Add adjustWasmImports incoming Module setting

emcc.py

@@ -73,7 +73,8 @@
 # These symbol names are allowed in INCOMING_MODULE_JS_API but are not part of the
 # default set.
 EXTRA_INCOMING_JS_API = [
-  'fetchSettings'
+  'fetchSettings',
+  'adjustWasmImports',
 ]
 
 SIMD_INTEL_FEATURE_TOWER = ['-msse', '-msse2', '-msse3', '-mssse3', '-msse4.1', '-msse4.2', '-msse4', '-mavx', '-mavx2']

src/preamble.js

@@ -977,6 +977,12 @@ function getWasmImports() {
 
   var info = getWasmImports();
 
+#if expectToReceiveOnModule('adjustWasmImports')
+  if (Module['adjustWasmImports']) {
+    Module['adjustWasmImports'](info);
+  }
+#endif
+
 #if expectToReceiveOnModule('instantiateWasm')
   // User shell pages can write their own Module.instantiateWasm = function(imports, successCallback) callback
   // to manually instantiate the Wasm module themselves. This allows pages to

test/other/test_adjust_wasm_imports.c

@@ -0,0 +1,13 @@
+#include "assert.h"
+#include "stdio.h"
+
+int __attribute__((import_module("env"), import_name("js_fun"))) js_func(int x, int y);
+
+int main() {
+    int x = 7;
+    int y = 9;
+    printf("Calling js_func(%d, %d);\n", x, y);
+    int res = js_func(x, y);
+    assert(res == 16);
+    return 0;
+}

test/test_other.py

@@ -15690,6 +15690,17 @@ def test_instantiate_wasm(self):
       }''')
     self.do_runf('test_manual_wasm_instantiate.c', emcc_args=['--pre-js=pre.js'])
 
+  @also_with_modularize
+  def test_adjust_wasm_imports(self):
+    create_file('pre.js', '''
+      Module['adjustWasmImports'] = (imports) => {
+        imports.env.js_fun = (x, y) => x + y;
+      };
+    ''')
+    self.emcc_args.remove('-Werror')
+    self.set_setting('INCOMING_MODULE_JS_API', 'adjustWasmImports')
+    self.do_runf('other/test_adjust_wasm_imports.c', emcc_args=['--pre-js=pre.js', '-sERROR_ON_UNDEFINED_SYMBOLS=0'])
+
   def test_late_module_api_assignment(self):
     # When sync instantiation is used (or when async/await is used in MODULARIZE mode) certain
     # Module properties cannot be assigned in `--post-js` code because its too late by the time