i18n/hggettext

mdiff: speed up showfunc for large diffs

This addresses the following issues with showfunc:

- Silly usage of regular expressions.
- Doing str.rstrip() needlessly in an inner loop.
- Doing catastrophic backtracking when trying to find a function line.

Finding function text is now at worst O(n lines in the old file), and
at best close to O(n hunks).

Given a diff like this[1]:

 src/main/antlr3/uk/ac/cam/ch/wwmm/pregenerated/ChemicalChunker.g        |      4 +-
 src/main/java/uk/ac/cam/ch/wwmm/pregenerated/ChemicalChunkerLexer.java  |      2 +-
 src/main/java/uk/ac/cam/ch/wwmm/pregenerated/ChemicalChunkerParser.java |  29189 +++++----
 3 files changed, 14741 insertions(+), 14454 deletions(-)

[1]: https://bitbucket.org/wwmm/chemicaltagger/changeset/d2bfbaecd4fc/raw

Without this change, hg log --stat --config diff.showfunc=1 takes an
absurdly long time to complete:

   CallCount    Recursive    Total(ms)   Inline(ms) module:lineno(function)
       32813            0     80.3546     40.6086   mercurial.mdiff:160(yieldhunk)
   [phone]            0     25.7227     25.7227   +<method 'match' of '_sre.SRE_Pattern' objects>
   [phone]            0     14.0221     14.0221   +<method 'rstrip' of 'str' objects>
       +1809            0      0.0009      0.0009   +mercurial.mdiff:148(contextend)
       +1809            0      0.0003      0.0003   +<len>
    65062746            0     25.7227     25.7227   <method 'match' of '_sre.SRE_Pattern' objects>
    65062763            0     14.0221     14.0221   <method 'rstrip' of 'str' objects>
         543            0      0.1631      0.1631   <zlib.decompress>
           3            0      0.0505      0.0505   <mercurial.bdiff.blocks>
       31007            0     80.4564      0.0477   mercurial.mdiff:147(_unidiff)
      +32813            0     80.3546     40.6086   +mercurial.mdiff:160(yieldhunk)
          +3            0      0.0505      0.0505   +<mercurial.bdiff.blocks>
       +3618            0      0.0022      0.0022   +mercurial.mdiff:154(contextstart)
       +5427            0      0.0013      0.0013   +<len>
          +3            0      0.0001      0.0000   +re:188(compile)
           1            0     80.8381      0.0322   mercurial.patch:1777(diffstatdata)
     +107499            0      0.0235      0.0235   +<method 'startswith' of 'str' objects>
      +31014            0     80.7820      0.0071   +mercurial.util:1284(iterlines)
          +3            0      0.0000      0.0000   +<method 'search' of '_sre.SRE_Pattern' objects>
          +4            0      0.0000      0.0000   +mercurial.patch:1783(addresult)
          +3            0      0.0000      0.0000   +<method 'group' of '_sre.SRE_Match' objects>
           6            0      0.0444      0.0283   mercurial.mdiff:12(splitnewlines)
          +6            0      0.0160      0.0160   +<method 'split' of 'str' objects>
          32            0      0.0246      0.0246   <method 'update' of '_hashlib.HASH' objects>
          11            0      0.0236      0.0236   <method 'read' of 'file' objects>
Time: real 80.880 secs (user 80.200+0.000 sys 0.380+0.000)

With this change, it's almost as fast as not using showfunc at all:

   CallCount    Recursive    Total(ms)   Inline(ms) module:lineno(function)
         543            0      0.1699      0.1699   <zlib.decompress>
           3            0      0.0501      0.0501   <mercurial.bdiff.blocks>
       32813            0      0.0415      0.0348   mercurial.mdiff:161(yieldhunk)
      +70837            0      0.0058      0.0058   +<method 'isalnum' of 'str' objects>
       +1809            0      0.0006      0.0006   +mercurial.mdiff:148(contextend)
       +1809            0      0.0002      0.0002   +<len>
           1            0      0.4879      0.0310   mercurial.patch:1777(diffstatdata)
     +107499            0      0.0230      0.0230   +<method 'startswith' of 'str' objects>
      +31014            0      0.4335      0.0065   +mercurial.util:1284(iterlines)
          +3            0      0.0000      0.0000   +<method 'search' of '_sre.SRE_Pattern' objects>
          +4            0      0.0000      0.0000   +mercurial.patch:1783(addresult)
          +1            0      0.0004      0.0000   +re:188(compile)
          32            0      0.0293      0.0293   <method 'update' of '_hashlib.HASH' objects>
           6            0      0.0427      0.0279   mercurial.mdiff:12(splitnewlines)
          +6            0      0.0147      0.0147   +<method 'split' of 'str' objects>
       31007            0      0.1169      0.0235   mercurial.mdiff:147(_unidiff)
          +3            0      0.0501      0.0501   +<mercurial.bdiff.blocks>
      +32813            0      0.0415      0.0348   +mercurial.mdiff:161(yieldhunk)
       +3618            0      0.0012      0.0012   +mercurial.mdiff:154(contextstart)
       +5427            0      0.0006      0.0006   +<len>
      107597            0      0.0230      0.0230   <method 'startswith' of 'str' objects>
          16            0      0.0213      0.0213   <mercurial.mpatch.patches>
         194            0      0.0149      0.0149   <method 'split' of 'str' objects>
Time: real 0.530 secs (user 0.450+0.000 sys 0.070+0.000)

#!/usr/bin/env python
#
# hggettext - carefully extract docstrings for Mercurial
#
# Copyright 2009 Matt Mackall <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# The normalize function is taken from pygettext which is distributed
# with Python under the Python License, which is GPL compatible.

"""Extract docstrings from Mercurial commands.

Compared to pygettext, this script knows about the cmdtable and table
dictionaries used by Mercurial, and will only extract docstrings from
functions mentioned therein.

Use xgettext like normal to extract strings marked as translatable and
join the message cataloges to get the final catalog.
"""

import os, sys, inspect


def escape(s):
    # The order is important, the backslash must be escaped first
    # since the other replacements introduce new backslashes
    # themselves.
    s = s.replace('\\', '\\\\')
    s = s.replace('\n', '\\n')
    s = s.replace('\r', '\\r')
    s = s.replace('\t', '\\t')
    s = s.replace('"', '\\"')
    return s


def normalize(s):
    # This converts the various Python string types into a format that
    # is appropriate for .po files, namely much closer to C style.
    lines = s.split('\n')
    if len(lines) == 1:
        s = '"' + escape(s) + '"'
    else:
        if not lines[-1]:
            del lines[-1]
            lines[-1] = lines[-1] + '\n'
        lines = map(escape, lines)
        lineterm = '\\n"\n"'
        s = '""\n"' + lineterm.join(lines) + '"'
    return s


def poentry(path, lineno, s):
    return ('#: %s:%d\n' % (path, lineno) +
            'msgid %s\n' % normalize(s) +
            'msgstr ""\n')


def offset(src, doc, name, default):
    """Compute offset or issue a warning on stdout."""
    # Backslashes in doc appear doubled in src.
    end = src.find(doc.replace('\\', '\\\\'))
    if end == -1:
        # This can happen if the docstring contains unnecessary escape
        # sequences such as \" in a triple-quoted string. The problem
        # is that \" is turned into " and so doc wont appear in src.
        sys.stderr.write("warning: unknown offset in %s, assuming %d lines\n"
                         % (name, default))
        return default
    else:
        return src.count('\n', 0, end)


def importpath(path):
    """Import a path like foo/bar/baz.py and return the baz module."""
    if path.endswith('.py'):
        path = path[:-3]
    if path.endswith('/__init__'):
        path = path[:-9]
    path = path.replace('/', '.')
    mod = __import__(path)
    for comp in path.split('.')[1:]:
        mod = getattr(mod, comp)
    return mod


def docstrings(path):
    """Extract docstrings from path.

    This respects the Mercurial cmdtable/table convention and will
    only extract docstrings from functions mentioned in these tables.
    """
    mod = importpath(path)
    if mod.__doc__:
        src = open(path).read()
        lineno = 1 + offset(src, mod.__doc__, path, 7)
        print poentry(path, lineno, mod.__doc__)

    functions = list(getattr(mod, 'i18nfunctions', []))
    functions = [(f, True) for f in functions]

    cmdtable = getattr(mod, 'cmdtable', {})
    if not cmdtable:
        # Maybe we are processing mercurial.commands?
        cmdtable = getattr(mod, 'table', {})
    functions.extend((c[0], False) for c in cmdtable.itervalues())

    for func, rstrip in functions:
        if func.__doc__:
            src = inspect.getsource(func)
            name = "%s.%s" % (path, func.__name__)
            lineno = func.func_code.co_firstlineno
            doc = func.__doc__
            if rstrip:
                doc = doc.rstrip()
            lineno += offset(src, doc, name, 1)
            print poentry(path, lineno, doc)


def rawtext(path):
    src = open(path).read()
    print poentry(path, 1, src)


if __name__ == "__main__":
    # It is very important that we import the Mercurial modules from
    # the source tree where hggettext is executed. Otherwise we might
    # accidentally import and extract strings from a Mercurial
    # installation mentioned in PYTHONPATH.
    sys.path.insert(0, os.getcwd())
    from mercurial import demandimport; demandimport.enable()
    for path in sys.argv[1:]:
        if path.endswith('.txt'):
            rawtext(path)
        else:
            docstrings(path)