summaryrefslogtreecommitdiffstats
path: root/pre_commit_hooks/fix_encoding_pragma.py
blob: 60c71eeb84dc997298ce2c0bce4cf800afc26275 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
from __future__ import annotations

import argparse
from typing import IO
from typing import NamedTuple
from typing import Sequence

DEFAULT_PRAGMA = b'# -*- coding: utf-8 -*-'


def has_coding(line: bytes) -> bool:
    if not line.strip():
        return False
    return (
        line.lstrip()[:1] == b'#' and (
            b'unicode' in line or
            b'encoding' in line or
            b'coding:' in line or
            b'coding=' in line
        )
    )


class ExpectedContents(NamedTuple):
    shebang: bytes
    rest: bytes
    # True: has exactly the coding pragma expected
    # False: missing coding pragma entirely
    # None: has a coding pragma, but it does not match
    pragma_status: bool | None
    ending: bytes

    @property
    def has_any_pragma(self) -> bool:
        return self.pragma_status is not False

    def is_expected_pragma(self, remove: bool) -> bool:
        expected_pragma_status = not remove
        return self.pragma_status is expected_pragma_status


def _get_expected_contents(
        first_line: bytes,
        second_line: bytes,
        rest: bytes,
        expected_pragma: bytes,
) -> ExpectedContents:
    ending = b'\r\n' if first_line.endswith(b'\r\n') else b'\n'

    if first_line.startswith(b'#!'):
        shebang = first_line
        potential_coding = second_line
    else:
        shebang = b''
        potential_coding = first_line
        rest = second_line + rest

    if potential_coding.rstrip(b'\r\n') == expected_pragma:
        pragma_status: bool | None = True
    elif has_coding(potential_coding):
        pragma_status = None
    else:
        pragma_status = False
        rest = potential_coding + rest

    return ExpectedContents(
        shebang=shebang, rest=rest, pragma_status=pragma_status, ending=ending,
    )


def fix_encoding_pragma(
        f: IO[bytes],
        remove: bool = False,
        expected_pragma: bytes = DEFAULT_PRAGMA,
) -> int:
    expected = _get_expected_contents(
        f.readline(), f.readline(), f.read(), expected_pragma,
    )

    # Special cases for empty files
    if not expected.rest.strip():
        # If a file only has a shebang or a coding pragma, remove it
        if expected.has_any_pragma or expected.shebang:
            f.seek(0)
            f.truncate()
            f.write(b'')
            return 1
        else:
            return 0

    if expected.is_expected_pragma(remove):
        return 0

    # Otherwise, write out the new file
    f.seek(0)
    f.truncate()
    f.write(expected.shebang)
    if not remove:
        f.write(expected_pragma + expected.ending)
    f.write(expected.rest)

    return 1


def _normalize_pragma(pragma: str) -> bytes:
    return pragma.encode().rstrip()


def main(argv: Sequence[str] | None = None) -> int:
    parser = argparse.ArgumentParser(
        'Fixes the encoding pragma of python files',
    )
    parser.add_argument('filenames', nargs='*', help='Filenames to fix')
    parser.add_argument(
        '--pragma', default=DEFAULT_PRAGMA, type=_normalize_pragma,
        help=(
            f'The encoding pragma to use.  '
            f'Default: {DEFAULT_PRAGMA.decode()}'
        ),
    )
    parser.add_argument(
        '--remove', action='store_true',
        help='Remove the encoding pragma (Useful in a python3-only codebase)',
    )
    args = parser.parse_args(argv)

    retv = 0

    if args.remove:
        fmt = 'Removed encoding pragma from {filename}'
    else:
        fmt = 'Added `{pragma}` to {filename}'

    for filename in args.filenames:
        with open(filename, 'r+b') as f:
            file_ret = fix_encoding_pragma(
                f, remove=args.remove, expected_pragma=args.pragma,
            )
            retv |= file_ret
            if file_ret:
                print(
                    fmt.format(pragma=args.pragma.decode(), filename=filename),
                )

    return retv


if __name__ == '__main__':
    raise SystemExit(main())