build: Use typed_kwargs for language args

This also moves the repacking into the interpreter, making the build
implementation simpler and removing a layering violation. This also
makes use a defaultdict to remove the need to call `.get()`

docs/yaml/functions/_build_target_base.yaml

@@ -43,7 +43,7 @@ kwargs:
     description: precompiled header file to use for the given language
 
   <lang>_args:
-    type: list[str]
+    type: list[str | file]
     description: |
       compiler flags to use for the given language;
       eg: `cpp_args` for C++

mesonbuild/backend/ninjabackend.py

@@ -1068,7 +1068,7 @@ def should_use_dyndeps_for_target(self, target: 'build.BuildTarget') -> bool:
             return True
         if 'cpp' not in target.compilers:
             return False
-        if '-fmodules-ts' in target.extra_args.get('cpp', []):
+        if '-fmodules-ts' in target.extra_args['cpp']:
             return True
         # Currently only the preview version of Visual Studio is supported.
         cpp = target.compilers['cpp']
@@ -1462,7 +1462,7 @@ def generate_cs_target(self, target: build.BuildTarget):
         compiler = target.compilers['cs']
         rel_srcs = [os.path.normpath(s.rel_to_builddir(self.build_to_src)) for s in src_list]
         deps = []
-        commands = compiler.compiler_args(target.extra_args.get('cs', []))
+        commands = compiler.compiler_args(target.extra_args['cs'])
         commands += compiler.get_buildtype_args(buildtype)
         commands += compiler.get_optimization_args(target.get_option(OptionKey('optimization')))
         commands += compiler.get_debug_args(target.get_option(OptionKey('debug')))
@@ -1718,7 +1718,7 @@ def generate_vala_compile(self, target: build.BuildTarget) -> \
                 args += ['--gresources=' + gres_xml]
         extra_args = []
 
-        for a in target.extra_args.get('vala', []):
+        for a in target.extra_args['vala']:
             if isinstance(a, File):
                 relname = a.rel_to_builddir(self.build_to_src)
                 extra_dep_files.append(relname)

mesonbuild/build.py

@@ -720,7 +720,7 @@ def __init__(
             objects: T.List[ObjectTypes],
             environment: environment.Environment,
             compilers: T.Dict[str, 'Compiler'],
-            kwargs):
+            kwargs: T.Dict[str, T.Any]):
         super().__init__(name, subdir, subproject, True, for_machine, environment, install=kwargs.get('install', False))
         self.all_compilers = compilers
         self.compilers = OrderedDict() # type: OrderedDict[str, Compiler]
@@ -740,7 +740,7 @@ def __init__(
         # as Vala which generates .vapi and .h besides the compiled output.
         self.outputs = [self.filename]
         self.pch: T.Dict[str, T.List[str]] = {}
-        self.extra_args: T.Dict[str, T.List['FileOrString']] = {}
+        self.extra_args: T.DefaultDict[str, T.List[FileOrString]] = kwargs.get('language_args', defaultdict(list))
         self.sources: T.List[File] = []
         self.generated: T.List['GeneratedTypes'] = []
         self.extra_files: T.List[File] = []
@@ -818,6 +818,8 @@ def check_unknown_kwargs(self, kwargs):
     def check_unknown_kwargs_int(self, kwargs, known_kwargs):
         unknowns = []
         for k in kwargs:
+            if k == 'language_args':
+                continue
             if k not in known_kwargs:
                 unknowns.append(k)
         if len(unknowns) > 0:
@@ -1091,10 +1093,6 @@ def process_kwargs(self, kwargs):
         self.process_kwargs_base(kwargs)
         self.original_kwargs = kwargs
 
-        for lang in all_languages:
-            lang_args = extract_as_list(kwargs, f'{lang}_args')
-            self.add_compiler_args(lang, lang_args)
-
         self.add_pch('c', extract_as_list(kwargs, 'c_pch'))
         self.add_pch('cpp', extract_as_list(kwargs, 'cpp_pch'))
 
@@ -1273,8 +1271,8 @@ def get_filename(self) -> str:
     def get_outputs(self) -> T.List[str]:
         return self.outputs
 
-    def get_extra_args(self, language):
-        return self.extra_args.get(language, [])
+    def get_extra_args(self, language: str) -> T.List[FileOrString]:
+        return self.extra_args[language]
 
     @lru_cache(maxsize=None)
     def get_dependencies(self) -> OrderedSet[Target]:
@@ -1529,16 +1527,6 @@ def add_include_dirs(self, args: T.Sequence['IncludeDirs'], set_is_system: T.Opt
             ids = [IncludeDirs(x.get_curdir(), x.get_incdirs(), is_system, x.get_extra_build_dirs()) for x in ids]
         self.include_dirs += ids
 
-    def add_compiler_args(self, language: str, args: T.List['FileOrString']) -> None:
-        args = listify(args)
-        for a in args:
-            if not isinstance(a, (str, File)):
-                raise InvalidArguments('A non-string passed to compiler args.')
-        if language in self.extra_args:
-            self.extra_args[language] += args
-        else:
-            self.extra_args[language] = args
-
     def get_aliases(self) -> T.List[T.Tuple[str, str, str]]:
         return []
 
@@ -2788,6 +2776,7 @@ def __init__(self,
         compilers = {compiler.get_language(): compiler}
         kwargs = {
             'build_by_default': False,
+
             f'{compiler.language}_args': compile_args,
             'include_directories': include_directories,
             'dependencies': dependencies,
@@ -2905,7 +2894,7 @@ def __init__(self, name: str, subdir: str, subproject: str, for_machine: Machine
             raise InvalidArguments('structured sources are not supported in Java targets.')
         self.filename = self.name + '.jar'
         self.outputs = [self.filename]
-        self.java_args = kwargs.get('java_args', [])
+        self.java_args = self.extra_args['java']
         self.main_class = kwargs.get('main_class', '')
         self.java_resources: T.Optional[StructuredSources] = kwargs.get('java_resources', None)
 

mesonbuild/interpreter/interpreter.py

@@ -3204,10 +3204,26 @@ def build_library(self, node, args, kwargs):
         else:
             raise InterpreterException(f'Unknown default_library value: {default_library}.')
 
+    @staticmethod
+    def __extract_language_args(kwargs: T.Dict[str, T.List[mesonlib.FileOrString]]) -> None:
+        """Convert split language args into a combined dictionary.
+
+        The Meson DSL takes arguments in the form `<lang>_args : args`, but in the
+        build layer we store these in a single dictionary as `{<lang>: args}`.
+        This function extracts the arguments from the DSL format and prepares
+        them for the IR.
+        """
+        args: T.DefaultDict[str, T.List[mesonlib.FileOrString]] = collections.defaultdict(list)
+        for l in compilers.all_languages:
+            # We need to a copy here because the receiving code assumes that it
+            # owns the language_args, and without the copy in `both_library` we can
+            # end up with two classes that think they own these
+            args[l] = kwargs[f'{l}_args'].copy()
+        kwargs['language_args'] = args
+
     def build_target(self, node: mparser.BaseNode, args, kwargs, targetclass):
         @FeatureNewKwargs('build target', '1.2.0', ['rust_dependency_map'])
         @FeatureNewKwargs('build target', '0.42.0', ['rust_crate_type', 'build_rpath', 'implicit_include_directories'])
-        @FeatureNewKwargs('build target', '0.41.0', ['rust_args'])
         @FeatureNewKwargs('build target', '0.38.0', ['build_by_default'])
         @FeatureNewKwargs('build target', '0.48.0', ['gnu_symbol_visibility'])
         def build_target_decorator_caller(self, node, args, kwargs):
@@ -3243,10 +3259,11 @@ def build_target_decorator_caller(self, node, args, kwargs):
             mlog.debug('Unknown target type:', str(targetclass))
             raise RuntimeError('Unreachable code')
         self.kwarg_strings_to_includedirs(kwargs)
+        self.__extract_language_args(kwargs)
 
         # Filter out kwargs from other target types. For example 'soversion'
         # passed to library() when default_library == 'static'.
-        kwargs = {k: v for k, v in kwargs.items() if k in targetclass.known_kwargs}
+        kwargs = {k: v for k, v in kwargs.items() if k in targetclass.known_kwargs | {'language_args'}}
 
         srcs: T.List['SourceInputs'] = []
         struct: T.Optional[build.StructuredSources] = build.StructuredSources()

mesonbuild/interpreter/type_checking.py

@@ -480,8 +480,16 @@ def link_whole_validator(values: T.List[T.Union[StaticLibrary, CustomTarget, Cus
     KwargInfo('verbose', bool, default=False, since='0.62.0'),
 ]
 
+_LANGUAGE_KWS: T.List[KwargInfo[T.List[str]]] = [
+    KwargInfo(f'{lang}_args', ContainerTypeInfo(list, (str, File)), listify=True, default=[])
+    for lang in compilers.all_languages - {'rust'}
+]
+_LANGUAGE_KWS.append(KwargInfo(
+    'rust_args', ContainerTypeInfo(list, str), listify=True, default=[], since='0.41.0'))
+
 # Applies to all build_target like classes
 _ALL_TARGET_KWS: T.List[KwargInfo] = [
+    *_LANGUAGE_KWS,
     OVERRIDE_OPTIONS_KW,
 ]
 

mesonbuild/modules/rust.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from __future__ import annotations
-
 import os
 import typing as T
 
@@ -156,12 +155,14 @@ def test(self, state: ModuleState, args: T.Tuple[str, BuildTarget], kwargs: Func
         new_target_kwargs = base_target.original_kwargs.copy()
         # Don't mutate the shallow copied list, instead replace it with a new
         # one
-        new_target_kwargs['rust_args'] = \
-            new_target_kwargs.get('rust_args', []) + kwargs['rust_args'] + ['--test']
         new_target_kwargs['install'] = False
         new_target_kwargs['dependencies'] = new_target_kwargs.get('dependencies', []) + kwargs['dependencies']
         new_target_kwargs['link_with'] = new_target_kwargs.get('link_with', []) + kwargs['link_with']
 
+        lang_args = base_target.extra_args.copy()
+        lang_args['rust'] = base_target.extra_args['rust'] + kwargs['rust_args'] + ['--test']
+        new_target_kwargs['language_args'] = lang_args
+
         sources = T.cast('T.List[SourceOutputs]', base_target.sources.copy())
         sources.extend(base_target.generated)