1 files changed, 113 insertions, 0 deletions
diff --git a/dom/base/test/unit/test_blockParsing.js b/dom/base/test/unit/test_blockParsing.js
new file mode 100644
index 0000000000..cdc4f852e1
--- /dev/null
+++ b/dom/base/test/unit/test_blockParsing.js
@@ -0,0 +1,113 @@
+"use strict";
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+const { XPCShellContentUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/XPCShellContentUtils.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+XPCShellContentUtils.init(this);
+
+function delay() {
+  return new Promise(resolve => {
+    setTimeout(resolve, 0);
+  });
+}
+
+const server = XPCShellContentUtils.createHttpServer({
+  hosts: ["example.com"],
+});
+
+// XML document with only a <script> tag as the document element.
+const PAGE_URL = "http://example.com/";
+server.registerPathHandler("/", (request, response) => {
+  response.setHeader("Content-Type", "application/xhtml+xml");
+  response.write(String.raw`<!DOCTYPE html>
+    <script xmlns="http://www.w3.org/1999/xhtml" src="slow.js"/>
+  `);
+});
+
+let resolveResumeScriptPromise;
+let resumeScriptPromise = new Promise(resolve => {
+  resolveResumeScriptPromise = resolve;
+});
+
+let resolveScriptRequestPromise;
+let scriptRequestPromise = new Promise(resolve => {
+  resolveScriptRequestPromise = resolve;
+});
+
+// An empty script which waits to complete until `resumeScriptPromise`
+// resolves.
+server.registerPathHandler("/slow.js", async (request, response) => {
+  response.processAsync();
+  resolveScriptRequestPromise();
+
+  await resumeScriptPromise;
+
+  response.setHeader("Content-type", "text/javascript");
+  response.write("");
+  response.finish();
+});
+
+// Tests that attempting to block parsing for a <script> tag while the
+// parser is already blocked is handled correctly, and does not cause
+// crashes or hangs.
+add_task(async function test_nested_blockParser() {
+  // Wait for the document element of the page to be inserted, and block
+  // the parser when it is.
+  let resolveBlockerPromise;
+  let blockerPromise;
+  let docElementPromise = TestUtils.topicObserved(
+    "document-element-inserted",
+    doc => {
+      if (doc.location.href === PAGE_URL) {
+        blockerPromise = new Promise(resolve => {
+          resolveBlockerPromise = resolve;
+        });
+
+        doc.blockParsing(blockerPromise);
+        return true;
+      }
+      return false;
+    }
+  );
+
+  // Begin loading the page.
+  let pagePromise = XPCShellContentUtils.loadContentPage(PAGE_URL, {
+    remote: false,
+  });
+
+  // Wait for the document element to be inserted.
+  await docElementPromise;
+  // Wait for the /slow.js script request to initiate.
+  await scriptRequestPromise;
+
+  // Make some trips through the event loop to be safe.
+  await delay();
+  await delay();
+
+  // Allow the /slow.js script request to complete.
+  resolveResumeScriptPromise();
+
+  // Make some trips through the event loop so that the <script> request
+  // unblocks the parser.
+  await delay();
+  await delay();
+
+  // Release the parser blocker added in the observer above.
+  resolveBlockerPromise();
+
+  // Make some trips through the event loop to allow the parser to
+  // unblock.
+  await delay();
+  await delay();
+
+  // Wait for the document to finish loading, and then close it.
+  let page = await pagePromise;
+  await page.close();
+});