[test] Add skipExecIf which just skips the running of the test (#21499

)

This means that even in CI when we might skip certain tests for graphics
or sounds we still get some assurance that the test code compiles.

test/common.py

@@ -863,6 +863,7 @@ def setUp(self):
     super().setUp()
     self.js_engines = config.JS_ENGINES.copy()
     self.settings_mods = {}
+    self.skip_exec = None
     self.emcc_args = ['-Wclosure', '-Werror', '-Wno-limited-postlink-optimizations']
     # TODO(https://github.com/emscripten-core/emscripten/issues/11121)
     # For historical reasons emcc compiles and links as C++ by default.
@@ -1967,6 +1968,8 @@ def assert_out_queue_empty(self, who):
   def run_browser(self, html_file, expected=None, message=None, timeout=None, extra_tries=1):
     if not has_browser():
       return
+    if self.skip_exec:
+      self.skipTest('skipping test execution: ' + self.skip_exec)
     if BrowserCore.unresponsive_tests >= BrowserCore.MAX_UNRESPONSIVE_TESTS:
       self.skipTest('too many unresponsive tests, skipping remaining tests')
     self.assert_out_queue_empty('previous test')

test/test_browser.py

@@ -187,9 +187,24 @@ def decorated(self, *args, **kwargs):
   return decorated
 
 
-requires_graphics_hardware = unittest.skipIf(os.getenv('EMTEST_LACKS_GRAPHICS_HARDWARE'), "This test requires graphics hardware")
-requires_sound_hardware = unittest.skipIf(os.getenv('EMTEST_LACKS_SOUND_HARDWARE'), "This test requires sound hardware")
-requires_offscreen_canvas = unittest.skipIf(os.getenv('EMTEST_LACKS_OFFSCREEN_CANVAS'), "This test requires a browser with OffscreenCanvas")
+def skipExecIf(cond, message):
+  def decorator(f):
+    assert callable(f)
+
+    @wraps(f)
+    def decorated(self, *args, **kwargs):
+      if cond:
+        self.skip_exec = message
+      f(self, *args, **kwargs)
+
+    return decorated
+
+  return decorator
+
+
+requires_graphics_hardware = skipExecIf(os.getenv('EMTEST_LACKS_GRAPHICS_HARDWARE'), 'This test requires graphics hardware')
+requires_sound_hardware = skipExecIf(os.getenv('EMTEST_LACKS_SOUND_HARDWARE'), 'This test requires sound hardware')
+requires_offscreen_canvas = skipExecIf(os.getenv('EMTEST_LACKS_OFFSCREEN_CANVAS'), 'This test requires a browser with OffscreenCanvas')
 
 
 class browser(BrowserCore):