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https://issues.apache.org/jira/browse/BEAM-12914?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Hourany updated BEAM-12914:
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Summary: Trivial Type Inference Fails On Lambda Functions in Python 3.9
(was: Trivial Type Inference Fails On Functions in Python 3.9)
> Trivial Type Inference Fails On Lambda Functions in Python 3.9
> --------------------------------------------------------------
>
> Key: BEAM-12914
> URL: https://issues.apache.org/jira/browse/BEAM-12914
> Project: Beam
> Issue Type: Bug
> Components: test-failures
> Affects Versions: 2.32.0
> Environment: Python 3.9.7
> Linux Mint 20.2, Kernel: 5.4.0-84-generic
> Reporter: Jonathan Hourany
> Priority: P2
>
> The [Build List
> Unpack,|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L39]
> [Build Tuple
> Unapck|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L45],
> and [Build Tuple Unpack With
> Call|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L305]
> tests in [Trivial Inference
> Test|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L33]
> fail in Python 3.9 because the opcodes lambda functions use in Python 3.9
> have changed.
> {code:python}
> # Python3.7
> In [1]: from dis import dis
> In [2]: from apache_beam.typehints import typehints
> In [3]: beam_type_hints = [typehints.List[int]]
> In [4]: dis(lambda _list: [*_list, *_list, *_list](beam_type_hints))
> 1 0 LOAD_FAST 0 (_list)
> 2 LOAD_FAST 0 (_list)
> 4 LOAD_FAST 0 (_list)
> 6 BUILD_LIST_UNPACK 3
> 8 LOAD_GLOBAL 0 (beam_type_hints)
> 10 CALL_FUNCTION 1
> 12 RETURN_VALUE
> {code}
> ----
> Whereas in Python 3.9
> {code:python}
> # Python 3.9
> In [1]: from dis import dis
> In [2]: from apache_beam.typehints import typehints
> In [3]: beam_type_hints = [typehints.List[int]]
> In [4]: dis(lambda _list: [*_list, *_list, *_list](beam_type_hints))
> <>:1: SyntaxWarning: 'list' object is not callable; perhaps you missed a
> comma?
> <ipython-input-4-6499114c3d61>:1: SyntaxWarning: 'list' object is not
> callable; perhaps you missed a comma?
> dis(lambda _list: [*_list, *_list, *_list](beam_type_hints))
> 1 0 BUILD_LIST 0
> 2 LOAD_FAST 0 (_list)
> 4 LIST_EXTEND 1
> 6 LOAD_FAST 0 (_list)
> 8 LIST_EXTEND 1
> 10 LOAD_FAST 0 (_list)
> 12 LIST_EXTEND 1
> 14 LOAD_GLOBAL 0 (beam_type_hints)
> 16 CALL_FUNCTION 1
> 18 RETURN_VALUE
> {code}
> The `SyntaxWarning` is most likely raising because enhancment in
> [bpo-15248|https://bugs.python.org/issue15248] misses the fact that the
> lambda expression is a function, not a list we're calling, and isn't relevant
> to the issue.
>
> This causes type inference to return `Any` instead of the proper type as
> shown by the test failures
> {code}
> ./sdks/python/apache_beam/typehints/trivial_inference_test.py::TrivialInferenceTest::testBuildListUnpack
> Failed: [undefined]AssertionError: List[int] != Any
> {code}
>
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