view mercurial/diffutil.py @ 50801:c51b178b0b7e

configitems: declare items in a TOML file

Mercurial ships with Rust code that also needs to read from the config.
Having a way of presenting `configitems` to both Python and Rust is needed
to prevent duplication, drift, and have the appropriate devel warnings.

Abstracting away from Python means choosing a config format. No single format
is perfect, and I have yet to come across a developer that doesn't hate all of
them in some way.
Since we have a strict no-dependencies policy for Mercurial, we either need
to use whatever comes with Python, vendor a library, or implement a custom
format ourselves.

Python stdlib means using JSON, which doesn't support comments and isn't great
for humans, or `configparser` which is an obscure, untyped format that nobody
uses and doesn't have a commonplace Rust parser.
Implementing a custom format is error-prone, tedious and subject to the
same issues as picking an existing format.

Vendoring opens us to the vast array of common config formats. The ones
being picked for most modern software are YAML and TOML. YAML is older and
common in the Python community, but TOML is much simpler and less error-prone.
I would much rather be responsible for the <1000 lines of `tomli`, on top of
TOML being the choice of the Rust community, with robust crates for reading it.

The structure of `configitems.toml` is explained inline.

# diffutil.py - utility functions related to diff and patch
#
# Copyright 2006 Brendan Cully <[e-mail]>
# Copyright 2007 Chris Mason <[e-mail]>
# Copyright 2018 Octobus <[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.

import typing

from typing import (
    Any,
    Dict,
    Optional,
)

from .i18n import _

from . import (
    mdiff,
    pycompat,
)

if typing.TYPE_CHECKING:
    from . import ui as uimod

# TODO: narrow the value after the config module is typed
_Opts = Dict[bytes, Any]


def diffallopts(
    ui: "uimod.ui",
    opts: Optional[_Opts] = None,
    untrusted: bool = False,
    section: bytes = b'diff',
    configprefix: bytes = b'',
) -> mdiff.diffopts:
    '''return diffopts with all features supported and parsed'''
    return difffeatureopts(
        ui,
        opts=opts,
        untrusted=untrusted,
        section=section,
        git=True,
        whitespace=True,
        formatchanging=True,
        configprefix=configprefix,
    )


def difffeatureopts(
    ui: "uimod.ui",
    opts: Optional[_Opts] = None,
    untrusted: bool = False,
    section: bytes = b'diff',
    git: bool = False,
    whitespace: bool = False,
    formatchanging: bool = False,
    configprefix: bytes = b'',
) -> mdiff.diffopts:
    """return diffopts with only opted-in features parsed

    Features:
    - git: git-style diffs
    - whitespace: whitespace options like ignoreblanklines and ignorews
    - formatchanging: options that will likely break or cause correctness issues
      with most diff parsers
    """

    def get(
        key: bytes,
        name: Optional[bytes] = None,
        getter=ui.configbool,
        forceplain: Optional[bool] = None,
    ) -> Any:
        if opts:
            v = opts.get(key)
            # diffopts flags are either None-default (which is passed
            # through unchanged, so we can identify unset values), or
            # some other falsey default (eg --unified, which defaults
            # to an empty string). We only want to override the config
            # entries from hgrc with command line values if they
            # appear to have been set, which is any truthy value,
            # True, or False.
            if v or isinstance(v, bool):
                return v
        if forceplain is not None and ui.plain():
            return forceplain
        return getter(
            section, configprefix + (name or key), untrusted=untrusted
        )

    # core options, expected to be understood by every diff parser
    buildopts = {
        b'nodates': get(b'nodates'),
        b'showfunc': get(b'show_function', b'showfunc'),
        b'context': get(b'unified', getter=ui.config),
    }
    buildopts[b'xdiff'] = ui.configbool(b'experimental', b'xdiff')

    if git:
        buildopts[b'git'] = get(b'git')

        # since this is in the experimental section, we need to call
        # ui.configbool directory
        buildopts[b'showsimilarity'] = ui.configbool(
            b'experimental', b'extendedheader.similarity'
        )

        # need to inspect the ui object instead of using get() since we want to
        # test for an int
        hconf = ui.config(b'experimental', b'extendedheader.index')
        if hconf is not None:
            hlen = None
            try:
                # the hash config could be an integer (for length of hash) or a
                # word (e.g. short, full, none)
                hlen = int(hconf)
                if hlen < 0 or hlen > 40:
                    msg = _(b"invalid length for extendedheader.index: '%d'\n")
                    ui.warn(msg % hlen)
            except ValueError:
                # default value
                if hconf == b'short' or hconf == b'':
                    hlen = 12
                elif hconf == b'full':
                    hlen = 40
                elif hconf != b'none':
                    msg = _(b"invalid value for extendedheader.index: '%s'\n")
                    ui.warn(msg % hconf)
            finally:
                buildopts[b'index'] = hlen

    if whitespace:
        buildopts[b'ignorews'] = get(b'ignore_all_space', b'ignorews')
        buildopts[b'ignorewsamount'] = get(
            b'ignore_space_change', b'ignorewsamount'
        )
        buildopts[b'ignoreblanklines'] = get(
            b'ignore_blank_lines', b'ignoreblanklines'
        )
        buildopts[b'ignorewseol'] = get(b'ignore_space_at_eol', b'ignorewseol')
    if formatchanging:
        buildopts[b'text'] = None if opts is None else opts.get(b'text')
        binary = None if opts is None else opts.get(b'binary')
        buildopts[b'nobinary'] = (
            not binary
            if binary is not None
            else get(b'nobinary', forceplain=False)
        )
        buildopts[b'noprefix'] = get(b'noprefix', forceplain=False)
        buildopts[b'worddiff'] = get(
            b'word_diff', b'word-diff', forceplain=False
        )

    return mdiff.diffopts(**pycompat.strkwargs(buildopts))