pass all outputs of a custom_target as arguments to a test

Meson was passing only the first output and warning about it.  To do this
easily, refactor construct_target_rel_path to return a list.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/backend/backends.py

@@ -1143,13 +1143,8 @@ class Backend:
                     cmd_args.append(a)
                 elif isinstance(a, str):
                     cmd_args.append(a)
-                elif isinstance(a, build.Executable):
-                    p = self.construct_target_rel_path(a, t.workdir)
-                    if p == a.get_filename():
-                        p = './' + p
-                    cmd_args.append(p)
                 elif isinstance(a, build.Target):
-                    cmd_args.append(self.construct_target_rel_path(a, t.workdir))
+                    cmd_args.extend(self.construct_target_rel_paths(a, t.workdir))
                 else:
                     raise MesonException('Bad object in test command.')
             ts = TestSerialisation(t.get_name(), t.project_name, t.suite, cmd, is_cross,
@@ -1166,12 +1161,24 @@ class Backend:
     def write_test_serialisation(self, tests: T.List['Test'], datafile: T.BinaryIO) -> None:
         pickle.dump(self.create_test_serialisation(tests), datafile)
 
-    def construct_target_rel_path(self, a: build.Target, workdir: T.Optional[str]) -> str:
-        if workdir is None:
-            return self.get_target_filename(a)
+    def construct_target_rel_paths(self, t: build.Target, workdir: T.Optional[str]) -> T.List[str]:
+        target_dir = self.get_target_dir(t)
+        # ensure that test executables can be run when passed as arguments
+        if isinstance(t, build.Executable) and workdir is None:
+            target_dir = target_dir or '.'
+
+        if isinstance(t, build.BuildTarget):
+            outputs = [t.get_filename()]
+        else:
+            assert isinstance(t, build.CustomTarget)
+            outputs = t.get_outputs()
+
+        outputs = [os.path.join(target_dir, x) for x in outputs]
+        if workdir is not None:
             assert os.path.isabs(workdir)
-        abs_path = self.get_target_filename_abs(a)
-        return os.path.relpath(abs_path, workdir)
+            outputs = [os.path.join(self.environment.get_build_dir(), x) for x in outputs]
+            outputs = [os.path.relpath(x, workdir) for x in outputs]
+        return outputs
 
     def generate_depmf_install(self, d: InstallData) -> None:
         if self.build.dep_manifest_name is None:

test cases/common/245 custom target index source/main.c

@@ -1,6 +1,8 @@
+#include <assert.h>
 #include "gen.h"
 
-int main(void)
+int main(int argc)
 {
+  assert(argc == 3);
   return genfunc();
 }

test cases/common/245 custom target index source/meson.build

@@ -46,5 +46,6 @@ exe_together = executable('exe_together',
   install: false,
 )
 
-test('exe_separate', exe_separate)
-test('exe_together', exe_together)
+# also cover passing custom target to tests as arguments
+test('exe_separate', exe_separate, args: ['unused1', 'unused2'])
+test('exe_together', exe_together, args: gen)