[lachlangrose]

Summary

The workflow packages.yml ran every package test job, map2loop and the root suite whenever anything under packages/ changed. A change in one package paid for all of them: about 15 minutes for the root suite on three Python versions and several operating systems.

A new changes job now decides which jobs run. On a pull request, a change runs its own tests and the tests of the code that depends on it:

Changed code	Tests that run
packages/loop_common	loop_common, loop_interpolation, visualisation, root suite
packages/loop_interpolation	loop_interpolation, visualisation, root suite
LoopStructural/, tests/, pyproject.toml	root suite, visualisation
packages/loopstructural_visualisation	visualisation
packages/map2loop	map2loop
uv.lock, .github/workflows/packages.yml	everything

This follows the dependencies in the pyproject.toml files: loop-interpolation needs loop-common, the root package needs both, loopstructuralvisualisation needs LoopStructural, and map2loop needs none of them.

A push to master and a manual run still run everything.

Details

• The changes job uses dorny/paths-filter@v3. It outputs the list of packages for the packages-test matrix, a flag for map2loop-test and a flag for the root suite. The decision is a short bash step in the workflow.
• packages-test and map2loop-test are skipped when they are not needed. The root suite uses always() so that a skipped job in needs does not skip it. It still stops if a job it waits for failed or was cancelled.
• The workflow now also triggers on changes in LoopStructural/**, tests/**, pyproject.toml and uv.lock. Before, a pull request that changed only the root package did not start this workflow at all. This is a change in coverage: those pull requests now run the root suite with uv, as the package pull requests already did. tester.yml is not changed.
• A skipped job shows as skipped, not failed. If a branch protection rule requires one of these checks, a skipped check counts as passed.

Test plan

• The workflow file parses as YAML, and the job dependencies are as intended.
• The selection step was run locally for nine cases (only map2loop, only loop_common, only loop_interpolation, only visualisation, only the root package, uv.lock or the workflow, nothing relevant, a push, a manual run). Each gave the table above, and the package list was valid JSON in each case.
• This pull request changes packages.yml, so it runs everything. It does not show the filtering. The first pull request after it merges shows the filtering. A pull request that touches only one package is a good check.
• GitHub Actions cannot run locally. The only part that I could not test is the dorny/paths-filter step and the if expression with always().