[JakeStevens]

Summary

Stacked on #24799. Until that lands this branch also contains its commits; review only the last commit, 121f6d6.

exir/backend/backend_api.py imports executorch.exir.program._fake_program, which runs exir/program/__init__.py and so _program.py. _program.py imported MethodProgramsPartitionerSpec and to_backend from the still half-initialised backend_api at module scope:

ImportError: cannot import name 'MethodProgramsPartitionerSpec' from partially initialized module 'executorch.exir.backend.backend_api' (most likely due to a circular import)

Normally exir/__init__.py loads program first, so this only fails when backend_api is the first executorch.exir import, for example under lazy imports (Cinder lazy imports on Python 3.14) when a backend imports to_backend directly. On main, that import order fails earlier on the capture cycle fixed in #24799, which is why this is stacked.

_program.py uses those two names only in EdgeProgramManager.to_backend, so the import moves into that method. Nothing imports them through _program.

This PR was authored with AI assistance (Claude Code).

Test plan

Added executorch.exir.backend.backend_api to exir/tests/test_import_order.py (added in #24799). It fails with the error above without the _program.py change and passes with it. The other entry points in that test still pass.

python -m unittest executorch.exir.program.test.test_program executorch.exir.backend.test.test_backends_lifted executorch.exir.backend.test.test_partitioner executorch.backends.xnnpack.test.ops.test_add gives the same results with and without this commit, apart from the new import-order case. The shared failures come from my local runtime build, which lacks BackendWithCompilerDemo and some kernels such as aten::_embedding_bag.out.

[pytorch-bot]

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[JakeStevens]

@claude review effort=max

[claude]

Claude finished @JakeStevens's task in 23m 7s —— View job

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The fix works for the backend_api-first import order, but its regression case goes into test_verifier.py, which pytest.ini excludes from OSS CI, and the PR description doesn't mention that import executorch.exir no longer loads backend_api.

Detailed review

PR Review: #24802

Summary

a23d2ca moves _program.py's import of MethodProgramsPartitionerSpec and to_backend into EdgeProgramManager.to_backend, so executorch.exir.backend.backend_api can be the first executorch.exir module imported. I found two problems:

• OSS CI never runs the new regression case.
• import executorch.exir no longer loads backend_api, and the description doesn't mention it.

I reviewed only a23d2ca, as you asked. This job isn't allowed to run Python, so I didn't run any tests. Everything below comes from reading the code.

Testing

• exir/verification/test/test_verifier.py:46: OSS CI never runs the new backend_api case.

  • pytest.ini:52 has --ignore=exir/verification/test/test_verifier.py, and no file under .ci/ or .github/ mentions it.
  • The only runner is the fbcode-only python_unittest(name = "test_verifier") in exir/verification/targets.bzl:62-71.
  • A normal import runs exir/__init__.py first, so program always loads before backend_api. If someone puts a module-scope backend_api import back into _program.py, every OSS test that does run still passes.
  • The placement comes from Break the exir capture <-> program/verifier import cycle #24799, so the fix belongs there:
    • Move TestImportOrder and _IMPORT_WITHOUT_EXIR_INIT into their own file that pytest collects, e.g. exir/tests/test_import_order.py.
    • Give that file a target that depends directly on each module the test imports. Today test_verifier only gets backend_api through other deps.
  • Low confidence: the child process is a bare sys.executable -c that doesn't get the parent's sys.path (test_verifier.py:49-54). Under a Buck PAR it may not find executorch at all. Worth confirming that the fbcode target actually passes.

  Fix this →

Backward Compatibility

• exir/program/_program.py:1724-1729: import executorch.exir no longer loads executorch.exir.backend.backend_api.
  • _program.py was the only non-test module in exir/ that imported backend_api, and exir/backend/ has no __init__.py.
  • So code that does import executorch.exir and then uses executorch.exir.backend.backend_api.<name> without importing that module now gets AttributeError.
  • I found no such use in the repo, so the out-of-tree impact is probably small. The description's "Nothing imports them through _program" covers the two names, not this. One sentence in the description would cover it.
  • There is a way to keep the old behaviour. Keep _program.py's module-scope import, and move the _fake_program import at exir/backend/backend_api.py:35-38 into the two overloads that use it (backend_api.py:367 and :684). That's the kind of fix Break the exir capture <-> program/verifier import cycle #24799 moved away from (01c8118 → 3f8c4fb), though, so documenting the change may be the better option.

Specific Comments

• exir/program/_program.py:1724-1725:
  • The "it" in "importing it at module scope is circular" is ambiguous.
  • This file already words cycle comments differently, at _program.py:241 ("program -> etrecord -> program").
  • Suggested wording: # Import at runtime to resolve cyclic dependencies (backend_api -> program._fake_program -> program/__init__ -> _program -> backend_api).

Recommendation

Approve

Nothing in a23d2ca blocks this. The Testing item still needs fixing in #24799 before the stack lands. Until then, the fix has no regression test in OSS CI.