Handle empty bodies safely

[ilevkivskyi]

Fixes #2350

This essentially re-applies #8111 modulo various (logical) changes in master since then.The only important difference is that now I override few return-related error codes for empty bodies, to allow opting out easily in next few versions (I still keep the flag to simplify testing).

[hauntsaninja]

primer fallout seems really bad :-/ there's at least one fixable issue related to attrs, e.g. https://github.com/sco1/pylox/blob/393c029a8f503459e36367b990e43736f04bc5b9/pylox/tokens.py#L66

[ilevkivskyi]

So I fixed the the plugin generated methods (now they don't require a body), and also allowed empty bodies if the return type is Optional (or if --strict-optional is off) to minimize fallout. There are still ~110 new errors. I looked through them and they are all kind of real. OTOH this is expected, we didn't check empty bodies for really long time.

[JukkaL]

I think that it will be inevitable that this will generate some new errors, and it seems worth it since not having the checks has been a pretty big omission in mypy (of course assuming that they aren't false positives).

[JukkaL]

Looks great, just left some minor comments. This fixes a big safety hole in type checking. Thanks for carefully minimizing the fallout and false positives.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

ignite (https://github.com/pytorch/ignite)
+ ignite/contrib/handlers/tqdm_logger.py:226: error: Missing return statement  [empty-body]
+ ignite/contrib/handlers/tqdm_logger.py:226: note: If the method is meant to be abstract, use @abc.abstractmethod
+ ignite/contrib/handlers/tqdm_logger.py:235: error: Missing return statement  [empty-body]
+ ignite/contrib/handlers/tqdm_logger.py:235: note: If the method is meant to be abstract, use @abc.abstractmethod

artigraph (https://github.com/artigraph/artigraph)
+ tests/arti/producers/test_producer.py:34: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:34: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:34: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:38: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:38: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:104: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:104: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:104: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:118: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:118: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:118: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:129: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:129: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:129: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:143: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:143: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:143: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:155: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:155: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:155: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:170: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:170: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:170: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:181: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:181: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:181: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:191: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:191: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:191: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:253: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:253: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:253: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:257: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:257: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:269: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:269: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:269: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:371: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:371: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:376: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:376: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:376: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:388: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:388: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:388: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:398: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:398: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:398: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:421: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:421: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:421: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:431: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:431: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:431: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:435: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:435: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:448: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:448: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:448: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:466: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:466: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:554: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:554: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:554: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:566: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:566: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:566: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:573: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:573: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:585: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:585: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:594: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:594: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:594: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:604: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:604: note: Error code "empty-body" not covered by "type: ignore" comment
+ tests/arti/producers/test_producer.py:604: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:607: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:607: note: If the method is meant to be abstract, use @abc.abstractmethod
+ tests/arti/producers/test_producer.py:696: error: Missing return statement  [empty-body]
+ tests/arti/producers/test_producer.py:696: note: If the method is meant to be abstract, use @abc.abstractmethod

Expression (https://github.com/cognitedata/Expression)
+ expression/core/typing.py:67: error: Missing return statement  [empty-body]

prefect (https://github.com/PrefectHQ/prefect)
+ src/prefect/packaging/base.py:22: error: Missing return statement  [empty-body]
+ src/prefect/packaging/base.py:22: note: If the method is meant to be abstract, use @abc.abstractmethod
+ src/prefect/packaging/base.py:25: error: Missing return statement  [empty-body]
+ src/prefect/packaging/base.py:25: note: If the method is meant to be abstract, use @abc.abstractmethod

mypy (https://github.com/python/mypy)
+ mypy/visitor.py:363: error: Missing return statement  [empty-body]
+ mypy/visitor.py:369: error: Missing return statement  [empty-body]
+ mypy/visitor.py:374: error: Missing return statement  [empty-body]
+ mypy/visitor.py:377: error: Missing return statement  [empty-body]
+ mypy/visitor.py:380: error: Missing return statement  [empty-body]
+ mypy/visitor.py:385: error: Missing return statement  [empty-body]
+ mypy/visitor.py:388: error: Missing return statement  [empty-body]
+ mypy/visitor.py:391: error: Missing return statement  [empty-body]
+ mypy/visitor.py:394: error: Missing return statement  [empty-body]
+ mypy/visitor.py:397: error: Missing return statement  [empty-body]
+ mypy/visitor.py:400: error: Missing return statement  [empty-body]
+ mypy/visitor.py:403: error: Missing return statement  [empty-body]
+ mypy/visitor.py:406: error: Missing return statement  [empty-body]
+ mypy/visitor.py:411: error: Missing return statement  [empty-body]
+ mypy/visitor.py:414: error: Missing return statement  [empty-body]
+ mypy/visitor.py:417: error: Missing return statement  [empty-body]
+ mypy/visitor.py:420: error: Missing return statement  [empty-body]
+ mypy/visitor.py:423: error: Missing return statement  [empty-body]
+ mypy/visitor.py:426: error: Missing return statement  [empty-body]
+ mypy/visitor.py:429: error: Missing return statement  [empty-body]
+ mypy/visitor.py:432: error: Missing return statement  [empty-body]
+ mypy/visitor.py:435: error: Missing return statement  [empty-body]
+ mypy/visitor.py:438: error: Missing return statement  [empty-body]
+ mypy/visitor.py:441: error: Missing return statement  [empty-body]
+ mypy/visitor.py:444: error: Missing return statement  [empty-body]
+ mypy/visitor.py:447: error: Missing return statement  [empty-body]
+ mypy/visitor.py:450: error: Missing return statement  [empty-body]
+ mypy/visitor.py:453: error: Missing return statement  [empty-body]
+ mypy/visitor.py:456: error: Missing return statement  [empty-body]
+ mypy/visitor.py:459: error: Missing return statement  [empty-body]
+ mypy/visitor.py:464: error: Missing return statement  [empty-body]
+ mypy/visitor.py:467: error: Missing return statement  [empty-body]
+ mypy/visitor.py:470: error: Missing return statement  [empty-body]
+ mypy/visitor.py:473: error: Missing return statement  [empty-body]
+ mypy/visitor.py:476: error: Missing return statement  [empty-body]
+ mypy/visitor.py:479: error: Missing return statement  [empty-body]
+ mypy/visitor.py:482: error: Missing return statement  [empty-body]
+ mypy/visitor.py:485: error: Missing return statement  [empty-body]
+ mypy/visitor.py:488: error: Missing return statement  [empty-body]
+ mypy/visitor.py:491: error: Missing return statement  [empty-body]
+ mypy/visitor.py:494: error: Missing return statement  [empty-body]
+ mypy/visitor.py:497: error: Missing return statement  [empty-body]
+ mypy/visitor.py:500: error: Missing return statement  [empty-body]
+ mypy/visitor.py:503: error: Missing return statement  [empty-body]
+ mypy/visitor.py:506: error: Missing return statement  [empty-body]
+ mypy/visitor.py:509: error: Missing return statement  [empty-body]
+ mypy/visitor.py:512: error: Missing return statement  [empty-body]
+ mypy/visitor.py:515: error: Missing return statement  [empty-body]
+ mypy/visitor.py:518: error: Missing return statement  [empty-body]
+ mypy/visitor.py:521: error: Missing return statement  [empty-body]
+ mypy/visitor.py:524: error: Missing return statement  [empty-body]
+ mypy/visitor.py:527: error: Missing return statement  [empty-body]
+ mypy/visitor.py:530: error: Missing return statement  [empty-body]
+ mypy/visitor.py:533: error: Missing return statement  [empty-body]
+ mypy/visitor.py:536: error: Missing return statement  [empty-body]
+ mypy/visitor.py:539: error: Missing return statement  [empty-body]
+ mypy/visitor.py:542: error: Missing return statement  [empty-body]
+ mypy/visitor.py:545: error: Missing return statement  [empty-body]
+ mypy/visitor.py:548: error: Missing return statement  [empty-body]
+ mypy/visitor.py:551: error: Missing return statement  [empty-body]
+ mypy/visitor.py:554: error: Missing return statement  [empty-body]
+ mypy/visitor.py:557: error: Missing return statement  [empty-body]
+ mypy/visitor.py:560: error: Missing return statement  [empty-body]
+ mypy/visitor.py:563: error: Missing return statement  [empty-body]
+ mypy/visitor.py:566: error: Missing return statement  [empty-body]
+ mypy/visitor.py:569: error: Missing return statement  [empty-body]
+ mypy/visitor.py:572: error: Missing return statement  [empty-body]
+ mypy/visitor.py:575: error: Missing return statement  [empty-body]
+ mypy/visitor.py:578: error: Missing return statement  [empty-body]
+ mypy/visitor.py:581: error: Missing return statement  [empty-body]
+ mypy/visitor.py:584: error: Missing return statement  [empty-body]
+ mypy/visitor.py:587: error: Missing return statement  [empty-body]
+ mypy/visitor.py:590: error: Missing return statement  [empty-body]
+ mypy/visitor.py:593: error: Missing return statement  [empty-body]
+ mypy/visitor.py:598: error: Missing return statement  [empty-body]
+ mypy/visitor.py:601: error: Missing return statement  [empty-body]
+ mypy/visitor.py:604: error: Missing return statement  [empty-body]
+ mypy/visitor.py:607: error: Missing return statement  [empty-body]
+ mypy/visitor.py:610: error: Missing return statement  [empty-body]
+ mypy/visitor.py:613: error: Missing return statement  [empty-body]
+ mypy/visitor.py:616: error: Missing return statement  [empty-body]
+ mypy/visitor.py:619: error: Missing return statement  [empty-body]

materialize (https://github.com/MaterializeInc/materialize)
+ misc/python/stubs/docker/__init__.py:20: error: Missing return statement  [empty-body]

websockets (https://github.com/aaugustin/websockets)
+ src/websockets/extensions/base.py:21: error: Missing return statement  [empty-body]
+ src/websockets/extensions/base.py:42: error: Missing return statement  [empty-body]
+ src/websockets/extensions/base.py:64: error: Missing return statement  [empty-body]
+ src/websockets/extensions/base.py:73: error: Missing return statement  [empty-body]
+ src/websockets/extensions/base.py:105: error: Missing return statement  [empty-body]

sublime_debugger (https://github.com/daveleroy/sublime_debugger)
+ modules/ui/html.py:98: error: Missing return statement  [empty-body]
+ modules/dap/configuration.py:19: error: Missing return statement  [empty-body]
+ modules/dap/configuration.py:41: error: Missing return statement  [empty-body]
+ modules/debugger_output_panel.py:267: error: Missing return statement  [empty-body]

rich (https://github.com/Textualize/rich)
+ rich/_null_file.py:62: error: Missing return statement  [empty-body]
+ rich/_null_file.py:62: note: If the method is meant to be abstract, use @abc.abstractmethod

bandersnatch (https://github.com/pypa/bandersnatch)
+ src/bandersnatch_storage_plugins/s3.py: note: In member "get_flock_path" of class "S3Storage":
+ src/bandersnatch_storage_plugins/s3.py:162: error: Missing return statement  [empty-body]

manticore (https://github.com/trailofbits/manticore)
+ manticore/wasm/structure.py:1949: error: Missing return statement  [empty-body]
+ manticore/native/cpu/abstractcpu.py:271: error: Missing return statement  [empty-body]

pandas (https://github.com/pandas-dev/pandas)
+ pandas/core/series.py:4645: error: Missing return statement  [empty-body]
+ pandas/core/frame.py:9404: error: Missing return statement  [empty-body]

poetry (https://github.com/python-poetry/poetry)
+ src/poetry/packages/locker.py:473: error: Missing return statement  [empty-body]

spark (https://github.com/apache/spark)
+ python/pyspark/sql/group.py:173: error: Missing return statement  [empty-body]
+ python/pyspark/sql/group.py:204: error: Missing return statement  [empty-body]
+ python/pyspark/sql/group.py:218: error: Missing return statement  [empty-body]
+ python/pyspark/sql/group.py:266: error: Missing return statement  [empty-body]
+ python/pyspark/sql/group.py:307: error: Missing return statement  [empty-body]
+ python/pyspark/sql/group.py:353: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:91: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:98: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:105: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:112: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:120: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:127: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:134: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:141: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:148: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:155: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints_with_future_annotations.py:196: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:88: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:95: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:102: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:109: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:117: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:124: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:131: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:138: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:145: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:152: error: Missing return statement  [empty-body]
+ python/pyspark/sql/tests/test_pandas_udf_typehints.py:193: error: Missing return statement  [empty-body]

pytest (https://github.com/pytest-dev/pytest)
+ src/_pytest/hookspec.py:741: error: Missing return statement  [empty-body]
+ src/_pytest/hookspec.py:770: error: Missing return statement  [empty-body]
+ src/_pytest/hookspec.py:803: error: Missing return statement  [empty-body]
+ src/_pytest/hookspec.py:883: error: Missing return statement  [empty-body]