Emit bundler-friendly URL locators

emcc.py

@@ -1206,8 +1206,6 @@ def phase_setup(state):
   else:
     target = 'a.out.js'
 
-  settings.TARGET_BASENAME = unsuffixed_basename(target)
-
   if settings.EXTRA_EXPORTED_RUNTIME_METHODS:
     diagnostics.warning('deprecated', 'EXTRA_EXPORTED_RUNTIME_METHODS is deprecated, please use EXPORTED_RUNTIME_METHODS instead')
     settings.EXPORTED_RUNTIME_METHODS += settings.EXTRA_EXPORTED_RUNTIME_METHODS
@@ -2399,6 +2397,13 @@ def phase_post_link(options, in_wasm, wasm_target, target):
   if options.oformat != OFormat.WASM:
     final_js = in_temp(target_basename + '.js')
 
+  settings.TARGET_BASENAME = unsuffixed_basename(target)
+
+  if options.oformat in (OFormat.JS, OFormat.MJS):
+    settings.TARGET_JS_NAME = target
+  else:
+    settings.TARGET_JS_NAME = get_secondary_target(target, '.js')
+
   if settings.MEM_INIT_IN_WASM:
     memfile = None
   else:
@@ -2534,6 +2539,15 @@ def phase_final_emitting(options, target, wasm_target, memfile):
     shared.JS.handle_license(final_js)
     shared.run_process([shared.PYTHON, shared.path_from_root('tools', 'hacky_postprocess_around_closure_limitations.py'), final_js])
 
+  # Unmangle previously mangled `import.meta` references in both main code and libraries.
+  # See also: `preprocess` in parseTools.js.
+  if settings.EXPORT_ES6 and settings.USE_ES6_IMPORT_META:
+    src = open(final_js).read()
+    final_js += '.esmeta.js'
+    with open(final_js, 'w') as f:
+      f.write(src.replace('EMSCRIPTEN$IMPORT$META', 'import.meta'))
+    save_intermediate('es6-import-meta')
+
   # Apply pre and postjs files
   if options.extern_pre_js or options.extern_post_js:
     logger.debug('applying extern pre/postjses')
@@ -2547,10 +2561,7 @@ def phase_final_emitting(options, target, wasm_target, memfile):
 
   shared.JS.handle_license(final_js)
 
-  if options.oformat in (OFormat.JS, OFormat.MJS):
-    js_target = target
-  else:
-    js_target = get_secondary_target(target, '.js')
+  js_target = settings.TARGET_JS_NAME
 
   # The JS is now final. Move it to its final location
   move_file(final_js, js_target)

src/closure-externs/closure-externs.js

@@ -11,6 +11,9 @@
  * The closure_compiler() method in tools/shared.py refers to this file when calling closure.
  */
 
+// Special placeholder for `import.meta`.
+var EMSCRIPTEN$IMPORT$META;
+
 // Closure externs used by library_sockfs.js
 
 /**

src/library_pthread.js

@@ -442,7 +442,11 @@ var LibraryPThread = {
         // it could load up the same file. In that case, developer must either deliver the Blob
         // object in Module['mainScriptUrlOrBlob'], or a URL to it, so that pthread Workers can
         // independently load up the same main application file.
-        'urlOrBlob': Module['mainScriptUrlOrBlob'] || _scriptDir,
+        'urlOrBlob': Module['mainScriptUrlOrBlob']
+#if !EXPORT_ES6
+        || _scriptDir
+#endif
+        ,
 #if WASM2JS
         // the polyfill WebAssembly.Memory instance has function properties,
         // which will fail in postMessage, so just send a custom object with the
@@ -469,6 +473,17 @@ var LibraryPThread = {
 #if MINIMAL_RUNTIME
       var pthreadMainJs = Module['worker'];
 #else
+#if EXPORT_ES6 && USE_ES6_IMPORT_META
+      // If we're using module output and there's no explicit override, use bundler-friendly pattern.
+      if (!Module['locateFile']) {
+#if PTHREADS_DEBUG
+        out('Allocating a new web worker from ' + new URL('{{{ PTHREAD_WORKER_FILE }}}', import.meta.url));
+#endif
+        // Use bundler-friendly `new Worker(new URL(..., import.meta.url))` pattern; works in browsers too.
+        PThread.unusedWorkers.push(new Worker(new URL('{{{ PTHREAD_WORKER_FILE }}}', import.meta.url)));
+        return;
+      }
+#endif
       // Allow HTML module to configure the location where the 'worker.js' file will be loaded from,
       // via Module.locateFile() function. If not specified, then the default URL 'worker.js' relative
       // to the main html file is loaded.

src/parseTools.js

@@ -33,6 +33,14 @@ function processMacros(text) {
 // Param filenameHint can be passed as a description to identify the file that is being processed, used
 // to locate errors for reporting and for html files to stop expansion between <style> and </style>.
 function preprocess(text, filenameHint) {
+  if (EXPORT_ES6 && USE_ES6_IMPORT_META) {
+    // `eval`, Terser and Closure don't support module syntax; to allow it,
+    // we need to temporarily replace `import.meta` usages with placeholders
+    // during preprocess phase, and back after all the other ops.
+    // See also: `phase_final_emitting` in emcc.py.
+    text = text.replace(/\bimport\.meta\b/g, 'EMSCRIPTEN$IMPORT$META');
+  }
+
   const IGNORE = 0;
   const SHOW = 1;
   // This state is entered after we have shown one of the block of an if/elif/else sequence.

src/preamble.js

@@ -746,10 +746,15 @@ function instrumentWasmTableWithAbort() {
 }
 #endif
 
+#if EXPORT_ES6
+// Use bundler-friendly `new URL(..., import.meta.url)` pattern; works in browsers too.
+var wasmBinaryFile = new URL('{{{ WASM_BINARY_FILE }}}', import.meta.url).toString();
+#else
 var wasmBinaryFile = '{{{ WASM_BINARY_FILE }}}';
 if (!isDataURI(wasmBinaryFile)) {
   wasmBinaryFile = locateFile(wasmBinaryFile);
 }
+#endif
 
 function getBinary(file) {
   try {
@@ -809,7 +814,7 @@ function getBinaryPromise() {
     }
 #endif
   }
-    
+
   // Otherwise, getBinary should be able to get it synchronously
   return Promise.resolve().then(function() { return getBinary(wasmBinaryFile); });
 }

src/settings_internal.js

@@ -32,6 +32,9 @@ var SIDE_MODULE_IMPORTS = [];
 // stores the base name of the output file (-o TARGET_BASENAME.js)
 var TARGET_BASENAME = '';
 
+// stores the base name (with extension) of the output JS file
+var TARGET_JS_NAME = '';
+
 // Indicates that the syscalls (which we see statically) indicate that they need
 // full filesystem support. Otherwise, when just a small subset are used, we can
 // get away without including the full filesystem - in particular, if open() is

src/worker.js

@@ -168,7 +168,7 @@ self.onmessage = function(e) {
 #endif
 
 #if MODULARIZE && EXPORT_ES6
-      import(e.data.urlOrBlob).then(function({{{ EXPORT_NAME }}}) {
+      (e.data.urlOrBlob ? import(e.data.urlOrBlob) : import('./{{{ TARGET_JS_NAME }}}')).then(function({{{ EXPORT_NAME }}}) {
         return {{{ EXPORT_NAME }}}.default(Module);
       }).then(function(instance) {
         Module = instance;