config: type `rcutil`

It helps to understand what is going on here and catch future errors.

mercurial/configuration/rcutil.py

@@ -1,119 +1,139
 # rcutil.py - utilities about config paths, special config sections etc.
 #
 #  Copyright Mercurial Contributors
 #
 # 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 annotations
 
 import os
 
+from typing import (
+    Dict,
+    List,
+    Optional,
+    Tuple,
+    Union,
+)
+
 from .. import (
     encoding,
     pycompat,
     util,
 )
 
 from ..utils import resourceutil
 
 if pycompat.iswindows:
     from .. import scmwindows as scmplatform
 else:
     from .. import scmposix as scmplatform
 
 fallbackpager = scmplatform.fallbackpager
 systemrcpath = scmplatform.systemrcpath
 userrcpath = scmplatform.userrcpath
 
+ConfigItemT = Tuple[bytes, bytes, bytes, bytes]
+ResourceIDT = Tuple[bytes, bytes]
+FileRCT = bytes
+ComponentT = Tuple[
+    bytes,
+    Union[
+        List[ConfigItemT],
+        FileRCT,
+        ResourceIDT,
+    ],
+]
 
-def _expandrcpath(path):
+
+def _expandrcpath(path: bytes) -> List[FileRCT]:
     '''path could be a file or a directory. return a list of file paths'''
     p = util.expandpath(path)
     if os.path.isdir(p):
         join = os.path.join
         return sorted(
             join(p, f) for f, k in util.listdir(p) if f.endswith(b'.rc')
         )
     return [p]
 
 
-def envrcitems(env=None):
+def envrcitems(env: Optional[Dict[bytes, bytes]] = None) -> List[ConfigItemT]:
     """Return [(section, name, value, source)] config items.
 
     The config items are extracted from environment variables specified by env,
     used to override systemrc, but not userrc.
 
     If env is not provided, encoding.environ will be used.
     """
     if env is None:
         env = encoding.environ
     checklist = [
         (b'EDITOR', b'ui', b'editor'),
         (b'VISUAL', b'ui', b'editor'),
         (b'PAGER', b'pager', b'pager'),
     ]
     result = []
     for envname, section, configname in checklist:
         if envname not in env:
             continue
         result.append((section, configname, env[envname], b'$%s' % envname))
     return result
 
 
-def default_rc_resources():
+def default_rc_resources() -> List[ResourceIDT]:
     """return rc resource IDs in defaultrc"""
     rsrcs = resourceutil.contents(b'mercurial.defaultrc')
     return [
         (b'mercurial.defaultrc', r)
         for r in sorted(rsrcs)
         if resourceutil.is_resource(b'mercurial.defaultrc', r)
         and r.endswith(b'.rc')
     ]
 
 
-def rccomponents():
+def rccomponents() -> List[ComponentT]:
     """return an ordered [(type, obj)] about where to load configs.
 
     respect $HGRCPATH. if $HGRCPATH is empty, only .hg/hgrc of current repo is
     used. if $HGRCPATH is not set, the platform default will be used.
 
     if a directory is provided, *.rc files under it will be used.
 
     type could be either 'path', 'items' or 'resource'. If type is 'path',
     obj is a string, and is the config file path. if type is 'items', obj is a
     list of (section, name, value, source) that should fill the config directly.
     If type is 'resource', obj is a tuple of (package name, resource name).
     """
     envrc = (b'items', envrcitems())
 
     if b'HGRCPATH' in encoding.environ:
         # assume HGRCPATH is all about user configs so environments can be
         # overridden.
         _rccomponents = [envrc]
         for p in encoding.environ[b'HGRCPATH'].split(pycompat.ospathsep):
             if not p:
                 continue
             _rccomponents.extend((b'path', p) for p in _expandrcpath(p))
     else:
         _rccomponents = [(b'resource', r) for r in default_rc_resources()]
 
         normpaths = lambda paths: [
             (b'path', os.path.normpath(p)) for p in paths
         ]
         _rccomponents.extend(normpaths(systemrcpath()))
         _rccomponents.append(envrc)
         _rccomponents.extend(normpaths(userrcpath()))
     return _rccomponents
 
 
-def defaultpagerenv():
+def defaultpagerenv() -> Dict[bytes, bytes]:
     """return a dict of default environment variables and their values,
     intended to be set before starting a pager.
     """
     return {b'LESS': b'FRX', b'LV': b'-c'}
 
 
-def use_repo_hgrc():
+def use_repo_hgrc() -> bool:
     """True if repositories `.hg/hgrc` config should be read"""
     return b'HGRCSKIPREPO' not in encoding.environ