Use fetch rather than XMLHttpRequest for downloading Wasm files (#22015)

This PR switches requests for Wasm files to be loaded with `fetch()` rather than `XMLHttpRequest()`.

This fixes running in service workers where `XMLHttpRequest` is not available.

Partially fixes #22003, only applies to Wasm files.

Author: seanmorris

AUTHORS

@@ -600,3 +600,4 @@ a license to everyone to use it as detailed in LICENSE.)
 * YAMAMOTO Takashi <[email protected]>
 * Artur Gatin <[email protected]> (copyright owned by Teladoc Health, Inc.)
 * Christian Lloyd <[email protected]> (copyright owned by Teladoc Health, Inc.)
+* Sean Morris <[email protected]>

src/polyfill/fetch.js

@@ -0,0 +1,80 @@
+// Fetch polyfill from https://github.com/developit/unfetch
+// License:
+//==============================================================================
+// Copyright (c) 2017 Jason Miller
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//==============================================================================
+
+#if !POLYFILL
+#error "this file should never be included unless POLYFILL is set"
+#endif
+
+if (typeof globalThis.fetch == 'undefined') {
+  globalThis.fetch = function (url, options) {
+    options = options || {};
+    return new Promise((resolve, reject) => {
+      const request = new XMLHttpRequest();
+      const keys = [];
+      const headers = {};
+
+      request.responseType = 'arraybuffer';
+
+      const response = () => ({
+        ok: ((request.status / 100) | 0) == 2, // 200-299
+        statusText: request.statusText,
+        status: request.status,
+        url: request.responseURL,
+        text: () => Promise.resolve(request.responseText),
+        json: () => Promise.resolve(request.responseText).then(JSON.parse),
+        blob: () => Promise.resolve(new Blob([request.response])),
+        arrayBuffer: () => Promise.resolve(request.response),
+        clone: response,
+        headers: {
+          keys: () => keys,
+          entries: () => keys.map((n) => [n, request.getResponseHeader(n)]),
+          get: (n) => request.getResponseHeader(n),
+          has: (n) => request.getResponseHeader(n) != null,
+        },
+      });
+
+      request.open(options.method || "get", url, true);
+
+      request.onload = () => {
+        request
+          .getAllResponseHeaders()
+          .toLowerCase()
+          .replace(/^(.+?):/gm, (m, key) => {
+            headers[key] || keys.push((headers[key] = key));
+          });
+        resolve(response());
+      };
+
+      request.onerror = reject;
+
+      request.withCredentials = options.credentials == "include";
+
+      for (const i in options.headers) {
+        request.setRequestHeader(i, options.headers[i]);
+      }
+
+      request.send(options.body || null);
+    });
+  }
+}

src/shell.js

@@ -61,6 +61,11 @@ var Module = typeof {{{ EXPORT_NAME }}} != 'undefined' ? {{{ EXPORT_NAME }}} : {
 // See https://caniuse.com/mdn-javascript_builtins_bigint64array
 #include "polyfill/bigint64array.js"
 #endif
+
+#if MIN_CHROME_VERSION < 40 || MIN_FIREFOX_VERSION < 39 || MIN_SAFARI_VERSION < 103000
+// See https://caniuse.com/fetch
+#include "polyfill/fetch.js"
+#endif
 #endif // POLYFILL
 
 #if MODULARIZE

src/web_or_worker_shell_read.js

@@ -22,17 +22,12 @@
   }
 
   readAsync = (url, onload, onerror) => {
-    var xhr = new XMLHttpRequest();
-    xhr.open('GET', url, true);
-    xhr.responseType = 'arraybuffer';
-    xhr.onload = () => {
-      if (xhr.status == 200 || (xhr.status == 0 && xhr.response)) { // file URLs can return 0
-        onload(xhr.response);
-        return;
+    fetch(url)
+    .then((response) => {
+      if (response.ok) {
+        return response.arrayBuffer();
       }
-      onerror();
-    };
-    xhr.onerror = onerror;
-    xhr.send(null);
-  }
-
+      return Promise.reject(new Error(response.statusText + ' : ' + response.url));
+    })
+    .then(onload, onerror)
+  };

test/common.py

@@ -2272,7 +2272,7 @@ def compile_btest(self, filename, args, reporting=Reporting.FULL):
         # also include report_result.c and force-include report_result.h
         self.run_process([EMCC, '-c', '-I' + TEST_ROOT,
                           '-DEMTEST_PORT_NUMBER=%d' % self.port,
-                          test_file('report_result.c')] + self.get_emcc_args(compile_only=True))
+                          test_file('report_result.c')] + self.get_emcc_args(compile_only=True) + (['-fPIC'] if '-fPIC' in args else []))
         args += ['report_result.o', '-include', test_file('report_result.h')]
     if EMTEST_BROWSER == 'node':
       args.append('-DEMTEST_NODE')

test/test_browser.py

@@ -700,7 +700,9 @@ def setup(assetLocalization):
           <center><canvas id='canvas' width='256' height='256'></canvas></center>
           <hr><div id='output'></div><hr>
           <script type='text/javascript'>
-            window.onerror = (error) => {
+            const handler = (event) => {
+              event.stopImmediatePropagation();
+              const error = String(event instanceof ErrorEvent ? event.message : (event.reason || event));
               window.disableErrorReporting = true;
               window.onerror = null;
               var result = error.includes("test.data") ? 1 : 0;
@@ -709,6 +711,8 @@ def setup(assetLocalization):
               xhr.send();
               setTimeout(function() { window.close() }, 1000);
             }
+            window.addEventListener('error', handler);
+            window.addEventListener('unhandledrejection', handler);
             var Module = {
               locateFile: function (path, prefix) {if (path.endsWith(".wasm")) {return prefix + path;} else {return "''' + assetLocalization + r'''" + path;}},
               print: (function() {
@@ -5545,6 +5549,39 @@ def test_webpack(self):
     shutil.copyfile('webpack/src/hello.wasm', 'webpack/dist/hello.wasm')
     self.run_browser('webpack/dist/index.html', '/report_result?exit:0')
 
+  def test_fetch_polyfill_shared_lib(self):
+    create_file('library.c', r'''
+      #include <stdio.h>
+      int library_func() {
+        return 42;
+      }
+    ''')
+    create_file('main.c', r'''
+      #include <dlfcn.h>
+      #include <stdio.h>
+      int main() {
+        void *lib_handle = dlopen("/library.so", RTLD_NOW);
+        typedef int (*voidfunc)();
+        voidfunc x = (voidfunc)dlsym(lib_handle, "library_func");
+        return x();
+      }
+    ''')
+
+    self.run_process([EMCC, 'library.c', '-sSIDE_MODULE', '-O2', '-o', 'library.so'])
+
+    def test(args, expect_fail):
+      self.compile_btest('main.c', ['-fPIC', 'library.so', '-sMAIN_MODULE=2', '-sEXIT_RUNTIME', '-o', 'a.out.html'] + args)
+      if expect_fail:
+        js = read_file('a.out.js')
+        create_file('a.out.js', 'fetch = undefined;\n' + js)
+        return self.run_browser('a.out.html', '/report_result?abort:TypeError')
+      else:
+        return self.run_browser('a.out.html', '/report_result?exit:42')
+
+    test([], expect_fail=True)
+    test(['-sLEGACY_VM_SUPPORT'], expect_fail=False)
+    test(['-sLEGACY_VM_SUPPORT', '-sNO_POLYFILL'], expect_fail=True)
+
 
 class emrun(RunnerCore):
   def test_emrun_info(self):