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Mitigate deprecation of aiohttp's `@middleware` decorator (#3259)
[etc/vim.git] / scripts / fuzz.py
1 """Property-based tests for Black.
2
3 By Zac Hatfield-Dodds, based on my Hypothesmith tool for source code
4 generation.  You can run this file with `python`, `pytest`, or (soon)
5 a coverage-guided fuzzer I'm working on.
6 """
7
8 import re
9
10 import hypothesmith
11 from hypothesis import HealthCheck, given, settings
12 from hypothesis import strategies as st
13
14 import black
15 from blib2to3.pgen2.tokenize import TokenError
16
17
18 # This test uses the Hypothesis and Hypothesmith libraries to generate random
19 # syntatically-valid Python source code and run Black in odd modes.
20 @settings(
21     max_examples=1000,  # roughly 1k tests/minute, or half that under coverage
22     derandomize=True,  # deterministic mode to avoid CI flakiness
23     deadline=None,  # ignore Hypothesis' health checks; we already know that
24     suppress_health_check=HealthCheck.all(),  # this is slow and filter-heavy.
25 )
26 @given(
27     # Note that while Hypothesmith might generate code unlike that written by
28     # humans, it's a general test that should pass for any *valid* source code.
29     # (so e.g. running it against code scraped of the internet might also help)
30     src_contents=hypothesmith.from_grammar() | hypothesmith.from_node(),
31     # Using randomly-varied modes helps us to exercise less common code paths.
32     mode=st.builds(
33         black.FileMode,
34         line_length=st.just(88) | st.integers(0, 200),
35         string_normalization=st.booleans(),
36         preview=st.booleans(),
37         is_pyi=st.booleans(),
38         magic_trailing_comma=st.booleans(),
39     ),
40 )
41 def test_idempotent_any_syntatically_valid_python(
42     src_contents: str, mode: black.FileMode
43 ) -> None:
44     # Before starting, let's confirm that the input string is valid Python:
45     compile(src_contents, "<string>", "exec")  # else the bug is in hypothesmith
46
47     # Then format the code...
48     try:
49         dst_contents = black.format_str(src_contents, mode=mode)
50     except black.InvalidInput:
51         # This is a bug - if it's valid Python code, as above, Black should be
52         # able to cope with it.  See issues #970, #1012
53         # TODO: remove this try-except block when issues are resolved.
54         return
55     except TokenError as e:
56         if (  # Special-case logic for backslashes followed by newlines or end-of-input
57             e.args[0] == "EOF in multi-line statement"
58             and re.search(r"\\($|\r?\n)", src_contents) is not None
59         ):
60             # This is a bug - if it's valid Python code, as above, Black should be
61             # able to cope with it.  See issue #1012.
62             # TODO: remove this block when the issue is resolved.
63             return
64         raise
65
66     # And check that we got equivalent and stable output.
67     black.assert_equivalent(src_contents, dst_contents)
68     black.assert_stable(src_contents, dst_contents, mode=mode)
69
70     # Future test: check that pure-python and mypyc versions of black
71     # give identical output for identical input?
72
73
74 if __name__ == "__main__":
75     # Run tests, including shrinking and reporting any known failures.
76     test_idempotent_any_syntatically_valid_python()
77
78     # If Atheris is available, run coverage-guided fuzzing.
79     # (if you want only bounded fuzzing, just use `pytest fuzz.py`)
80     try:
81         import sys
82
83         import atheris
84     except ImportError:
85         pass
86     else:
87         test = test_idempotent_any_syntatically_valid_python
88         atheris.Setup(
89             sys.argv,
90             test.hypothesis.fuzz_one_input,  # type: ignore[attr-defined]
91         )
92         atheris.Fuzz()