Enable SINGLE_FILE + PTHREADS html output (emscripten-core#22547)

In SINGLE_FILE mode, the JS is inlined directly into the generated HTML.
However for pthreads builds we need to be able to create workers that
use the same inlined JS. To enable this we encode the JS file into a
data URL that can be used for the script `src` attribute. The pthread
worker can then use this `src`.

Prior to this change using SINGLE_FILE + PTHREADS + html output would
simply fail.

Author: sbc100

test/test_browser.py

@@ -3693,11 +3693,17 @@ def test_pthread_gcc_spinlock(self):
     '': ([],),
     'O3': (['-O3'],),
     'minimal_runtime': (['-sMINIMAL_RUNTIME'],),
+    'single_file': (['-sSINGLE_FILE'],),
   })
   def test_pthread_create(self, args):
     self.btest_exit('pthread/test_pthread_create.c',
                     args=['-pthread', '-sPTHREAD_POOL_SIZE=8'] + args,
                     extra_tries=0) # this should be 100% deterministic
+    files = os.listdir('.')
+    if '-sSINGLE_FILE' in args:
+      self.assertEqual(len(files), 1, files)
+    else:
+      self.assertEqual(len(files), 4, files)
 
   # Test that preallocating worker threads work.
   def test_pthread_preallocates_workers(self):

tools/link.py

@@ -2079,7 +2079,7 @@ def phase_final_emitting(options, state, target, wasm_target):
     return
 
   target_dir = os.path.dirname(os.path.abspath(target))
-  if settings.PTHREADS and not settings.STRICT:
+  if settings.PTHREADS and not settings.STRICT and not settings.SINGLE_FILE:
     worker_file = shared.replace_suffix(target, get_worker_js_suffix())
     write_file(worker_file, '''\
 // This file is no longer used by emscripten and has been created as a placeholder
@@ -2535,14 +2535,19 @@ def generate_traditional_runtime_html(target, options, js_target, target_basenam
     # Normal code generation path
     script.src = base_js_target
 
-  # inline script for SINGLE_FILE output
   if settings.SINGLE_FILE:
-    js_contents = script.inline or ''
-    if script.src:
-      js_contents += read_file(js_target)
+    # In SINGLE_FILE mode we either inline the script, or in the case
+    # of SHARED_MEMORY convert the entire thing into a data URL.
+    if settings.SHARED_MEMORY:
+      assert not script.inline
+      script.src = get_subresource_location(js_target)
+    else:
+      js_contents = script.inline or ''
+      if script.src:
+        js_contents += read_file(js_target)
+      script.src = None
+      script.inline = read_file(js_target)
     delete_file(js_target)
-    script.src = None
-    script.inline = js_contents
   else:
     if not settings.WASM_ASYNC_COMPILATION:
       # We need to load the wasm file before anything else, since it
@@ -2819,16 +2824,21 @@ def replacement(self):
     """Returns the script tag to replace the {{{ SCRIPT }}} tag in the target"""
     assert (self.src or self.inline) and not (self.src and self.inline)
     if self.src:
-      quoted_src = quote(self.src)
+      src = self.src
+      if src.startswith('data:'):
+        filename = src
+      else:
+        src = quote(self.src)
+        filename = f'./{src}'
       if settings.EXPORT_ES6:
         return f'''
         <script type="module">
-          import initModule from "./{quoted_src}";
+          import initModule from "{filename}";
           initModule(Module);
         </script>
         '''
       else:
-        return f'<script async type="text/javascript" src="{quoted_src}"></script>'
+        return f'<script async type="text/javascript" src="{src}"></script>'
     else:
       return '<script>\n%s\n</script>' % self.inline