From 8561f1b4b340934806d07fdd7db039d126508667 Mon Sep 17 00:00:00 2001
From: "Alon Zakai (kripken)" <alonzakai@gmail.com>
Date: Thu, 29 Oct 2020 20:03:21 -0700
Subject: [PATCH 1/2] fix

---
 ChangeLog.md        |  4 ++++
 emcc.py             |  4 +++-
 src/settings.js     |  4 ++++
 tests/test_other.py | 25 +++++++++++++++++++++++++
 4 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 2445c88135f99..da5bd0e3055af 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -35,6 +35,10 @@ Current Trunk
   modules.  As one side effect of this change it is now required that JavaScript
   functions that are imported by address are now required to have a `__sig`
   specified in the library JavaScript file.
+- `MODULARIZE` + `WASM_ASYNC_COMPILATION=0`, that is, modularize mode but with
+  async compilation turned off, so that startup is synchronous, now returns the
+  Module object from the factory function (as it would not make sense to return
+  a Promise without async startup). See #12647
 
 2.0.8: 10/24/2020
 -----------------
diff --git a/emcc.py b/emcc.py
index 120f3f563822d..64440cf6e81cb 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2841,7 +2841,9 @@ def modularize():
   logger.debug('Modularizing, assigning to var ' + shared.Settings.EXPORT_NAME)
   src = open(final_js).read()
 
-  return_value = shared.Settings.EXPORT_NAME + '.ready'
+  return_value = shared.Settings.EXPORT_NAME
+  if shared.Settings.WASM_ASYNC_COMPILATION:
+    return_value += '.ready'
   if not shared.Settings.EXPORT_READY_PROMISE:
     return_value = '{}'
 
diff --git a/src/settings.js b/src/settings.js
index e7f8e0a271068..6899ea3dc140d 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -954,6 +954,10 @@ var DETERMINISTIC = 0;
 // resolved with the module instance when it is safe to run the compiled code,
 // similar to the `onRuntimeInitialized` callback. You do not need to use the
 // `onRuntimeInitialized` callback when using `MODULARIZE`.
+//
+// (If WASM_ASYNC_COMPILATION is off, that is, if compilation is
+// *synchronous*, then it would not make sense to return a Promise, and instead
+// the Module object itself is returned, which is ready to be used.)
 // 
 // The default name of the function is `Module`, but can be changed using the
 // `EXPORT_NAME` option. We recommend renaming it to a more typical name for a
diff --git a/tests/test_other.py b/tests/test_other.py
index 4396c1b716768..c3a3980cd8753 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -4838,6 +4838,31 @@ def test_EXPORT_NAME_with_html(self):
     self.assertNotEqual(result.returncode, 0)
     self.assertContained('Customizing EXPORT_NAME requires that the HTML be customized to use that name', result.stdout)
 
+  def test_modularize_sync_compilation(self):
+    create_test_file('post.js', r'''
+console.log('before');
+var result = Module();
+// It should be an object.
+console.log(typeof result);
+// And it should have the exports that Module has, showing it is Module in fact.
+console.log(typeof result._main);
+// And it should not be a Promise.
+console.log(typeof result.then);
+console.log('after');
+''')
+    self.run_process([EMCC, path_from_root('tests', 'hello_world.c'),
+                      '-s', 'MODULARIZE=1',
+                      '-s', 'WASM_ASYNC_COMPILATION=0',
+                      '--extern-post-js', 'post.js'])
+    self.assertContained('''\
+before
+hello, world!
+object
+function
+undefined
+after
+''', self.run_js('a.out.js'))
+
   def test_export_all_3142(self):
     create_test_file('src.cpp', r'''
 typedef unsigned int Bit32u;

From 9e4cf4fd79cd0d28f358868fbe1241972c72a0db Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Fri, 30 Oct 2020 10:18:22 -0700
Subject: [PATCH 2/2] Fix existing test

---
 tests/test_browser.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_browser.py b/tests/test_browser.py
index 2f58aa70d459e..14d74f50aa9c7 100644
--- a/tests/test_browser.py
+++ b/tests/test_browser.py
@@ -3274,7 +3274,7 @@ def test_modularize(self):
         src = open(path_from_root('tests', 'browser_test_hello_world.c')).read()
         create_test_file('test.c', self.with_report_result(src))
         # this test is synchronous, so avoid async startup due to wasm features
-        self.compile_btest(['test.c', '-s', 'MODULARIZE=1', '-s', 'WASM_ASYNC_COMPILATION=0', '-s', 'SINGLE_FILE=1'] + args + opts)
+        self.compile_btest(['test.c', '-s', 'MODULARIZE=1', '-s', 'SINGLE_FILE=1'] + args + opts)
         create_test_file('a.html', '''
           <script src="a.out.js"></script>
           <script>