[moneebullah25]

Description

MigrationGraph.leaf_nodes(app_label) and root_nodes(app_label) now ignore edges to or from other apps when an app_label is given. Both methods share one helper. Calls without app_label behave as before.

Motivation and Context

When app B depends on the newest migration of app A, that migration has a child in app B, so leaf_nodes("A") returned nothing. Targets like A.__latest__ (and A.__first__ in the mirrored case) then failed to resolve.

Fixes #2305

How Has This Been Tested?

• Added test_graph_leaf_and_root_nodes_ignore_cross_app_edges (graph level).
• Added test_loader_resolves_cross_app_latest_and_first (loader resolving __latest__ / __first__ across apps).
• Ran python -m pytest tests/migrations/test_runtime_migrations.py -q: 15 passed.
• With graph.py swapped for the develop version, the new graph test fails, so it covers the bug.
• Ran ruff check, ruff format --check and codespell on the changed files: pass. The local ruff is 0.15.4 and the pin is 0.15.9.

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing moneebullah25:fix/migration-graph-leaf-root-cross-app (052b070) with develop (5815573)}

[moneebullah25]

Closing this as a duplicate of #2307, which was opened first for the same issue.