typing: add type hints to `mercurial.dirstatemap`

Somewhere since 10db46e128d4, pytype stopped being able to infer the type of the
`identity` field.  Fill in some obvious other hints along the way.

These hints caused pytype to flag a missing attribute:

    File "/mnt/c/Users/Matt/hg/mercurial/dirstatemap.py", line 714, in _v1_map:
          No attribute 'stat' on mercurial.windows.cachestat [attribute-error]
      In Union[Any, mercurial.posix.cachestat, mercurial.windows.cachestat]
    File "/mnt/c/Users/Matt/hg/mercurial/dirstatemap.py", line 715, in _v1_map:
          No attribute 'stat' on mercurial.windows.cachestat [attribute-error]
      In Union[Any, mercurial.posix.cachestat, mercurial.windows.cachestat]

In practice, the `identity` field is NOT replaced with None if it isn't
cacheable, so it's probably safer to just add the field and set it to None,
since that check is already in place on line 715.

mercurial/dirstatemap.py

@@ -4,6 +4,11 b''
 # GNU General Public License version 2 or any later version.
 
 
+from typing import (
+    Optional,
+    TYPE_CHECKING,
+)
+
 from .i18n import _
 
 from . import (
@@ -12,6 +17,7 b' from . import ('
     policy,
     testing,
     txnutil,
+    typelib,
     util,
 )
 
@@ -20,6 +26,11 b' from .dirstateutils import ('
     v2,
 )
 
+if TYPE_CHECKING:
+    from . import (
+        ui as uimod,
+    )
+
 parsers = policy.importmod('parsers')
 rustmod = policy.importrust('dirstate')
 
@@ -46,12 +57,31 b' class _dirstatemapcommon:'
     class, with and without Rust extensions enabled.
     """
 
+    _use_dirstate_v2: bool
+    _nodeconstants: typelib.NodeConstants
+    _ui: "uimod.ui"
+    _root: bytes
+    _filename: bytes
+    _nodelen: int
+    _dirtyparents: bool
+    _docket: Optional["docketmod.DirstateDocket"]
+    _write_mode: int
+    _pendingmode: Optional[bool]
+    identity: Optional[typelib.CacheStat]
+
     # please pytype
 
     _map = None
     copymap = None
 
-    def __init__(self, ui, opener, root, nodeconstants, use_dirstate_v2):
+    def __init__(
+        self,
+        ui: "uimod.ui",
+        opener,
+        root: bytes,
+        nodeconstants: typelib.NodeConstants,
+        use_dirstate_v2: bool,
+    ) -> None:
         self._use_dirstate_v2 = use_dirstate_v2
         self._nodeconstants = nodeconstants
         self._ui = ui
@@ -76,16 +106,16 b' class _dirstatemapcommon:'
         # for consistent view between _pl() and _read() invocations
         self._pendingmode = None
 
-    def _set_identity(self):
+    def _set_identity(self) -> None:
         self.identity = self._get_current_identity()
 
-    def _get_current_identity(self):
+    def _get_current_identity(self) -> Optional[typelib.CacheStat]:
         try:
             return util.cachestat(self._opener.join(self._filename))
         except FileNotFoundError:
             return None
 
-    def may_need_refresh(self):
+    def may_need_refresh(self) -> bool:
         if 'identity' not in vars(self):
             # no existing identity, we need a refresh
             return True
@@ -104,7 +134,7 b' class _dirstatemapcommon:'
             return True
         return current_identity != self.identity
 
-    def preload(self):
+    def preload(self) -> None:
         """Loads the underlying data, if it's not already loaded"""
         self._map
 
@@ -135,7 +165,7 b' class _dirstatemapcommon:'
         self._pendingmode = mode
         return fp
 
-    def _readdirstatefile(self, size=-1):
+    def _readdirstatefile(self, size: int = -1) -> bytes:
         try:
             with self._opendirstatefile() as fp:
                 return fp.read(size)
@@ -144,7 +174,7 b' class _dirstatemapcommon:'
             return b''
 
     @property
-    def docket(self):
+    def docket(self) -> "docketmod.DirstateDocket":
         if not self._docket:
             if not self._use_dirstate_v2:
                 raise error.ProgrammingError(

mercurial/posix.py

@@ -707,6 +707,8 b' def hidewindow() -> None:'
 
 
 class cachestat:
+    stat: os.stat_result
+
     def __init__(self, path: bytes) -> None:
         self.stat = os.stat(path)
 

mercurial/typelib.py

@@ -21,8 +21,21 b' TYPE_CHECKING = typing.TYPE_CHECKING'
 if TYPE_CHECKING:
     from typing import (
         BinaryIO,
+        Union,
+    )
+
+    from . import (
+        node,
+        posix,
+        windows,
     )
 
     BinaryIO_Proxy = BinaryIO
+    CacheStat = Union[posix.cachestat, windows.cachestat]
+    NodeConstants = node.sha1nodeconstants
 else:
+    from typing import Any
+
     BinaryIO_Proxy = object
+    CacheStat = Any
+    NodeConstants = Any

mercurial/windows.py

@@ -675,8 +675,10 b' def isexec(f: bytes) -> bool:'
 
 
 class cachestat:
+    stat: Optional[os.stat_result]
+
     def __init__(self, path: bytes) -> None:
-        pass
+        self.stat = None
 
     def cacheable(self) -> bool:
         return False