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])
+```

mesonbuild/build.py

@@ -2383,9 +2383,9 @@ def process_kwargs(self, kwargs):
             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, '

mesonbuild/interpreter/kwargs.py

@@ -338,19 +338,19 @@ class StaticLibrary(_BuildTarget):
 
 class SharedLibrary(_BuildTarget):
 
-    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget]]
+    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class SharedModule(_BuildTarget):
 
-    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget]]
+    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class Library(_BuildTarget):
 
     """For library, both_library, and as a base for build_target"""
 
-    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget]]
+    vs_module_def: T.Optional[T.Union[str, File, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class BuildTarget(Library):

mesonbuild/interpreter/type_checking.py

@@ -481,9 +481,10 @@ def link_whole_validator(values: T.List[T.Union[StaticLibrary, CustomTarget, Cus
     KwargInfo('verbose', bool, default=False, since='0.62.0'),
 ]
 
-_VS_MODULE_DEF_KW: KwargInfo[T.Union[str, File, CustomTarget]] = KwargInfo(
+_VS_MODULE_DEF_KW: KwargInfo[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])