contrib/check-config.py

rhg: Don’t compare ambiguous files one byte at a time

Even though the use of `BufReader` reduces the number of syscalls to read
the file from disk, `.bytes()` yields a separate `Result` for every byte.
Creating those results and dispatching on them is most likely costly.

Instead, this commit opts for simplicity by reading the entire file into memory
and comparing a single pair of byte strings. Note that memory already needs to
contain the entire previous contents of the file, as read from the filelog.
So with an extremely large file this doubles memory use but does not make it
grow by orders of magnitude.

At first I wrote code that still avoids reading the entire file into memory
and compares one buffer at a time with `BufReader`. Find this code below for
posterity. However its correctness is subtle. I ended up preferring the
simplicity of the obviously-correct single comparison.

```rust
let mut reader = BufReader::new(fobj);
let mut expected = &contents_in_p1[..];
loop {
    let buf = reader.fill_buf().when_reading_file(&fs_path)?;
    if buf.is_empty() {
        // Found EOF
        return Ok(expected.is_empty());
    } else if let Some(rest) = expected.drop_prefix(buf) {
        // What we read so far matches the expected content, continue reading
        let buf_len = buf.len();
        reader.consume(buf_len);
        expected = rest
    } else {
        // Found different content
        return Ok(false);
    }
}
```

Differential Revision: https://phab.mercurial-scm.org/D11412

#!/usr/bin/env python3
#
# check-config - a config flag documentation checker for Mercurial
#
# Copyright 2015 Olivia Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import, print_function
import re
import sys

foundopts = {}
documented = {}
allowinconsistent = set()

configre = re.compile(
    br'''
    # Function call
    ui\.config(?P<ctype>|int|bool|list)\(
        # First argument.
        ['"](?P<section>\S+)['"],\s*
        # Second argument
        ['"](?P<option>\S+)['"](,\s+
        (?:default=)?(?P<default>\S+?))?
    \)''',
    re.VERBOSE | re.MULTILINE,
)

configwithre = re.compile(
    br'''
    ui\.config(?P<ctype>with)\(
        # First argument is callback function. This doesn't parse robustly
        # if it is e.g. a function call.
        [^,]+,\s*
        ['"](?P<section>\S+)['"],\s*
        ['"](?P<option>\S+)['"](,\s+
        (?:default=)?(?P<default>\S+?))?
    \)''',
    re.VERBOSE | re.MULTILINE,
)

configpartialre = br"""ui\.config"""

ignorere = re.compile(
    br'''
    \#\s(?P<reason>internal|experimental|deprecated|developer|inconsistent)\s
    config:\s(?P<config>\S+\.\S+)$
    ''',
    re.VERBOSE | re.MULTILINE,
)

if sys.version_info[0] > 2:

    def mkstr(b):
        if isinstance(b, str):
            return b
        return b.decode('utf8')


else:
    mkstr = lambda x: x


def main(args):
    for f in args:
        sect = b''
        prevname = b''
        confsect = b''
        carryover = b''
        linenum = 0
        for l in open(f, 'rb'):
            linenum += 1

            # check topic-like bits
            m = re.match(br'\s*``(\S+)``', l)
            if m:
                prevname = m.group(1)
            if re.match(br'^\s*-+$', l):
                sect = prevname
                prevname = b''

            if sect and prevname:
                name = sect + b'.' + prevname
                documented[name] = 1

            # check docstring bits
            m = re.match(br'^\s+\[(\S+)\]', l)
            if m:
                confsect = m.group(1)
                continue
            m = re.match(br'^\s+(?:#\s*)?(\S+) = ', l)
            if m:
                name = confsect + b'.' + m.group(1)
                documented[name] = 1

            # like the bugzilla extension
            m = re.match(br'^\s*(\S+\.\S+)$', l)
            if m:
                documented[m.group(1)] = 1

            # like convert
            m = re.match(br'^\s*:(\S+\.\S+):\s+', l)
            if m:
                documented[m.group(1)] = 1

            # quoted in help or docstrings
            m = re.match(br'.*?``(\S+\.\S+)``', l)
            if m:
                documented[m.group(1)] = 1

            # look for ignore markers
            m = ignorere.search(l)
            if m:
                if m.group('reason') == b'inconsistent':
                    allowinconsistent.add(m.group('config'))
                else:
                    documented[m.group('config')] = 1

            # look for code-like bits
            line = carryover + l
            m = configre.search(line) or configwithre.search(line)
            if m:
                ctype = m.group('ctype')
                if not ctype:
                    ctype = 'str'
                name = m.group('section') + b"." + m.group('option')
                default = m.group('default')
                if default in (
                    None,
                    b'False',
                    b'None',
                    b'0',
                    b'[]',
                    b'""',
                    b"''",
                ):
                    default = b''
                if re.match(b'[a-z.]+$', default):
                    default = b'<variable>'
                if (
                    name in foundopts
                    and (ctype, default) != foundopts[name]
                    and name not in allowinconsistent
                ):
                    print(mkstr(l.rstrip()))
                    fctype, fdefault = foundopts[name]
                    print(
                        "conflict on %s: %r != %r"
                        % (
                            mkstr(name),
                            (mkstr(ctype), mkstr(default)),
                            (mkstr(fctype), mkstr(fdefault)),
                        )
                    )
                    print("at %s:%d:" % (mkstr(f), linenum))
                foundopts[name] = (ctype, default)
                carryover = b''
            else:
                m = re.search(configpartialre, line)
                if m:
                    carryover = line
                else:
                    carryover = b''

    for name in sorted(foundopts):
        if name not in documented:
            if not (
                name.startswith(b"devel.")
                or name.startswith(b"experimental.")
                or name.startswith(b"debug.")
            ):
                ctype, default = foundopts[name]
                if default:
                    if isinstance(default, bytes):
                        default = mkstr(default)
                    default = ' [%s]' % default
                elif isinstance(default, bytes):
                    default = mkstr(default)
                print(
                    "undocumented: %s (%s)%s"
                    % (mkstr(name), mkstr(ctype), default)
                )


if __name__ == "__main__":
    if len(sys.argv) > 1:
        sys.exit(main(sys.argv[1:]))
    else:
        sys.exit(main([l.rstrip() for l in sys.stdin]))