backend/ninja: Extend InlcudeDirs.rel_string_list for backend use

This adds the ability to remove build directories that don't exist.

This doesn't require a second call to reverse() because that was being
used to switch the order of the build and src directories, but
`rel_string_list` returns them in the expected order already.

mesonbuild/backend/ninjabackend.py

@@ -3009,26 +3009,15 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         return (rel_obj, rel_src)
 
     @lru_cache(maxsize=None)
-    def generate_inc_dir(self, compiler: 'Compiler', d: str, basedir: str, is_system: bool) -> \
-            T.Tuple['ImmutableListProtocol[str]', 'ImmutableListProtocol[str]']:
-        # Avoid superfluous '/.' at the end of paths when d is '.'
-        if d not in ('', '.'):
-            expdir = os.path.normpath(os.path.join(basedir, d))
-        else:
-            expdir = basedir
-        srctreedir = os.path.normpath(os.path.join(self.build_to_src, expdir))
-        sargs = compiler.get_include_args(srctreedir, is_system)
-        # There may be include dirs where a build directory has not been
-        # created for some source dir. For example if someone does this:
-        #
-        # inc = include_directories('foo/bar/baz')
-        #
-        # But never subdir()s into the actual dir.
-        if os.path.isdir(os.path.join(self.environment.get_build_dir(), expdir)):
-            bargs = compiler.get_include_args(expdir, is_system)
-        else:
-            bargs = []
-        return (sargs, bargs)
+    def generate_inc_dir(self, compiler: 'Compiler', inc: build.IncludeDirs
+                         ) -> ImmutableListProtocol[str]:
+        # We should iterate include dirs in reversed orders because
+        # -Ipath will add to begin of array. And without reverse
+        # flags will be added in reversed order.
+        args: T.List[str] = []
+        for p in inc.rel_string_list(self.build_to_src, self.build_dir):
+            args.extend(compiler.get_include_args(p, inc.is_system))
+        return args
 
     def _generate_single_compile(self, target: build.BuildTarget, compiler: Compiler) -> CompilerArgs:
         commands = self._generate_single_compile_base_args(target, compiler)
@@ -3067,17 +3056,10 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         # external deps and must maintain the order in which they are specified.
         # Hence, we must reverse the list so that the order is preserved.
         for i in reversed(target.get_include_dirs()):
-            basedir = i.curdir
             # We should iterate include dirs in reversed orders because
             # -Ipath will add to begin of array. And without reverse
             # flags will be added in reversed order.
-            for d in reversed(i.incdirs):
-                # Add source subdir first so that the build subdir overrides it
-                (compile_obj, includeargs) = self.generate_inc_dir(compiler, d, basedir, i.is_system)
-                commands += compile_obj
-                commands += includeargs
-            for d in i.extra_build_dirs:
-                commands += compiler.get_include_args(d, i.is_system)
+            commands += self.generate_inc_dir(compiler, i)
         # Add per-target compile args, f.ex, `c_args : ['-DFOO']`. We set these
         # near the end since these are supposed to override everything else.
         commands += self.escape_extra_args(target.get_extra_args(compiler.get_language()))

mesonbuild/build.py

@@ -509,10 +509,12 @@ class IncludeDirs(HoldableObject):
             strlist.append(os.path.join(builddir, self.curdir, idir))
         return strlist
 
-    def rel_string_list(self, build_to_src: str) -> T.List[str]:
+    def rel_string_list(self, build_to_src: str, build_root: T.Optional[str] = None) -> T.List[str]:
         """Convert IncludeDirs object to a list of relative string paths.
 
         :param build_to_src: The relative path from the build dir to source dir
+        :param build_root: The absolute build root. When provided, build
+            directories that have not been created will be ignored. Default: None.
         :return: A list if strings (without compiler argument)
         """
         strlist: T.List[str] = []
@@ -523,9 +525,11 @@ class IncludeDirs(HoldableObject):
                     expdir = bld_dir
                 else:
                     expdir = self.curdir
-                strlist.append(bld_dir)
+                if build_root is None or os.path.isdir(os.path.join(build_root, expdir)):
+                    strlist.append(bld_dir)
                 if add_src:
                     strlist.append(os.path.normpath(os.path.join(build_to_src, expdir)))
+
         return strlist