ninjabackend: Fix get_target_generated_sources() return type

Type annotation, documentation string, and implementation were doing 3
different things. Change implementation to match type annotation which
makes the most sense because it match what get_target_sources() does.

All callers only use keys from the returned dictionary any way, but
that's going to change in next commits.

mesonbuild/backend/ninjabackend.py

@@ -707,14 +707,14 @@ class NinjaBackend(backends.Backend):
     def get_target_generated_sources(self, target: build.BuildTarget) -> T.MutableMapping[str, File]:
         """
         Returns a dictionary with the keys being the path to the file
-        (relative to the build directory) of that type and the value
-        being the GeneratorList or CustomTarget that generated it.
+        (relative to the build directory) and the value being the File object
+        representing the same path.
         """
         srcs: T.MutableMapping[str, File] = OrderedDict()
         for gensrc in target.get_generated_sources():
             for s in gensrc.get_outputs():
-                f = self.get_target_generated_dir(target, gensrc, s)
-                srcs[f] = s
+                rel_src = self.get_target_generated_dir(target, gensrc, s)
+                srcs[rel_src] = File.from_built_relative(rel_src)
         return srcs
 
     def get_target_sources(self, target: build.BuildTarget) -> T.MutableMapping[str, File]:
@@ -881,8 +881,7 @@ class NinjaBackend(backends.Backend):
         # same time, also deal with generated sources that need to be compiled.
         generated_source_files = []
         for rel_src in generated_sources.keys():
-            dirpart, fnamepart = os.path.split(rel_src)
-            raw_src = File(True, dirpart, fnamepart)
+            raw_src = File.from_built_relative(rel_src)
             if self.environment.is_source(rel_src) and not self.environment.is_header(rel_src):
                 if is_unity and self.get_target_source_can_unity(target, rel_src):
                     unity_deps.append(raw_src)
@@ -943,8 +942,7 @@ class NinjaBackend(backends.Backend):
         # often contain duplicate symbols and will fail to compile properly
         vala_generated_source_files = []
         for src in transpiled_sources:
-            dirpart, fnamepart = os.path.split(src)
-            raw_src = File(True, dirpart, fnamepart)
+            raw_src = File.from_built_relative(src)
             # Generated targets are ordered deps because the must exist
             # before the sources compiling them are used. After the first
             # compile we get precise dependency info from dep files.
@@ -1327,8 +1325,7 @@ class NinjaBackend(backends.Backend):
         generated_sources = self.get_target_generated_sources(target)
         gen_src_list = []
         for rel_src in generated_sources.keys():
-            dirpart, fnamepart = os.path.split(rel_src)
-            raw_src = File(True, dirpart, fnamepart)
+            raw_src = File.from_built_relative(rel_src)
             if rel_src.endswith('.java'):
                 gen_src_list.append(raw_src)
 

mesonbuild/mesonlib/universal.py

@@ -418,6 +418,11 @@ class File(HoldableObject):
     def from_built_file(subdir: str, fname: str) -> 'File':
         return File(True, subdir, fname)
 
+    @staticmethod
+    def from_built_relative(relative: str) -> 'File':
+        dirpart, fnamepart = os.path.split(relative)
+        return File(True, dirpart, fnamepart)
+
     @staticmethod
     def from_absolute_file(fname: str) -> 'File':
         return File(False, '', fname)