Skip compilation when no tests match filter

docs/news.d/1157.feature.rst

@@ -0,0 +1 @@
+Compilation is now skipped when no tests match the active filters (e.g. ``--with-attributes``), avoiding unnecessary work when no tests would run.

tests/unit/test_ui.py

@@ -650,6 +650,31 @@ def check_stdout(ui, expected):
         setup(ui)
         check_stdout(ui, "lib.tb_filter.Test 1\n" "Listed 1 tests")
 
+    @with_tempdir
+    def test_skips_compilation_when_no_matching_tests(self, tempdir):
+        """
+        Test that compilation is skipped when attribute filtering results in
+        no matching tests, e.g. --with-attributes=.nonexistent
+        """
+        ui = self._create_ui("--with-attributes", ".nonexistent", "--no-color")
+        lib = ui.add_library("lib")
+        file_name = str(Path(tempdir) / "tb_skip.vhd")
+        create_vhdl_test_bench_file(
+                "tb_skip",
+                file_name,
+                tests=["Test 1"],
+            )
+        lib.add_source_file(file_name)
+
+        post_run = mock.Mock()
+        with mock.patch("sys.stdout", autospec=True) as stdout:
+            with mock.patch.object(ui, "_compile") as compile_mock:
+                self._run_main(ui, post_run=post_run)
+                compile_mock.assert_not_called()
+        text = "".join([call[1][0] for call in stdout.write.mock_calls])
+        self.assertEqual(set(text.splitlines()), {"No tests were run!"})
+        self.assertTrue(post_run.called)
+
     @with_tempdir
     def test_export_json(self, tempdir):
         tdir = Path(tempdir)

vunit/ui/__init__.py

@@ -1041,6 +1041,10 @@ def _main_run(self, post_run):
         if self._args.changed:
             test_list = self._get_test_list_depending_on_change(test_list)
 
+        if test_list.num_tests == 0:
+            LOGGER.info("Skipping compilation: no matching tests after filtering.")
+            return self._main_run_report(post_run, simulator_if)
+
         self._compile(simulator_if)
         print()
 
@@ -1057,6 +1061,15 @@ def _main_run(self, post_run):
 
         report.set_real_total_time(ostools.get_time() - start_time)
         self._update_test_history(report, simulator_if)
+        return self._main_run_report(post_run, simulator_if, report)
+
+    def _main_run_report(self, post_run, simulator_if, report=None):
+        """
+        Print report and handle post_run callback and xunit XML output.
+        """
+        if report is None:
+            report = TestReport(printer=self._printer)
+
         report.print_str()
 
         if post_run is not None: