Add support for opaque build targets. Closes #10627.biggen

2 files changed, 22 insertions, 4 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 8943464..68efb3d 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -131,6 +131,7 @@ class InstallData:
         self.symlinks: T.List[InstallSymlinkData] = []
         self.install_scripts: T.List[ExecutableSerialisation] = []
         self.install_subdirs: T.List[SubdirInstallData] = []
+        self.install_opaque: T.List[(str, str)] = []
 
 @dataclass(eq=False)
 class TargetInstallData:
@@ -1510,6 +1511,7 @@ class Backend:
         self.generate_symlink_install(d)
         self.generate_custom_install_script(d)
         self.generate_subdir_install(d)
+        self.generate_opaque_install(d)
         return d
 
     def create_install_data_files(self) -> None:
@@ -1637,6 +1639,11 @@ class Backend:
                                               tag=tag)
                         d.targets.append(i)
             elif isinstance(t, build.CustomTarget):
+                if t.is_opaque:
+                    # The contents of opaque dirs are installed in a separate function.
+                    # The "output" of this target is the stampfile and we do not want
+                    # to install that.
+                    continue
                 # If only one install_dir is specified, assume that all
                 # outputs will be installed into it. This is for
                 # backwards-compatibility and because it makes sense to
@@ -1771,6 +1778,15 @@ class Backend:
             i = SubdirInstallData(src_dir, dst_dir, dst_name, sd.install_mode, sd.exclude, sd.subproject, sd.install_tag)
             d.install_subdirs.append(i)
 
+    def generate_opaque_install(self, d: InstallData) -> None:
+        for ct in self.build.get_targets().values():
+            if isinstance(ct, build.CustomTarget) and ct.is_opaque:
+                opdata = mesonlib.get_opaque_data(ct.subproject, ct.name)
+                if len(ct.install_dir) !=1:
+                    raise RuntimeError('Internal error, install_dir must have only one string.')
+                installdir = ct.install_dir[0]
+                d.install_opaque.append((opdata.out, installdir))
+
     def get_introspection_data(self, target_id: str, target: build.Target) -> T.List['TargetIntrospectionData']:
         '''
         Returns a list of source dicts with the following format for a given target:
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 593c201..8377dcf 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -3445,15 +3445,17 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         # empty. https://github.com/mesonbuild/meson/issues/1220
         ctlist = []
         for t in self.build.get_targets().values():
-            if isinstance(t, build.CustomTarget):
+            if isinstance(t, build.CustomTarget) and not t.is_opaque:
                 # Create a list of all custom target outputs
                 for o in t.get_outputs():
                     ctlist.append(os.path.join(self.get_target_dir(t), o))
         # As above, but restore the top level directory after deletion.
+        gendir_list = []
         for t in self.build.get_targets().values():
-            if isinstance(t, build.CustomTarget):
-                if False:
-                    gendir_list.append('fake')
+            if isinstance(t, build.CustomTarget) and t.is_opaque:
+                opdata = mesonlib.get_opaque_data(t.subproject, t.name)
+                gendir_list.append(opdata.scratch)
+                gendir_list.append(opdata.out)
 
         if ctlist or gendir_list:
             elem.add_dep(self.generate_custom_target_clean(ctlist, gendir_list))