Jonathan Hourany created BEAM-12914:
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Summary: Trivial Type Inference Fails On 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
The [Build List
Unpack|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L39]
and [Build Tuple
Unapck|https://github.com/apache/beam/blob/8072cc0bcfd4eee08a95902e13b9bf1dc2338693/sdks/python/apache_beam/typehints/trivial_inference_test.py#L45]
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.
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