interpreter: DEPFILE_KW should be Optional[str]

mesonbuild/interpreter/kwargs.py

@@ -88,7 +88,7 @@ class FuncGenerator(TypedDict):
 
     arguments: T.List[str]
     output: T.List[str]
-    depfile: bool
+    depfile: T.Optional[str]
     capture:  bool
     depends: T.List[T.Union[build.BuildTarget, build.CustomTarget]]
 

mesonbuild/interpreter/type_checking.py

@@ -178,8 +178,8 @@ ENV_KW: KwargInfo[T.Union[EnvironmentVariables, T.List, T.Dict, str, None]] = Kw
     convertor=_env_convertor,
 )
 
-DEPFILE_KW = KwargInfo(
+DEPFILE_KW: KwargInfo[T.Optional[str]] = KwargInfo(
     'depfile',
-    str,
+    (str, type(None)),
     validator=lambda x: 'Depfile must be a plain filename with a subdirectory' if has_path_sep(x) else None
 )