fix using a CustomTargetIndex for vs_module_defs

Because `CustomTargetIndex`es don't have a `subdir` property, but they do
implement the `get_subdir()` method

docs/markdown/snippets/vs_module_defs_customtargetindex.md

@@ -0,0 +1,8 @@
+## vs_module_defs keyword now supports indexes of custom_target
+
+This means you can do something like:
+```meson
+defs = custom_target('generate_module_defs', ...)
+shared_library('lib1', vs_module_defs : defs[0])
+shared_library('lib2', vs_module_defs : defs[2])
+```

docs/yaml/functions/shared_library.yaml

@@ -45,6 +45,8 @@ kwargs:
       Specify a Microsoft module definition file for controlling symbol exports,
       etc., on platforms where that is possible (e.g. Windows).
 
+      *(Since 1.3.0)* [[@custom_idx]] are supported
+
   rust_abi:
     type: str
     since: 1.3.0

docs/yaml/functions/shared_module.yaml

@@ -40,6 +40,8 @@ kwargs:
       Specify a Microsoft module definition file for controlling symbol exports,
       etc., on platforms where that is possible (e.g. Windows).
 
+      *(Since 1.3.0)* [[@custom_idx]] are supported
+
   rust_abi:
     type: str
     since: 1.3.0

mesonbuild/build.py

@@ -2331,13 +2331,13 @@ class SharedLibrary(BuildTarget):
             elif isinstance(path, File):
                 # When passing a generated file.
                 self.vs_module_defs = path
-            elif isinstance(path, CustomTarget):
+            elif isinstance(path, (CustomTarget, CustomTargetIndex)):
                 # When passing output of a Custom Target
-                self.vs_module_defs = File.from_built_file(path.subdir, path.get_filename())
+                self.vs_module_defs = File.from_built_file(path.get_subdir(), path.get_filename())
             else:
                 raise InvalidArguments(
                     'Shared library vs_module_defs must be either a string, '
-                    'a file object or a Custom Target')
+                    'a file object, a Custom Target, or a Custom Target Index')
             self.process_link_depends(path)
 
         rust_abi = kwargs.get('rust_abi')

mesonbuild/interpreter/kwargs.py

@@ -359,7 +359,7 @@ class _SharedLibMixin(TypedDict):
     darwin_versions: T.Optional[T.Tuple[str, str]]
     soversion: T.Optional[str]
     version: T.Optional[str]
-    vs_module_defs: T.Optional[T.Union[str, File, build.CustomTarget]]
+    vs_module_defs: T.Optional[T.Union[str, File, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class SharedLibrary(_BuildTarget, _SharedLibMixin, _LibraryMixin):
@@ -368,7 +368,7 @@ class SharedLibrary(_BuildTarget, _SharedLibMixin, _LibraryMixin):
 
 class SharedModule(_BuildTarget, _LibraryMixin):
 
-    vs_module_defs: T.Optional[T.Union[str, File, build.CustomTarget]]
+    vs_module_defs: T.Optional[T.Union[str, File, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class Library(_BuildTarget, _SharedLibMixin, _StaticLibMixin, _LibraryMixin):

mesonbuild/interpreter/type_checking.py

@@ -513,9 +513,10 @@ RUST_ABI_KW: KwargInfo[T.Union[str, None]] = KwargInfo(
     since='1.3.0',
     validator=in_set_validator({'rust', 'c'}))
 
-_VS_MODULE_DEFS_KW: KwargInfo[T.Optional[T.Union[str, File, CustomTarget]]] = KwargInfo(
+_VS_MODULE_DEFS_KW: KwargInfo[T.Optional[T.Union[str, File, CustomTarget, CustomTargetIndex]]] = KwargInfo(
     'vs_module_defs',
-    (str, File, CustomTarget, NoneType),
+    (str, File, CustomTarget, CustomTargetIndex, NoneType),
+    since_values={CustomTargetIndex: '1.3.0'}
 )
 
 # Applies to all build_target like classes

test cases/windows/10 vs module defs generated custom target/subdir/meson.build

@@ -5,3 +5,5 @@ def_file = custom_target('gen_def',
         output: 'somedll.def')
 
 shlib = shared_library('somedll', 'somedll.c', vs_module_defs: def_file)
+
+shared_library('somedll2', 'somedll.c', vs_module_defs: def_file[0])