[test] Add skipExecIf which just skips the running of the test

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.skipExec = 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.skipExec:
+      self.skipTest('skipping test execution: ' + self.skipExec)
     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.skipExec = 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):