hgext/highlight/highlight.py

git: skeleton of a new extension to _directly_ operate on git repos

This is based in part of work I did years ago in hgit, but it's mostly
new code since I'm using pygit2 instead of dulwich and the hg storage
interfaces have improved. Some cleanup of old hgit code by Pulkit,
which I greatly appreciate.

test-git-interop.t does not cover a whole lot of cases, but it
passes. It includes status, diff, making a new commit, and `hg annotate`
working on the git repository.

This is _not_ (yet) production quality code: this is an
experiment. Known technical debt lurking in this implementation:

 * Writing bookmarks just totally ignores transactions.
 * The way progress is threaded down into the gitstore is awful.
 * Ideally we'd find a way to incrementally reindex DAGs. I'm not sure
   how to do that efficiently, so we might need a "known only fast-forwards"
   mode on the DAG indexer for use on `hg commit` and friends.
 * We don't even _try_ to do anything reasonable for `hg pull` or `hg push`.
 * Mercurial need an interface for the changelog type.

Tests currently require git 2.24 as far as I'm aware: `git status` has
some changed output that I didn't try and handle in a compatible way.

This patch has produced some interesting cleanups, most recently on
the manifest type. I expect continuing down this road will produce
other meritorious cleanups throughout our code.

Differential Revision: https://phab.mercurial-scm.org/D6734

# highlight.py - highlight extension implementation file
#
#  Copyright 2007-2009 Adam Hupp <[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 original module was split in an interface and an implementation
# file to defer pygments loading and speedup extension setup.

from __future__ import absolute_import

from mercurial import demandimport

demandimport.IGNORES.update([b'pkgutil', b'pkg_resources', b'__main__'])

from mercurial import (
    encoding,
    pycompat,
)

from mercurial.utils import stringutil

with demandimport.deactivated():
    import pygments
    import pygments.formatters
    import pygments.lexers
    import pygments.plugin
    import pygments.util

    for unused in pygments.plugin.find_plugin_lexers():
        pass

highlight = pygments.highlight
ClassNotFound = pygments.util.ClassNotFound
guess_lexer = pygments.lexers.guess_lexer
guess_lexer_for_filename = pygments.lexers.guess_lexer_for_filename
TextLexer = pygments.lexers.TextLexer
HtmlFormatter = pygments.formatters.HtmlFormatter

SYNTAX_CSS = (
    b'\n<link rel="stylesheet" href="{url}highlightcss" type="text/css" />'
)


def pygmentize(field, fctx, style, tmpl, guessfilenameonly=False):

    # append a <link ...> to the syntax highlighting css
    tmpl.load(b'header')
    old_header = tmpl.cache[b'header']
    if SYNTAX_CSS not in old_header:
        new_header = old_header + SYNTAX_CSS
        tmpl.cache[b'header'] = new_header

    text = fctx.data()
    if stringutil.binary(text):
        return

    # str.splitlines() != unicode.splitlines() because "reasons"
    for c in b"\x0c", b"\x1c", b"\x1d", b"\x1e":
        if c in text:
            text = text.replace(c, b'')

    # Pygments is best used with Unicode strings:
    # <http://pygments.org/docs/unicode/>
    text = text.decode(pycompat.sysstr(encoding.encoding), 'replace')

    # To get multi-line strings right, we can't format line-by-line
    try:
        path = pycompat.sysstr(fctx.path())
        lexer = guess_lexer_for_filename(path, text[:1024], stripnl=False)
    except (ClassNotFound, ValueError):
        # guess_lexer will return a lexer if *any* lexer matches. There is
        # no way to specify a minimum match score. This can give a high rate of
        # false positives on files with an unknown filename pattern.
        if guessfilenameonly:
            return

        try:
            lexer = guess_lexer(text[:1024], stripnl=False)
        except (ClassNotFound, ValueError):
            # Don't highlight unknown files
            return

    # Don't highlight text files
    if isinstance(lexer, TextLexer):
        return

    formatter = HtmlFormatter(nowrap=True, style=pycompat.sysstr(style))

    colorized = highlight(text, lexer, formatter)
    coloriter = (
        s.encode(pycompat.sysstr(encoding.encoding), 'replace')
        for s in colorized.splitlines()
    )

    tmpl._filters[b'colorize'] = lambda x: next(coloriter)

    oldl = tmpl.cache[field]
    newl = oldl.replace(b'line|escape', b'line|colorize')
    tmpl.cache[field] = newl