subtype of "HashableList[Hashable]"
        "list[str]" is not assignable to "list[Hashable | HashableList]"
          Type parameter "_T@list" is invariant, but "str" is not the same as "Hashable | HashableList"
          Consider switching from "list" to "Sequence" which is covariant (reportArgumentType)
2 errors, 0 warnings, 0 informations

gshiba · Apr 9, 2025

With b743a81

(venv) repos/repro-mpl$ mypy foo.py 
Success: no issues found in 1 source file
(venv) repos/repro-mpl$ pyright foo.py 
0 errors, 0 warnings, 0 informations

With the changes in b743a81, pyright says there are 3 fewer errors than before (7386 vs 7389)

$ pyright venv/lib/python3.10/site-packages/matplotlib
7386 errors, 33 warnings, 0 informations

How can/should I test the implication of this change on the rest of repo? I was not able to set up a dev env, even in CodeSpaces. Happy to try again...

timhoffm · Apr 9, 2025

Ok thanks for the clarification. I suspect that you're barking up the wrong tree and instead the TypeVar _HT used in HashableList might need to be declared covariant. But I'm not that much in to typing maybe @QuLogic can help here.

As for the dev setup, the description is here: https://matplotlib.org/devdocs/devel/development_setup.html Have you tried to follow that?

gshiba · Apr 10, 2025

Yes, I followed it but can't get an editable install.

After clicking on the "Create codespace" button and waiting a few minutes, here's what I get in the Terminal:

(base) @gshiba ➜ /workspaces/matplotlib (main) $ conda activate mpl-dev
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -c 'import matplotlib; print(matplotlib.__file__)'
/home/codespace/.local/lib/python3.12/site-packages/matplotlib/__init__.py
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -m pip install --verbose --no-build-isolation --editable ".[dev]"
...
ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
seaborn 0.13.2 requires matplotlib!=3.6.1,>=3.4, but you have matplotlib 0.1.0.dev52310+g7e997ae which is incompatible.
Successfully installed matplotlib-0.1.0.dev52310+g7e997ae meson-python-0.16.0
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -c 'import matplotlib; print(matplotlib.__file__)'
Traceback (most recent call last):
...
ImportError: /workspaces/matplotlib/build/cp312/src/_path.cpython-312-x86_64-linux-gnu.so: undefined symbol: _ZN3agg10curve3_div4initEdddddd

Full traceback

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📝 Edit away, run your app as usual, and we'll automatically make it available for you to access.

(base) @gshiba ➜ /workspaces/matplotlib (main) $ conda activate mpl-dev
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -c 'import matplotlib; print(matplotlib.__file__)'
/home/codespace/.local/lib/python3.12/site-packages/matplotlib/__init__.py
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -m pip install --verbose --no-build-isolation --editable ".[dev]"
Using pip 25.0.1 from /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages/pip (python 3.12)
Obtaining file:///workspaces/matplotlib
  Running command Checking if build backend supports build_editable
  Checking if build backend supports build_editable ... done
  Running command Preparing editable metadata (pyproject.toml)
  + meson setup /workspaces/matplotlib /workspaces/matplotlib/build/cp312 -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --native-file=/workspaces/matplotlib/build/cp312/meson-python-native-file.ini
  The Meson build system
  Version: 1.7.1
  Source dir: /workspaces/matplotlib
  Build dir: /workspaces/matplotlib/build/cp312
  Build type: native build
  Program python3 found: YES (/home/codespace/micromamba/envs/mpl-dev/bin/python3)
  Project name: matplotlib
  Project version: 0.1.0.dev52310+g7e997ae
  C compiler for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc (gcc 13.3.0 "x86_64-conda-linux-gnu-cc (conda-forge gcc 13.3.0-2) 13.3.0")
  C linker for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc ld.bfd 2.43
  C++ compiler for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-c++ (gcc 13.3.0 "x86_64-conda-linux-gnu-c++ (conda-forge gcc 13.3.0-2) 13.3.0")
  C++ linker for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-c++ ld.bfd 2.43
  Host machine cpu family: x86_64
  Host machine cpu: x86_64
  Program python found: YES (/home/codespace/micromamba/envs/mpl-dev/bin/python)
  Found pkg-config: YES (/home/codespace/micromamba/envs/mpl-dev/bin/pkg-config) 0.29.2
  Run-time dependency python found: YES 3.12
  Run-time dependency pybind11 found: YES 2.13.6
  Downloading freetype-2.6.1 source from https://download.savannah.gnu.org/releases/freetype/freetype-old/freetype-2.6.1.tar.gz

  Executing subproject freetype-2.6.1

  freetype-2.6.1| Project name: freetype2
  freetype-2.6.1| Project version: 2.6.1
  freetype-2.6.1| C compiler for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc (gcc 13.3.0 "x86_64-conda-linux-gnu-cc (conda-forge gcc 13.3.0-2) 13.3.0")
  freetype-2.6.1| C linker for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc ld.bfd 2.43
  freetype-2.6.1| Has header "unistd.h" : YES
  freetype-2.6.1| Has header "fcntl.h" : YES
  freetype-2.6.1| Has header "stdint.h" : YES
  freetype-2.6.1| Configuring ftconfig.h using configuration
  freetype-2.6.1| Configuring ftoption.h using configuration
  freetype-2.6.1| Build targets in project: 2
  freetype-2.6.1| Subproject freetype-2.6.1 finished.

  Downloading qhull source from https://github.com/qhull/qhull/archive/v8.0.2/qhull-8.0.2.tar.gz

  Executing subproject qhull

  qhull| Project name: qhull
  qhull| Project version: 8.0.2
  qhull| C compiler for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc (gcc 13.3.0 "x86_64-conda-linux-gnu-cc (conda-forge gcc 13.3.0-2) 13.3.0")
  qhull| C linker for the host machine: /home/codespace/micromamba/envs/mpl-dev/bin/x86_64-conda-linux-gnu-cc ld.bfd 2.43
  qhull| Build targets in project: 3
  qhull| Subproject qhull finished.

  Run-time dependency dl found: YES
  Configuring _version.py using configuration
  Program /workspaces/matplotlib/tools/generate_matplotlibrc.py found: YES (/workspaces/matplotlib/tools/generate_matplotlibrc.py)
  Build targets in project: 12

  matplotlib 0.1.0.dev52310+g7e997ae

    Subprojects
      freetype-2.6.1: YES
      qhull         : YES

    User defined options
      Native files  : /workspaces/matplotlib/build/cp312/meson-python-native-file.ini
      b_ndebug      : if-release
      b_vscrt       : md
      buildtype     : release

  Found ninja-1.12.1 at /home/codespace/micromamba/envs/mpl-dev/bin/ninja
  + /home/codespace/micromamba/envs/mpl-dev/bin/ninja
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  [55/91] Compiling C object subprojects/freetype-2.6.1/libfreetype.a.p/src_truetype_truetype.c.o
  In file included from ../../subprojects/freetype-2.6.1/src/truetype/truetype.c:25:
  ../../subprojects/freetype-2.6.1/src/truetype/ttgload.c: In function 'load_truetype_glyph':
  ../../subprojects/freetype-2.6.1/src/truetype/ttgload.c:1455:22: warning: storing the address of local variable 'inc_stream' in 'loader_405(D)->stream' [-Wdangling-pointer=]
   1455 |       loader->stream = &inc_stream;
        |       ~~~~~~~~~~~~~~~^~~~~~~~~~~~~
  ../../subprojects/freetype-2.6.1/src/truetype/ttgload.c:1392:21: note: 'inc_stream' declared here
   1392 |     FT_StreamRec    inc_stream;
        |                     ^~~~~~~~~~
  ../../subprojects/freetype-2.6.1/src/truetype/ttgload.c:1379:35: note: 'loader' declared here
   1379 |   load_truetype_glyph( TT_Loader  loader,
        |                        ~~~~~~~~~~~^~~~~~
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  [80/91] Compiling C++ object src/_path.cpython-312-x86_64-linux-gnu.so.p/_path_wrapper.cpp.o
  [81/91] Linking target src/_c_internal_utils.cpython-312-x86_64-linux-gnu.so
  [82/91] Compiling C++ object src/_tri.cpython-312-x86_64-linux-gnu.so.p/tri__tri.cpp.o
  [83/91] Linking target src/_backend_agg.cpython-312-x86_64-linux-gnu.so
  [84/91] Compiling C++ object src/_tri.cpython-312-x86_64-linux-gnu.so.p/tri__tri_wrapper.cpp.o
  [85/91] Linking target src/ft2font.cpython-312-x86_64-linux-gnu.so
  [86/91] Generating lib/matplotlib/mpl-data/matplotlibrc with a custom command
  [87/91] Linking target src/_path.cpython-312-x86_64-linux-gnu.so
  [88/91] Linking target src/_image.cpython-312-x86_64-linux-gnu.so
  [89/91] Linking target src/_qhull.cpython-312-x86_64-linux-gnu.so
  [90/91] Linking target src/_tkagg.cpython-312-x86_64-linux-gnu.so
  [91/91] Linking target src/_tri.cpython-312-x86_64-linux-gnu.so
  Preparing editable metadata (pyproject.toml) ... done
Requirement already satisfied: contourpy>=1.0.1 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (1.3.1)
Requirement already satisfied: cycler>=0.10 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (0.12.1)
Requirement already satisfied: fonttools>=4.22.0 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (4.56.0)
Requirement already satisfied: kiwisolver>=1.3.1 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (1.4.8)
Requirement already satisfied: numpy>=1.23 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (2.2.4)
Requirement already satisfied: packaging>=20.0 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (24.2)
Requirement already satisfied: pillow>=9 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (11.1.0)
Requirement already satisfied: pyparsing>=2.3.1 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (3.2.1)
Requirement already satisfied: python-dateutil>=2.7 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (2.9.0.post0)
Collecting meson-python<0.17.0,>=0.13.1 (from matplotlib==0.1.0.dev52310+g7e997ae)
  Obtaining dependency information for meson-python<0.17.0,>=0.13.1 from https://files.pythonhosted.org/packages/91/c0/104cb6244c83fe6bc3886f144cc433db0c0c78efac5dc00e409a5a08c87d/meson_python-0.16.0-py3-none-any.whl.metadata
  Downloading meson_python-0.16.0-py3-none-any.whl.metadata (4.1 kB)
Requirement already satisfied: pybind11!=2.13.3,>=2.13.2 in /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (2.13.6)
Requirement already satisfied: setuptools_scm>=7 in /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (8.2.1)
Requirement already satisfied: setuptools>=64 in /home/codespace/.local/lib/python3.12/site-packages (from matplotlib==0.1.0.dev52310+g7e997ae) (76.0.0)
Requirement already satisfied: meson>=1.2.3 in /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages (from meson-python<0.17.0,>=0.13.1->matplotlib==0.1.0.dev52310+g7e997ae) (1.7.1)
Requirement already satisfied: pyproject-metadata>=0.7.1 in /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages (from meson-python<0.17.0,>=0.13.1->matplotlib==0.1.0.dev52310+g7e997ae) (0.9.1)
Requirement already satisfied: six>=1.5 in /home/codespace/.local/lib/python3.12/site-packages (from python-dateutil>=2.7->matplotlib==0.1.0.dev52310+g7e997ae) (1.17.0)
Downloading meson_python-0.16.0-py3-none-any.whl (26 kB)
Building wheels for collected packages: matplotlib
  Running command Building editable for matplotlib (pyproject.toml)
  Building editable for matplotlib (pyproject.toml) ... done
  Created wheel for matplotlib: filename=matplotlib-0.1.0.dev52310+g7e997ae-cp312-cp312-linux_x86_64.whl size=10377 sha256=aaead17634334704f01882f8294695fe6ea741b5b35982fe4fe66407d613bde5
  Stored in directory: /tmp/pip-ephem-wheel-cache-w5zz02zy/wheels/12/a2/a8/efadc28c14fa1750547f26b6cb4f3e357cd1fa0797dc7e1949
Successfully built matplotlib
Installing collected packages: meson-python, matplotlib
  Attempting uninstall: meson-python
    Found existing installation: meson-python 0.17.1
    Uninstalling meson-python-0.17.1:
      Removing file or directory /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages/meson_python-0.17.1.dist-info/
      Removing file or directory /home/codespace/micromamba/envs/mpl-dev/lib/python3.12/site-packages/mesonpy/
      Successfully uninstalled meson-python-0.17.1
  Attempting uninstall: matplotlib
    Found existing installation: matplotlib 3.10.1
    Uninstalling matplotlib-3.10.1:
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/__pycache__/pylab.cpython-312.pyc
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/matplotlib-3.10.1.dist-info/
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/matplotlib/
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/mpl_toolkits/axes_grid1/
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/mpl_toolkits/axisartist/
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/mpl_toolkits/mplot3d/
      Removing file or directory /home/codespace/.local/lib/python3.12/site-packages/pylab.py
      Successfully uninstalled matplotlib-3.10.1
ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
seaborn 0.13.2 requires matplotlib!=3.6.1,>=3.4, but you have matplotlib 0.1.0.dev52310+g7e997ae which is incompatible.
Successfully installed matplotlib-0.1.0.dev52310+g7e997ae meson-python-0.16.0
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $ python -c 'import matplotlib; print(matplotlib.__file__)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/workspaces/matplotlib/lib/matplotlib/__init__.py", line 161, in <module>
    from . import _api, _version, cbook, _docstring, rcsetup
  File "/workspaces/matplotlib/lib/matplotlib/rcsetup.py", line 29, in <module>
    from matplotlib.colors import Colormap, is_color_like
  File "/workspaces/matplotlib/lib/matplotlib/colors.py", line 57, in <module>
    from matplotlib import _api, _cm, cbook, scale, _image
  File "/workspaces/matplotlib/lib/matplotlib/scale.py", line 39, in <module>
    from matplotlib.ticker import (
  File "/workspaces/matplotlib/lib/matplotlib/ticker.py", line 144, in <module>
    from matplotlib import transforms as mtransforms
  File "/workspaces/matplotlib/lib/matplotlib/transforms.py", line 49, in <module>
    from matplotlib._path import affine_transform, count_bboxes_overlapping_bbox
ImportError: /workspaces/matplotlib/build/cp312/src/_path.cpython-312-x86_64-linux-gnu.so: undefined symbol: _ZN3agg10curve3_div4initEdddddd
(mpl-dev) @gshiba ➜ /workspaces/matplotlib (main) $

... but this is off topic. Shall I create a separate issue for this?

timhoffm · Apr 10, 2025

Your setup is broken, the issue is hat you have stuff in /home/codespace/.local/lib/python3.12. This can e.g. happen if you have at some point installed something with pip install --user. Such installed packages are global for your user, i.e. included in every python 3.12 interperter you run. This breaks the separatation you get from environments. Generally you should not have anything in local/lib if you work with environements.

ksunden · Apr 10, 2025

In the general case, I would tend to agree that on parameters, using Sequence is often better than over-specifying as list. A general principle in typing is to be permissive on parameters and restrictive on returns where possible.

However, in this specific case, this parameter gets a little harder to deal with in particular because str counts as a Sequence, which complicates some things. Not necessarily impossible to overcome, but I'd want to think on it at least a bit more.

What I'm confused by, though, is in this example I think that the distinction between Sequence and list should be inconsequential, as list is being used... so I'm not clear why it is failing the type check to begin with.

QuLogic · Apr 10, 2025

Your setup is broken, the issue is hat you have stuff in /home/codespace/.local/lib/python3.12. This can e.g. happen if you have at some point installed something with pip install --user. Such installed packages are global for your user, i.e. included in every python 3.12 interperter you run. This breaks the separatation you get from environments. Generally you should not have anything in local/lib if you work with environements.

That is not the case here; it is a bug in our setup for conda, or conda-forge itself. Please see #29852.

gshiba · May 23, 2025

@ksunden

What I'm confused by, though, is in this example I think that the distinction between Sequence and list should be inconsequential, as list is being used... so I'm not clear why it is failing the type check to begin with.

The problem is in expected vs inferred type of the inner list:

the existing code expects the inner list to be: HashableList: TypeAlias = list[_HT | "HashableList[_HT]"]
the inferred type of [["a"], ["b"]] is list[list[str]] which means the inner list is strictly a list of _HT.

Demo:

# foo.py
import matplotlib.pyplot as plt

inferred_mosaic = [["a"], ["b"]]
reveal_type(inferred_mosaic)
fig, axes = plt.subplot_mosaic(inferred_mosaic)  # type error

explicit_mosaic: list[list[str | list]]  = [["a"], ["b"]]
reveal_type(explicit_mosaic)
fig, axes = plt.subplot_mosaic(explicit_mosaic)  # type ok

$ pyright foo.py
/Users/ec2-user/repos/matplotlib-test/foo.py
  /Users/ec2-user/repos/matplotlib-test/foo.py:5:13 - information: Type of "inferred_mosaic" is "list[list[str]]"
  /Users/ec2-user/repos/matplotlib-test/foo.py:6:13 - error: No overloads for "subplot_mosaic" match the provided arguments (reportCallIssue)
  /Users/ec2-user/repos/matplotlib-test/foo.py:6:32 - error: Argument of type "list[list[str]]" cannot be assigned to parameter "mosaic" of type "list[HashableList[Hashable]]" in function "subplot_mosaic"
    "list[list[str]]" is not assignable to "list[HashableList[Hashable]]"
      Type parameter "_T@list" is invariant, but "list[str]" is not the same as "HashableList[Hashable]"
      Consider switching from "list" to "Sequence" which is covariant (reportArgumentType)
  /Users/ec2-user/repos/matplotlib-test/foo.py:9:13 - information: Type of "explicit_mosaic" is "list[list[str | list[Unknown]]]"
2 errors, 0 warnings, 2 informations

... and this can be resolved by changing the type from list to Sequence (this PR) which makes the inner (and outer) list immutable.

s/list/Sequence/

4b7038d

github-actions bot added the topic: pyplot API label Apr 9, 2025

github-actions bot reviewed Apr 9, 2025

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fix

b743a81

gshiba marked this pull request as ready for review April 10, 2025 01:37

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Fix type annotation for plt.subplot_mosaic #29893

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