Remove use of addAtMain is webidl_binder.py (#14585)

Support for `addAtMain` in application without a main function was
removed in #13901 but I missed that fact that webidl_binder.py was doing
this.

This change replaces `addAtMain` with `addOnInit` and also makes the use
of `addAtMain` in applications without a `main` into an error so that
the problem (and solution) should be clear.

Update webidl binder test to only use sync compilation when needed, so
that code in question actually gets tested.

This change also reduces code size by not including `addAtMain` at all
in applications without a `main`.

Fixes: #14583.

src/parseTools.js

@@ -1083,6 +1083,7 @@ function addAtInit(code) {
 global.ATMAINS = [];
 
 function addAtMain(code) {
+  assert(HAS_MAIN, 'addAtMain called but program has no main function');
   ATMAINS.push(code);
 }
 

src/preamble.js

@@ -350,7 +350,9 @@ assert(INITIAL_MEMORY == {{{INITIAL_MEMORY}}}, 'Detected runtime INITIAL_MEMORY
 
 var __ATPRERUN__  = []; // functions called before the runtime is initialized
 var __ATINIT__    = []; // functions called during startup
+#if HAS_MAIN
 var __ATMAIN__    = []; // functions called when main() is to be run
+#endif
 var __ATEXIT__    = []; // functions called during shutdown
 var __ATPOSTRUN__ = []; // functions called after the main() is called
 
@@ -464,9 +466,11 @@ function addOnInit(cb) {
   __ATINIT__.unshift(cb);
 }
 
+#if HAS_MAIN
 function addOnPreMain(cb) {
   __ATMAIN__.unshift(cb);
 }
+#endif
 
 function addOnExit(cb) {
 #if EXIT_RUNTIME

tests/test_core.py

@@ -6944,6 +6944,7 @@ someweirdtext
     self.do_run(src, '418\ndotest returned: 42\n')
 
   @parameterized({
+    '': (None, False),
     'all': ('ALL', False),
     'fast': ('FAST', False),
     'default': ('DEFAULT', False),
@@ -6955,6 +6956,8 @@ someweirdtext
     if self.maybe_closure():
       # avoid closure minified names competing with our test code in the global name space
       self.set_setting('MODULARIZE')
+    else:
+      self.set_setting('WASM_ASYNC_COMPILATION', 0)
 
     # Force IDL checks mode
     with env_modify({'IDL_CHECKS': mode}):
@@ -6982,8 +6985,10 @@ someweirdtext
     if allow_memory_growth:
       self.set_setting('ALLOW_MEMORY_GROWTH')
 
-    output = test_file('webidl/output_%s.txt' % mode)
-    self.do_run_from_file(test_file('webidl/test.cpp'), output)
+    if not mode:
+      mode = 'DEFAULT'
+    expected = test_file('webidl/output_%s.txt' % mode)
+    self.do_run_from_file(test_file('webidl/test.cpp'), expected)
 
   ### Tests for tools
 

tests/webidl/post.js

@@ -149,14 +149,14 @@ console.log(TheModule.enum_value1);
 console.log(TheModule.enum_value2);
 
 // Enums from classes are accessed via the class.
-enumClassInstance = new TheModule.EnumClass();
+var enumClassInstance = new TheModule.EnumClass();
 console.log([enumClassInstance.GetEnum(), TheModule.EnumClass.e_val].join(','));
 
 // Enums from namespaces are accessed via the top-level module, as with classes defined
 // in namespaces, see `Inner` above.
 console.log(TheModule.e_namespace_val);
 
-typeTester = new TheModule.TypeTestClass();
+var typeTester = new TheModule.TypeTestClass();
 
 console.log('return char ' + (typeTester.ReturnCharMethod() & 255));
 typeTester.AcceptCharMethod((2<<6)-1);
@@ -288,4 +288,4 @@ if (isMemoryGrowthAllowed) {
 //
 
 console.log('\ndone.')
-})();
+})();

tools/webidl_binder.py

@@ -807,7 +807,7 @@ if len(deferred_js):
     %s
   }
   if (runtimeInitialized) setupEnums();
-  else addOnPreMain(setupEnums);
+  else addOnInit(setupEnums);
 })();
 ''' % '\n    '.join(deferred_js)]