allow RunTarget to skip wrapping due to env

Forcing serialization on when writing out the build rule makes very
little sense. It was always "forced" on because we mandated a couple of
environment variables due to legacy reasons.

Add an attribute to RunTarget to say that a given target doesn't *need*
those environment variables, and let ninja optimize them away and run
the command directly if set.

2 files changed, 10 insertions, 8 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 0f70643..b5b8171 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -1445,11 +1445,12 @@ class Backend:
 
     def get_run_target_env(self, target: build.RunTarget) -> build.EnvironmentVariables:
         env = target.env if target.env else build.EnvironmentVariables()
-        introspect_cmd = join_args(self.environment.get_build_command() + ['introspect'])
-        env.set('MESON_SOURCE_ROOT', [self.environment.get_source_dir()])
-        env.set('MESON_BUILD_ROOT', [self.environment.get_build_dir()])
-        env.set('MESON_SUBDIR', [target.subdir])
-        env.set('MESONINTROSPECT', [introspect_cmd])
+        if target.default_env:
+            introspect_cmd = join_args(self.environment.get_build_command() + ['introspect'])
+            env.set('MESON_SOURCE_ROOT', [self.environment.get_source_dir()])
+            env.set('MESON_BUILD_ROOT', [self.environment.get_build_dir()])
+            env.set('MESON_SUBDIR', [target.subdir])
+            env.set('MESONINTROSPECT', [introspect_cmd])
         return env
 
     def run_postconf_scripts(self) -> None:
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 422f6bc..8eb4901 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from __future__ import annotations
 
 from collections import OrderedDict
 from enum import Enum, unique
@@ -1034,7 +1035,7 @@ class NinjaBackend(backends.Backend):
             subproject_prefix = ''
         return f'{subproject_prefix}{target.name}'
 
-    def generate_run_target(self, target):
+    def generate_run_target(self, target: build.RunTarget):
         target_name = self.build_run_target_name(target)
         if not target.command:
             # This is an alias target, it has no command, it just depends on
@@ -1044,9 +1045,9 @@ class NinjaBackend(backends.Backend):
             target_env = self.get_run_target_env(target)
             _, _, cmd = self.eval_custom_target_command(target)
             meson_exe_cmd, reason = self.as_meson_exe_cmdline(target.command[0], cmd[1:],
-                                                              force_serialize=True, env=target_env,
+                                                              env=target_env,
                                                               verbose=True)
-            cmd_type = f' (wrapped by meson {reason})'
+            cmd_type = f' (wrapped by meson {reason})' if reason else ''
             internal_target_name = f'meson-{target_name}'
             elem = NinjaBuildElement(self.all_outputs, internal_target_name, 'CUSTOM_COMMAND', [])
             elem.add_item('COMMAND', meson_exe_cmd)