ninja: Fix header deps of generated source compiles

Because we were iterating over all generated sources of a target in one
go, we weren't adding the correct header_deps for generated source
compiles. We need to aggregate the header_deps first before generating
source compile targets for generated source files.

mesonbuild/backend/ninjabackend.py

@@ -270,18 +270,25 @@ int dummy;
         unity_src = []
         unity_deps = [] # Generated sources that must be built before compiling a Unity target.
         header_deps += self.get_generated_headers(target)
-        generator_output_sources = [] # Needed to determine the linker
+
+        # Get a list of all generated *sources* (sources files, headers,
+        # objects, etc). Needed to determine the linker.
+        generated_output_sources = [] 
+        # Get a list of all generated headers that will be needed while building
+        # this target's sources (generated sources and pre-existing sources).
+        # This will be set as dependencies of all the target's sources. At the
+        # same time, also deal with generated sources that need to be compiled.
+        generated_source_files = []
         for gensource in target.get_generated_sources():
             if isinstance(gensource, build.CustomTarget):
                 for src in gensource.output:
                     src = os.path.join(self.get_target_dir(gensource), src)
-                    generator_output_sources.append(src)
+                    generated_output_sources.append(src)
                     if self.environment.is_source(src) and not self.environment.is_header(src):
                         if is_unity:
                             unity_deps.append(os.path.join(self.environment.get_build_dir(), RawFilename(src)))
                         else:
-                            obj_list.append(self.generate_single_compile(target, outfile, RawFilename(src), True,
-                                                                         header_deps))
+                            generated_source_files.append(RawFilename(src))
                     elif self.environment.is_object(src):
                         obj_list.append(src)
                     elif self.environment.is_library(src):
@@ -293,7 +300,7 @@ int dummy;
                         header_deps.append(RawFilename(src))
             else:
                 for src in gensource.get_outfilelist():
-                    generator_output_sources.append(src)
+                    generated_output_sources.append(src)
                     if self.environment.is_object(src):
                         obj_list.append(os.path.join(self.get_target_private_dir(target), src))
                     elif not self.environment.is_header(src):
@@ -306,8 +313,15 @@ int dummy;
                             abs_src = os.path.join(self.environment.get_build_dir(), rel_src)
                             unity_src.append(abs_src)
                         else:
-                            obj_list.append(self.generate_single_compile(target, outfile, src, True,
-                                                                         header_deps=header_deps))
+                            generated_source_files.append(src)
+        # These are the generated source files that need to be built for use by
+        # this target. We create the Ninja build file elements for this here
+        # because we need `header_deps` to be fully generated in the above loop.
+        for src in generated_source_files:
+            obj_list.append(self.generate_single_compile(target, outfile, src, True,
+                                                         header_deps=header_deps))
+        # Generate compilation targets for sources belonging to this target that
+        # are generated by other rules (this is only used for Vala right now)
         src_list = []
         for src in gen_src_deps:
             src_list.append(src)
@@ -324,6 +338,7 @@ int dummy;
                     header_deps.append(src)
                 else:
                     obj_list.append(self.generate_single_compile(target, outfile, src, True, [], header_deps))
+        # Generate compile targets for all the pre-existing sources for this target
         for src in target.get_sources():
             if src.endswith('.vala'):
                 continue
@@ -339,7 +354,7 @@ int dummy;
         if is_unity:
             for src in self.generate_unity_files(target, unity_src):
                 obj_list.append(self.generate_single_compile(target, outfile, src, True, unity_deps + header_deps))
-        linker = self.determine_linker(target, src_list + generator_output_sources)
+        linker = self.determine_linker(target, src_list + generated_output_sources)
         elem = self.generate_link(target, outfile, outname, obj_list, linker, pch_objects)
         self.generate_shlib_aliases(target, self.get_target_dir(target))
         elem.write(outfile)