1 files changed, 60 insertions, 0 deletions
diff --git a/browser/base/content/test/tabPrompts/browser_abort_when_in_modal_state.js b/browser/base/content/test/tabPrompts/browser_abort_when_in_modal_state.js
new file mode 100644
index 0000000000..cb3a1f72d6
--- /dev/null
+++ b/browser/base/content/test/tabPrompts/browser_abort_when_in_modal_state.js
@@ -0,0 +1,60 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+
+/**
+ * Check that if we're using a window-modal prompt,
+ * the next synchronous window-internal modal prompt aborts rather than
+ * leaving us in a deadlock about how to enter modal state.
+ */
+add_task(async function test_check_multiple_prompts() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["prompts.windowPromptSubDialog", true]],
+  });
+  let container = document.getElementById("window-modal-dialog");
+  let dialogPromise = BrowserTestUtils.promiseAlertDialogOpen();
+
+  let firstDialogClosedPromise = new Promise(resolve => {
+    // Avoid blocking the test on the (sync) alert by sticking it in a timeout:
+    setTimeout(() => {
+      Services.prompt.alertBC(
+        window.browsingContext,
+        Ci.nsIPrompt.MODAL_TYPE_WINDOW,
+        "Some title",
+        "some message"
+      );
+      resolve();
+    }, 0);
+  });
+  let dialogWin = await dialogPromise;
+
+  // Check circumstances of opening.
+  ok(
+    !dialogWin.docShell.chromeEventHandler,
+    "Should not have embedded the dialog."
+  );
+
+  PromiseTestUtils.expectUncaughtRejection(/could not be shown/);
+  let rv = Services.prompt.confirm(
+    window,
+    "I should not appear",
+    "because another prompt was open"
+  );
+  is(rv, false, "Prompt should have been canceled.");
+
+  info("Accepting dialog");
+  dialogWin.document.querySelector("dialog").acceptDialog();
+
+  await firstDialogClosedPromise;
+
+  await BrowserTestUtils.waitForMutationCondition(
+    container,
+    { childList: true, attributes: true },
+    () => !container.hasChildNodes() && !container.open
+  );
+});