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.

6 files changed, 55 insertions, 20 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index a8bf387f9..dd9e6ee6c 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -1475,7 +1475,7 @@ class Backend:
             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):
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 29883bac7..d4d4e2ff6 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -1151,7 +1151,7 @@ class NinjaBackend(backends.Backend):
         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 @@ class NinjaBackend(backends.Backend):
             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 @@ class NinjaBackend(backends.Backend):
             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 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         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])
diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index c9c21a135..b9ada532b 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -187,7 +187,7 @@ class Vs2010Backend(backends.Backend):
                 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 @@ class Vs2010Backend(backends.Backend):
         (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 @@ class Vs2010Backend(backends.Backend):
         # 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))
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 8208fa0d9..9f0abf539 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -735,6 +735,7 @@ class BuildTarget(Target):
         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 @@ class BuildTarget(Target):
         # 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 @@ class BuildTarget(Target):
     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)
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index 0b6ccef22..29eaed202 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -3230,6 +3230,46 @@ class Interpreter(InterpreterBase, HoldableObject):
         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 @@ class Interpreter(InterpreterBase, HoldableObject):
             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'.
diff --git a/mesonbuild/interpreter/kwargs.py b/mesonbuild/interpreter/kwargs.py
index 241a08b76..26ecb4ef9 100644
--- a/mesonbuild/interpreter/kwargs.py
+++ b/mesonbuild/interpreter/kwargs.py
@@ -7,7 +7,7 @@ from __future__ import annotations
 
 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):