[file_packager] Use await when waiting for fetch to complete. (#24992)

Author: sbc100

test/code_size/test_codesize_file_preload.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 22730,
-  "a.out.js.gz": 9405,
+  "a.out.js": 22699,
+  "a.out.js.gz": 9379,
   "a.out.nodebug.wasm": 1733,
   "a.out.nodebug.wasm.gz": 980,
-  "total": 24463,
-  "total_gz": 10385,
+  "total": 24432,
+  "total_gz": 10359,
   "sent": [
     "a (fd_write)"
   ],

test/other/codesize/test_codesize_file_preload.expected.js

@@ -100,19 +100,12 @@ Module["expectedDataFileDownloads"]++;
       }
       return packageData.buffer;
     }
-    var fetchedCallback;
+    var fetchPromise;
     var fetched = Module["getPreloadedPackage"]?.(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE);
     if (!fetched) {
       // Note that we don't use await here because we want to execute the
       // the rest of this function immediately.
-      fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE).then(data => {
-        if (fetchedCallback) {
-          fetchedCallback(data);
-          fetchedCallback = null;
-        } else {
-          fetched = data;
-        }
-      });
+      fetchPromise = fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE);
     }
     async function runWithFS(Module) {
       function assert(check, msg) {
@@ -141,12 +134,10 @@ Module["expectedDataFileDownloads"]++;
       Module["preloadResults"][PACKAGE_NAME] = {
         fromCache: false
       };
-      if (fetched) {
-        processPackageData(fetched);
-        fetched = null;
-      } else {
-        fetchedCallback = processPackageData;
+      if (!fetched) {
+        fetched = await fetchPromise;
       }
+      processPackageData(fetched);
     }
     if (Module["calledRun"]) {
       runWithFS(Module);

tools/file_packager.py

@@ -1044,31 +1044,21 @@ def generate_js(data_target, data_files, metadata):
       # Only tricky bit is the fetch is async, but also when runWithFS is called
       # is async, so we handle both orderings.
       ret += '''
-      var fetchedCallback;
+      var fetchPromise;
       var fetched = Module['getPreloadedPackage']?.(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE);
 
       if (!fetched) {
         // Note that we don't use await here because we want to execute the
         // the rest of this function immediately.
-        fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE)
-          .then((data) => {
-            if (fetchedCallback) {
-              fetchedCallback(data);
-              fetchedCallback = null;
-            } else {
-              fetched = data;
-            }
-          })%s;
+        fetchPromise = fetchRemotePackage(REMOTE_PACKAGE_NAME, REMOTE_PACKAGE_SIZE)%s;
       }\n''' % catch_handler
 
       code += '''
       Module['preloadResults'][PACKAGE_NAME] = {fromCache: false};
-      if (fetched) {
-        processPackageData(fetched);
-        fetched = null;
-      } else {
-        fetchedCallback = processPackageData;
-      }\n'''
+      if (!fetched) {
+        fetched = await fetchPromise;
+      }
+      processPackageData(fetched);\n'''
 
   ret += '''
     async function runWithFS(Module) {\n'''