Remove USE_ES6_IMPORT_META setting

This setting was added (IIUC) as a temporary workaround for the lack or
support for `import.meta` in browser and tooling.

However `import.meta` has been at stage 4 for almost 5 years now:
tc39/proposal-import-meta#21

Webback (released in 2020) also has builtin support for `import.meta`,
so I would hope the use case for disabling this setting no longer
exists.

See #9234 and #8729

ChangeLog.md

@@ -20,6 +20,10 @@ See docs/process.md for more on how version tagging works.
 
 3.1.75 (in development)
 -----------------------
+- The `USE_ES6_IMPORT_META` settings was removed.  This setting was always
+  on by default, but now it cannot be disabled.  This setting was originally
+  added in 2019 as a temporary measuse while engines and bundlers learned to
+  deal with `import meta`. (#23171)
 
 3.1.74 - 12/14/24
 -----------------

site/source/docs/tools_reference/settings_reference.rst

@@ -1977,18 +1977,6 @@ This is implicitly enabled if the output suffix is set to 'mjs'.
 
 Default value: false
 
-.. _use_es6_import_meta:
-
-USE_ES6_IMPORT_META
-===================
-
-Use the ES6 Module relative import feature 'import.meta.url'
-to auto-detect WASM Module path.
-It might not be supported on old browsers / toolchains. This setting
-may not be disabled when Node.js is targeted (-sENVIRONMENT=*node*).
-
-Default value: true
-
 .. _export_name:
 
 EXPORT_NAME

src/library_pthread.js

@@ -412,7 +412,7 @@ var LibraryPThread = {
 #endif
 #endif
       };
-#if EXPORT_ES6 && USE_ES6_IMPORT_META
+#if EXPORT_ES6
       // If we're using module output, use bundler-friendly pattern.
 #if PTHREADS_DEBUG
       dbg(`Allocating a new web worker from ${import.meta.url}`);
@@ -434,7 +434,7 @@ var LibraryPThread = {
       // the first case in their bundling step. The latter ends up producing an invalid
       // URL to import from the server (e.g., for webpack the file:// path).
       worker = new Worker(new URL('{{{ TARGET_JS_NAME }}}', import.meta.url), workerOptions);
-#else
+#else // EXPORT_ES6
       var pthreadMainJs = _scriptName;
 #if expectToReceiveOnModule('mainScriptUrlOrBlob')
       // We can't use makeModuleReceiveWithVar here since we want to also
@@ -457,7 +457,7 @@ var LibraryPThread = {
       } else
 #endif
       worker = new Worker(pthreadMainJs, workerOptions);
-#endif // EXPORT_ES6 && USE_ES6_IMPORT_META
+#endif // EXPORT_ES6
       PThread.unusedWorkers.push(worker);
     },
 

src/parseTools.mjs

@@ -44,7 +44,7 @@ export function processMacros(text, filename) {
 // Also handles #include x.js (similar to C #include <file>)
 export function preprocess(filename) {
   let text = read(filename);
-  if (EXPORT_ES6 && USE_ES6_IMPORT_META) {
+  if (EXPORT_ES6) {
     // `eval`, Terser and Closure don't support module syntax; to allow it,
     // we need to temporarily replace `import.meta` and `await import` usages
     // with placeholders during preprocess phase, and back after all the other ops.

src/preamble.js

@@ -609,7 +609,7 @@ var wasmBinaryFile = '{{{ WASM_BINARY_FILE }}}';
 #else
 var wasmBinaryFile;
 function findWasmBinary() {
-#if EXPORT_ES6 && USE_ES6_IMPORT_META && !AUDIO_WORKLET
+#if EXPORT_ES6 && !AUDIO_WORKLET
   if (Module['locateFile']) {
 #endif
     var f = '{{{ WASM_BINARY_FILE }}}';
@@ -619,7 +619,7 @@ function findWasmBinary() {
     }
 #endif
     return f;
-#if EXPORT_ES6 && USE_ES6_IMPORT_META && !AUDIO_WORKLET // In single-file mode, repeating WASM_BINARY_FILE would emit the contents again. For an Audio Worklet, we cannot use `new URL()`.
+#if EXPORT_ES6 && !AUDIO_WORKLET // In single-file mode, repeating WASM_BINARY_FILE would emit the contents again. For an Audio Worklet, we cannot use `new URL()`.
   }
 #if ENVIRONMENT_MAY_BE_SHELL
   if (ENVIRONMENT_IS_SHELL)

src/settings.js

@@ -1353,13 +1353,6 @@ var MODULARIZE = false;
 // [link]
 var EXPORT_ES6 = false;
 
-// Use the ES6 Module relative import feature 'import.meta.url'
-// to auto-detect WASM Module path.
-// It might not be supported on old browsers / toolchains. This setting
-// may not be disabled when Node.js is targeted (-sENVIRONMENT=*node*).
-// [link]
-var USE_ES6_IMPORT_META = true;
-
 // Global variable to export the module as for environments without a
 // standardized module loading system (e.g. the browser and SM shell).
 // [link]
@@ -2267,4 +2260,5 @@ var LEGACY_SETTINGS = [
   ['MIN_IE_VERSION', [0x7FFFFFFF], 'No longer supported'],
   ['WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG', [0], 'No longer supported'],
   ['AUTO_ARCHIVE_INDEXES', [0, 1], 'No longer needed'],
+  ['USE_ES6_IMPORT_META', [1], 'Disabling is no longer supported'],
 ];

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-53980
+53979

test/other/test_unoptimized_code_size_no_asserts.js.size

@@ -1 +1 @@
-29400
+29399

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-52776
+52775

test/test_other.py

@@ -403,16 +403,6 @@ def test_emcc_output_mjs_closure(self):
     self.assertContained('new URL("hello_world.wasm", import.meta.url)', src)
     self.assertContained('hello, world!', self.run_js('hello_world.mjs'))
 
-  def test_emcc_output_mjs_web_no_import_meta(self):
-    # Ensure we don't emit import.meta.url at all for:
-    # ENVIRONMENT=web + EXPORT_ES6 + USE_ES6_IMPORT_META=0
-    self.run_process([EMCC, '-o', 'hello_world.mjs',
-                      test_file('hello_world.c'),
-                      '-sENVIRONMENT=web', '-sUSE_ES6_IMPORT_META=0'])
-    src = read_file('hello_world.mjs')
-    self.assertNotContained('import.meta.url', src)
-    self.assertContained('export default Module;', src)
-
   def test_export_es6_implies_modularize(self):
     self.run_process([EMCC, test_file('hello_world.c'), '-sEXPORT_ES6'])
     src = read_file('a.out.js')
@@ -422,11 +412,6 @@ def test_export_es6_requires_modularize(self):
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sEXPORT_ES6', '-sMODULARIZE=0'])
     self.assertContained('EXPORT_ES6 requires MODULARIZE to be set', err)
 
-  def test_export_es6_node_requires_import_meta(self):
-    err = self.expect_fail([EMCC, test_file('hello_world.c'),
-                            '-sENVIRONMENT=node', '-sEXPORT_ES6', '-sUSE_ES6_IMPORT_META=0'])
-    self.assertContained('EXPORT_ES6 and ENVIRONMENT=*node* requires USE_ES6_IMPORT_META to be set', err)
-
   def test_export_es6_allows_export_in_post_js(self):
     self.run_process([EMCC, test_file('hello_world.c'), '-O3', '-sEXPORT_ES6', '--post-js', test_file('export_module.js')])
     src = read_file('a.out.js')

tools/link.py

@@ -1440,11 +1440,6 @@ def phase_linker_setup(options, state, newargs):  # noqa: C901, PLR0912, PLR0915
       if 'MODULARIZE' in user_settings:
         exit_with_error('EXPORT_ES6 requires MODULARIZE to be set')
       settings.MODULARIZE = 1
-    if settings.ENVIRONMENT_MAY_BE_NODE and not settings.USE_ES6_IMPORT_META:
-      # EXPORT_ES6 + ENVIRONMENT=*node* requires the use of import.meta.url
-      if 'USE_ES6_IMPORT_META' in user_settings:
-        exit_with_error('EXPORT_ES6 and ENVIRONMENT=*node* requires USE_ES6_IMPORT_META to be set')
-      settings.USE_ES6_IMPORT_META = 1
 
   if settings.MODULARIZE and not settings.DECLARE_ASM_MODULE_EXPORTS:
     # When MODULARIZE option is used, currently requires declaring all module exports
@@ -2074,7 +2069,7 @@ def phase_source_transforms(options):
 # both main code and libraries.
 # See also: `preprocess` in parseTools.js.
 def fix_es6_import_statements(js_file):
-  if not settings.EXPORT_ES6 or not settings.USE_ES6_IMPORT_META:
+  if not settings.EXPORT_ES6:
     return
 
   src = read_file(js_file)
@@ -2426,7 +2421,7 @@ def modularize():
     # In EXPORT_ES6 + PTHREADS the 'thread' is actually an ES6 module
     # webworker running in strict mode, so doesn't have access to 'document'.
     # In this case use 'import.meta' instead.
-    if settings.EXPORT_ES6 and settings.USE_ES6_IMPORT_META:
+    if settings.EXPORT_ES6:
       script_url = 'import.meta.url'
     else:
       script_url = "typeof document != 'undefined' ? document.currentScript?.src : undefined"

tools/settings.py

@@ -67,7 +67,6 @@
     'HEADLESS',
     'MODULARIZE',
     'EXPORT_ES6',
-    'USE_ES6_IMPORT_META',
     'EXPORT_NAME',
     'DYNAMIC_EXECUTION',
     'PTHREAD_POOL_SIZE',