compiler.preprocess: add depends kwarg

This patch adds 'depends' keyword to compiler.preprocess().
It allows to execute other targets before doing the preprocessing.
Test-case is added to demonstrate that functionality: it
generates the header before preprocessing the C source that
uses that generated header.

Thanks to @bruchar1 for getting this patch to work.

docs/markdown/snippets/preprocess-depends.md

@@ -0,0 +1,5 @@
+## `depends` kwarg now supported by compiler.preprocess()
+
+It is now possible to specify the dependent targets with `depends:`
+for compiler.preprocess(). These targets should be built before the
+preprocessing starts.

docs/yaml/objects/compiler.yaml

@@ -681,3 +681,10 @@ methods:
       type: dep | list[dep]
       description: Additionally dependencies required.
       since: 1.1.0
+    depends:
+      type: list[build_tgt | custom_tgt]
+      description: |
+        Specifies that this target depends on the specified
+        target(s). These targets should be built before starting
+        to preprocess an input.
+      since: 1.4.0

mesonbuild/backend/backends.py

@@ -2012,7 +2012,9 @@ class Backend:
     def compiler_to_generator(self, target: build.BuildTarget,
                               compiler: 'Compiler',
                               sources: _ALL_SOURCES_TYPE,
-                              output_templ: str) -> build.GeneratedList:
+                              output_templ: str,
+                              depends: T.Optional[T.List[T.Union[build.BuildTarget, build.CustomTarget, build.CustomTargetIndex]]] = None,
+                              ) -> build.GeneratedList:
         '''
         Some backends don't support custom compilers. This is a convenience
         method to convert a Compiler to a Generator.
@@ -2027,9 +2029,12 @@ class Backend:
         commands += compiler.get_compile_only_args() + ['@INPUT@']
         commands += self.get_source_dir_include_args(target, compiler)
         commands += self.get_build_dir_include_args(target, compiler)
-        generator = build.Generator(exe, args + commands.to_native(), [output_templ], depfile='@PLAINNAME@.d')
+        generator = build.Generator(exe, args + commands.to_native(),
+                                    [output_templ], depfile='@PLAINNAME@.d',
+                                    depends=depends)
         return generator.process_files(sources, self.interpreter)
 
     def compile_target_to_generator(self, target: build.CompileTarget) -> build.GeneratedList:
         all_sources = T.cast('_ALL_SOURCES_TYPE', target.sources) + T.cast('_ALL_SOURCES_TYPE', target.generated)
-        return self.compiler_to_generator(target, target.compiler, all_sources, target.output_templ)
+        return self.compiler_to_generator(target, target.compiler, all_sources,
+                                          target.output_templ, target.depends)

mesonbuild/backend/ninjabackend.py

@@ -718,6 +718,8 @@ class NinjaBackend(backends.Backend):
         for dep in itertools.chain(target.link_targets, target.link_whole_targets):
             if isinstance(dep, (build.StaticLibrary, build.SharedLibrary)):
                 header_deps += self.get_generated_headers(dep)
+        if isinstance(target, build.CompileTarget):
+            header_deps.extend(target.get_generated_headers())
         target.cached_generated_headers = header_deps
         return header_deps
 

mesonbuild/build.py

@@ -1763,12 +1763,12 @@ class Generator(HoldableObject):
                  *,
                  depfile: T.Optional[str] = None,
                  capture: bool = False,
-                 depends: T.Optional[T.List[T.Union[BuildTarget, 'CustomTarget']]] = None,
+                 depends: T.Optional[T.List[T.Union[BuildTarget, 'CustomTarget', 'CustomTargetIndex']]] = None,
                  name: str = 'Generator'):
         self.exe = exe
         self.depfile = depfile
         self.capture = capture
-        self.depends: T.List[T.Union[BuildTarget, 'CustomTarget']] = depends or []
+        self.depends: T.List[T.Union[BuildTarget, 'CustomTarget', 'CustomTargetIndex']] = depends or []
         self.arglist = arguments
         self.outputs = output
         self.name = name
@@ -2763,7 +2763,8 @@ class CompileTarget(BuildTarget):
                  backend: Backend,
                  compile_args: T.List[str],
                  include_directories: T.List[IncludeDirs],
-                 dependencies: T.List[dependencies.Dependency]):
+                 dependencies: T.List[dependencies.Dependency],
+                 depends: T.List[T.Union[BuildTarget, CustomTarget, CustomTargetIndex]]):
         compilers = {compiler.get_language(): compiler}
         kwargs = {
             'build_by_default': False,
@@ -2778,6 +2779,7 @@ class CompileTarget(BuildTarget):
         self.output_templ = output_templ
         self.outputs = []
         self.sources_map: T.Dict[File, str] = {}
+        self.depends = list(depends or [])
         for f in self.sources:
             self._add_output(f)
         for gensrc in self.generated:
@@ -2799,6 +2801,11 @@ class CompileTarget(BuildTarget):
         self.outputs.append(o)
         self.sources_map[f] = o
 
+    def get_generated_headers(self) -> T.List[File]:
+        gen_headers: T.List[File] = []
+        for dep in self.depends:
+            gen_headers += [File(True, dep.subdir, o) for o in dep.get_outputs()]
+        return gen_headers
 
 class RunTarget(Target, CommandBase):
 

mesonbuild/interpreter/compiler.py

@@ -96,6 +96,7 @@ if T.TYPE_CHECKING:
         compile_args: T.List[str]
         include_directories: T.List[build.IncludeDirs]
         dependencies: T.List[dependencies.Dependency]
+        depends: T.List[T.Union[build.BuildTarget, build.CustomTarget, build.CustomTargetIndex]]
 
 
 class _TestMode(enum.Enum):
@@ -148,6 +149,12 @@ _DEPENDENCIES_KW: KwargInfo[T.List['dependencies.Dependency']] = KwargInfo(
     listify=True,
     default=[],
 )
+_DEPENDS_KW: KwargInfo[T.List[T.Union[build.BuildTarget, build.CustomTarget, build.CustomTargetIndex]]] = KwargInfo(
+    'depends',
+    ContainerTypeInfo(list, (build.BuildTarget, build.CustomTarget, build.CustomTargetIndex)),
+    listify=True,
+    default=[],
+)
 _INCLUDE_DIRS_KW: KwargInfo[T.List[build.IncludeDirs]] = KwargInfo(
     'include_directories',
     ContainerTypeInfo(list, build.IncludeDirs),
@@ -853,6 +860,7 @@ class CompilerHolder(ObjectHolder['Compiler']):
         KwargInfo('compile_args', ContainerTypeInfo(list, str), listify=True, default=[]),
         _INCLUDE_DIRS_KW,
         _DEPENDENCIES_KW.evolve(since='1.1.0'),
+        _DEPENDS_KW.evolve(since='1.4.0'),
     )
     def preprocess_method(self, args: T.Tuple[T.List['mesonlib.FileOrString']], kwargs: 'PreprocessKW') -> T.List[build.CustomTargetIndex]:
         compiler = self.compiler.get_preprocessor()
@@ -878,7 +886,8 @@ class CompilerHolder(ObjectHolder['Compiler']):
             self.interpreter.backend,
             kwargs['compile_args'],
             kwargs['include_directories'],
-            kwargs['dependencies'])
+            kwargs['dependencies'],
+            kwargs['depends'])
         self.interpreter.add_target(tg.name, tg)
         # Expose this target as list of its outputs, so user can pass them to
         # other targets, list outputs, etc.

test cases/common/259 preprocess/meson.build

@@ -13,9 +13,14 @@ bar_x = custom_target(
   capture: true,
 )
 
+foo_h = import('fs').copyfile('foo.x', 'foo.h')
+
 dep = declare_dependency(compile_args: '-DPLOP=0')
 
-pp_files = cc.preprocess('foo.c', bar_x, 'math.c', output: '@PLAINNAME@.c', dependencies: dep)
+pp_files = cc.preprocess('foo.c', bar_x, 'math.c',
+  output: '@PLAINNAME@.c',
+  dependencies: dep,
+  depends: foo_h)
 
 foreach f : pp_files
   message(f.full_path())