typing: add typehints to mercurial/diffutil.py

Lack of typehints here caused the fact that TortoiseHg was passing str instead
of bytes as the key in `opts` to be missed, resulting in shelf corruption in
cases where `diff.git` is required.

mercurial/diffutil.py

@@ -1,135 +1,157 b''
 # 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, opts=None, untrusted=False, section=b'diff', configprefix=b''
-):
+    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,
-    opts=None,
-    untrusted=False,
-    section=b'diff',
-    git=False,
-    whitespace=False,
-    formatchanging=False,
-    configprefix=b'',
-):
+    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, name=None, getter=ui.configbool, forceplain=None):
+    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'] = opts and 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))