swev-id: matplotlib__matplotlib-26342 feat: add ContourSet.set_paths

[casey-brooks]

Summary

• add ContourSet.set_paths with validation, cache invalidation, and stale updates
• declare the typing stub for the new setter
• expand contour tests to cover path replacement, transformed labeling, and unchanged defaults

Testing

• MPLBACKEND=Agg PYTHONPATH=/workspace/matplotlib/lib LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib .venv/bin/pytest lib/matplotlib/tests/test_contour_set_paths.py -n 0
• .venv/bin/flake8 lib/matplotlib/contour.py lib/matplotlib/tests/test_contour_set_paths.py
• MPLBACKEND=Agg PYTHONPATH=/workspace/matplotlib/lib LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib .venv/bin/pytest lib/matplotlib/tests/test_contour.py -k contour -n 0 (fails: MatplotlibDeprecationWarning emitted where PendingDeprecationWarning expected in test_deprecated_apis)

Closes #71

[casey-brooks]

Test & Lint Summary

• .venv/bin/flake8 lib/matplotlib/contour.py lib/matplotlib/tests/test_contour_set_paths.py (pass: no findings)
• MPLBACKEND=Agg PYTHONPATH=/workspace/matplotlib/lib LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib .venv/bin/pytest lib/matplotlib/tests/test_contour_set_paths.py -n 0 (pass: 3 passed, 0 failed)
• MPLBACKEND=Agg PYTHONPATH=/workspace/matplotlib/lib LD_LIBRARY_PATH=/root/.nix-profile/lib:/nix/store/qipd93x9gjyiygqk673rd2ssnf8y7jj0-gcc-14.3.0-lib/lib:/nix/store/f8w1i7yisixb9hivzbk0l4ixmf67fjqr-gcc-14.3.0-libgcc/lib .venv/bin/pytest lib/matplotlib/tests/test_contour.py -k contour -n 0 (fails on baseline: MatplotlibDeprecationWarning raised where PendingDeprecationWarning expected in test_deprecated_apis)

[noa-lucent]

Thanks for wiring up and the accompanying tests. I left one major comment: after replacing the paths we still leave , , and the axes' cached limits pointing at the previous geometry. That keeps the ContourSet metadata inconsistent (autoscale, sticky edges, etc.). Please recompute the bounds from the new paths and update the cached limits so the setter keeps the object self-consistent.

[noa-lucent]

Re-ran the contour-set review: the new implementation now recomputes /, refreshes the sticky edges, and updates the axes’ data limits after swapping paths. The regression test also verifies that moves when the geometry shifts. Looks good to me.