Add cc.preprocess() method for c-like compilers

This introduce a new type of BuildTarget: CompileTarget. From ninja
backend POV it is the same thing as any other build target, except that
it skips the final link step. It could be used in the future for
transpilers too.

1 files changed, 40 insertions, 3 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index bf87071..14cc235 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -2581,6 +2581,44 @@ class CustomTarget(Target, CommandBase):
     def __len__(self) -> int:
         return len(self.outputs)
 
+class CompileTarget(BuildTarget):
+    '''
+    Target that only compile sources without linking them together.
+    It can be used as preprocessor, or transpiler.
+    '''
+
+    typename = 'compile'
+
+    def __init__(self,
+                 name: str,
+                 subdir: str,
+                 subproject: str,
+                 environment: environment.Environment,
+                 sources: T.List[File],
+                 output_templ: str,
+                 compiler: Compiler,
+                 kwargs):
+        compilers = {compiler.get_language(): compiler}
+        super().__init__(name, subdir, subproject, compiler.for_machine,
+                         sources, None, [], environment, compilers, kwargs)
+        self.filename = name
+        self.compiler = compiler
+        self.output_templ = output_templ
+        self.outputs = []
+        for f in sources:
+            plainname = os.path.basename(f.fname)
+            basename = os.path.splitext(plainname)[0]
+            self.outputs.append(output_templ.replace('@BASENAME@', basename).replace('@PLAINNAME@', plainname))
+        self.sources_map = dict(zip(sources, self.outputs))
+
+    def type_suffix(self) -> str:
+        return "@compile"
+
+    @property
+    def is_unity(self) -> bool:
+        return False
+
+
 class RunTarget(Target, CommandBase):
 
     typename = 'run'
@@ -2705,7 +2743,7 @@ class CustomTargetIndex(HoldableObject):
 
     typename: T.ClassVar[str] = 'custom'
 
-    target: CustomTarget
+    target: T.Union[CustomTarget, CompileTarget]
     output: str
 
     def __post_init__(self) -> None:
@@ -2716,8 +2754,7 @@ class CustomTargetIndex(HoldableObject):
         return f'{self.target.name}[{self.output}]'
 
     def __repr__(self):
-        return '<CustomTargetIndex: {!r}[{}]>'.format(
-            self.target, self.target.get_outputs().index(self.output))
+        return '<CustomTargetIndex: {!r}[{}]>'.format(self.target, self.output)
 
     def get_outputs(self) -> T.List[str]:
         return [self.output]