Allow mutation of EXPORTED_RUNTIME_METHODS in JS libraries (#26389)

This used to work in the past but regressed at some point.

Fixes: #23057

Author: sbc100

src/preamble.js

@@ -768,7 +768,7 @@ function getWasmImports() {
     updateGOT(origExports);
 #endif
 
-#if EXPORTED_RUNTIME_METHODS.includes('wasmExports')
+#if EXPORTED_RUNTIME_METHODS.has('wasmExports')
     Module['wasmExports'] = wasmExports;
 #endif
 

src/runtime_common.js

@@ -126,7 +126,7 @@ var runtimeExited = false;
     let shouldExport = false;
     if (MODULARIZE && EXPORT_ALL) {
       shouldExport = true;
-    } else if (EXPORTED_RUNTIME_METHODS.includes(x)) {
+    } else if (EXPORTED_RUNTIME_METHODS.has(x)) {
       shouldExport = true;
     }
     return shouldExport;

src/utility.mjs

@@ -331,9 +331,27 @@ export function addToCompileTimeContext(object) {
   Object.assign(compileTimeContext, object);
 }
 
+const setLikeSettings = [
+  'EXPORTED_FUNCTIONS',
+  'WASM_EXPORTS',
+  'SIDE_MODULE_EXPORTS',
+  'INCOMING_MODULE_JS_API',
+  'ALL_INCOMING_MODULE_JS_API',
+  'EXPORTED_RUNTIME_METHODS',
+  'WEAK_IMPORTS'
+];
+
 export function applySettings(obj) {
+  // Certain settings are read in as lists, but we convert them to Set
+  // within the compiler, for efficiency.
+  for (const key of setLikeSettings) {
+    if (typeof obj[key] !== 'undefined') {
+      obj[key] = new Set(obj[key]);
+    }
+  }
+
   // Make settings available both in the current / global context
-  // and also in the macro execution contexted.
+  // and also in the macro execution context.
   Object.assign(globalThis, obj);
   addToCompileTimeContext(obj);
 }

test/jslib/test_export.js

@@ -0,0 +1,8 @@
+EXPORTED_RUNTIME_METHODS.add("myFunc");
+
+addToLibrary({
+  $myFunc__postset: 'console.log("myFunc included")',
+  $myFunc: () => {
+    console.log("myFunc called");
+  },
+})

test/test_jslib.py

@@ -757,3 +757,7 @@ class ParentClass {}
   })
   def test_multiline_string(self, args):
     self.do_run_in_out_file_test('jslib/test_multiline_string.c', cflags=['--js-library', test_file('jslib/test_multiline_string.js')] + args)
+
+  def test_export(self):
+    create_file('post.js', 'Module.myFunc();')
+    self.do_runf('hello_world.c', 'myFunc included\nmyFunc called\n', cflags=['--js-library', test_file('jslib/test_export.js'), '--extern-post-js=post.js'])

tools/compiler.mjs

@@ -60,17 +60,9 @@ process.env['EMCC_BUILD_DIR'] = process.cwd();
 
 // In case compiler.mjs is run directly (as in gen_sig_info)
 // ALL_INCOMING_MODULE_JS_API might not be populated yet.
-if (!ALL_INCOMING_MODULE_JS_API.length) {
+if (!ALL_INCOMING_MODULE_JS_API.size) {
   ALL_INCOMING_MODULE_JS_API = INCOMING_MODULE_JS_API;
 }
-
-EXPORTED_FUNCTIONS = new Set(EXPORTED_FUNCTIONS);
-WASM_EXPORTS = new Set(WASM_EXPORTS);
-SIDE_MODULE_EXPORTS = new Set(SIDE_MODULE_EXPORTS);
-INCOMING_MODULE_JS_API = new Set(INCOMING_MODULE_JS_API);
-ALL_INCOMING_MODULE_JS_API = new Set(ALL_INCOMING_MODULE_JS_API);
-EXPORTED_RUNTIME_METHODS = new Set(EXPORTED_RUNTIME_METHODS);
-WEAK_IMPORTS = new Set(WEAK_IMPORTS);
 if (symbolsOnly) {
   INCLUDE_FULL_LIBRARY = 1;
 }