interpreter: Handle BuildTarget.vala_args as Files in the interpreter

Way back in Meson 0.25, support was added to `vala_args` for Files.
Strangely, this was never added to any other language, though it's been
discussed before. For type safety, it makes more sense to handle this in
the interpreter level, and pass only strings into the build IR.

This is accomplished by adding a `depend_files` field to the
`BuildTarget` class (which is not exposed to the user), and adding the
depend files into that field, while converting the arguments to relative
string paths. This ensures both the proper build dependencies happen, as
well as that the arguments are always strings.

docs/yaml/functions/_build_target_base.yaml

@@ -48,6 +48,11 @@ kwargs:
       compiler flags to use for the given language;
       eg: `cpp_args` for C++
 
+  vala_args:
+    type: list[str | file]
+    description: |
+      Compiler flags for Vala. Unlike other languages this may contain Files
+
   sources:
     type: str | file | custom_tgt | custom_idx | generated_list | structured_src
     description: Additional source files. Same as the source varargs.

mesonbuild/backend/backends.py

@@ -1475,7 +1475,7 @@ def get_custom_target_sources(self, target: build.CustomTarget) -> T.List[str]:
             srcs += fname
         return srcs
 
-    def get_custom_target_depend_files(self, target: build.CustomTarget, absolute_paths: bool = False) -> T.List[str]:
+    def get_target_depend_files(self, target: T.Union[build.CustomTarget, build.BuildTarget], absolute_paths: bool = False) -> T.List[str]:
         deps: T.List[str] = []
         for i in target.depend_files:
             if isinstance(i, mesonlib.File):

mesonbuild/backend/ninjabackend.py

@@ -1151,7 +1151,7 @@ def generate_custom_target(self, target: build.CustomTarget):
         self.custom_target_generator_inputs(target)
         (srcs, ofilenames, cmd) = self.eval_custom_target_command(target)
         deps = self.unwrap_dep_list(target)
-        deps += self.get_custom_target_depend_files(target)
+        deps += self.get_target_depend_files(target)
         if target.build_always_stale:
             deps.append('PHONY')
         if target.depfile is None:
@@ -1214,7 +1214,7 @@ def generate_run_target(self, target: build.RunTarget):
             elem.add_item('description', f'Running external command {target.name}{cmd_type}')
             elem.add_item('pool', 'console')
         deps = self.unwrap_dep_list(target)
-        deps += self.get_custom_target_depend_files(target)
+        deps += self.get_target_depend_files(target)
         elem.add_dep(deps)
         self.add_build(elem)
         self.processed_targets.add(target.get_id())
@@ -1712,18 +1712,10 @@ def generate_vala_compile(self, target: build.BuildTarget) -> \
             if isinstance(gensrc, modules.GResourceTarget):
                 gres_xml, = self.get_custom_target_sources(gensrc)
                 args += ['--gresources=' + gres_xml]
-        extra_args = []
-
-        for a in target.extra_args.get('vala', []):
-            if isinstance(a, File):
-                relname = a.rel_to_builddir(self.build_to_src)
-                extra_dep_files.append(relname)
-                extra_args.append(relname)
-            else:
-                extra_args.append(a)
         dependency_vapis = self.determine_dep_vapis(target)
         extra_dep_files += dependency_vapis
-        args += extra_args
+        extra_dep_files.extend(self.get_target_depend_files(target))
+        args += target.get_extra_args('vala')
         element = NinjaBuildElement(self.all_outputs, valac_outputs,
                                     self.compiler_to_rule_name(valac),
                                     all_files + dependency_vapis)
@@ -2622,7 +2614,7 @@ def generate_genlist_for_target(self, genlist: build.GeneratedList, target: buil
         exe = generator.get_exe()
         infilelist = genlist.get_inputs()
         outfilelist = genlist.get_outputs()
-        extra_dependencies = self.get_custom_target_depend_files(genlist)
+        extra_dependencies = self.get_target_depend_files(genlist)
         for i, curfile in enumerate(infilelist):
             if len(generator.outputs) == 1:
                 sole_output = os.path.join(self.get_target_private_dir(target), outfilelist[i])

mesonbuild/backend/vs2010backend.py

@@ -187,7 +187,7 @@ def generate_genlist_for_target(self, genlist: T.Union[build.GeneratedList, buil
                 else:
                     sole_output = ''
                 infilename = os.path.join(down, curfile.rel_to_builddir(self.build_to_src, target_private_dir))
-                deps = self.get_custom_target_depend_files(genlist, True)
+                deps = self.get_target_depend_files(genlist, True)
                 base_args = generator.get_arglist(infilename)
                 outfiles_rel = genlist.get_outputs_for(curfile)
                 outfiles = [os.path.join(target_private_dir, of) for of in outfiles_rel]
@@ -699,7 +699,7 @@ def gen_run_target_vcxproj(self, target: build.RunTarget, ofname: str, guid: str
         (root, type_config) = self.create_basic_project(target.name,
                                                         temp_dir=target.get_id(),
                                                         guid=guid)
-        depend_files = self.get_custom_target_depend_files(target)
+        depend_files = self.get_target_depend_files(target)
 
         if not target.command:
             # This is an alias target and thus doesn't run any command. It's
@@ -738,7 +738,7 @@ def gen_custom_target_vcxproj(self, target: build.CustomTarget, ofname: str, gui
         # from the target dir, not the build root.
         target.absolute_paths = True
         (srcs, ofilenames, cmd) = self.eval_custom_target_command(target, True)
-        depend_files = self.get_custom_target_depend_files(target, True)
+        depend_files = self.get_target_depend_files(target, True)
         # Always use a wrapper because MSBuild eats random characters when
         # there are many arguments.
         tdir_abs = os.path.join(self.environment.get_build_dir(), self.get_target_dir(target))

mesonbuild/build.py

@@ -735,6 +735,7 @@ def __init__(
         self.link_language = kwargs.get('link_language')
         self.link_targets: T.List[LibTypes] = []
         self.link_whole_targets: T.List[T.Union[StaticLibrary, CustomTarget, CustomTargetIndex]] = []
+        self.depend_files: T.List[File] = []
         self.link_depends = []
         self.added_deps = set()
         self.name_prefix_set = False
@@ -746,7 +747,7 @@ 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.Dict[str, T.List[str]] = {}
         self.sources: T.List[File] = []
         self.generated: T.List['GeneratedTypes'] = []
         self.extra_files: T.List[File] = []
@@ -1278,7 +1279,7 @@ def get_debug_filename(self) -> T.Optional[str]:
     def get_outputs(self) -> T.List[str]:
         return self.outputs
 
-    def get_extra_args(self, language):
+    def get_extra_args(self, language) -> T.List[str]:
         return self.extra_args.get(language, [])
 
     @lru_cache(maxsize=None)

mesonbuild/interpreter/interpreter.py

@@ -3230,6 +3230,46 @@ def build_library(self, node, args, kwargs):
         else:
             raise InterpreterException(f'Unknown default_library value: {default_library}.')
 
+    def __convert_file_args(self, raw: T.List[mesonlib.FileOrString], allow_file: bool) -> T.Tuple[T.List[mesonlib.File], T.List[str]]:
+        """Convert raw target arguments from File | str to File.
+
+        This removes files from the command line and replaces them with string
+        values, but adds the files to depends list
+
+        :param raw: the raw arguments
+        :return: A tuple of file dependencies and raw arguments
+        """
+        depend_files: T.List[mesonlib.File] = []
+        args: T.List[str] = []
+        build_to_source = mesonlib.relpath(self.environment.get_source_dir(),
+                                           self.environment.get_build_dir())
+
+        for a in raw:
+            if isinstance(a, mesonlib.File):
+                if not allow_file:
+                    raise InvalidArguments('File type arguments are only allowed for vala')
+                depend_files.append(a)
+                args.append(a.rel_to_builddir(build_to_source))
+            else:
+                args.append(a)
+
+        return depend_files, args
+
+    def __process_language_args(self, 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.
+        """
+        d = kwargs.setdefault('depend_files', [])
+
+        for l in compilers.all_languages:
+            deps, args = self.__convert_file_args(kwargs[f'{l}_args'], l == 'vala')
+            kwargs[f'{l}_args'] = args
+            d.extend(deps)
+
     @T.overload
     def build_target(self, node: mparser.BaseNode, args: T.Tuple[str, SourcesVarargsType],
                      kwargs: kwtypes.Executable, targetclass: T.Type[build.Executable]) -> build.Executable: ...
@@ -3295,6 +3335,7 @@ 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.__process_language_args(kwargs)
 
         # Filter out kwargs from other target types. For example 'soversion'
         # passed to library() when default_library == 'static'.

mesonbuild/interpreter/kwargs.py

@@ -7,7 +7,7 @@
 
 import typing as T
 
-from typing_extensions import TypedDict, Literal, Protocol
+from typing_extensions import TypedDict, Literal, Protocol, NotRequired
 
 from .. import build
 from .. import coredata
@@ -326,6 +326,7 @@ class _BaseBuildTarget(TypedDict):
     """
 
     override_options: T.Dict[OptionKey, T.Union[str, int, bool, T.List[str]]]
+    depend_files: NotRequired[T.List[File]]
 
 
 class _BuildTarget(_BaseBuildTarget):