1 files changed, 41 insertions, 0 deletions
diff --git a/devtools/client/webconsole/test/browser/browser_jsterm_insert_tab_when_overflows_no_scroll.js b/devtools/client/webconsole/test/browser/browser_jsterm_insert_tab_when_overflows_no_scroll.js
new file mode 100644
index 0000000000..6a5ab75a50
--- /dev/null
+++ b/devtools/client/webconsole/test/browser/browser_jsterm_insert_tab_when_overflows_no_scroll.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Check that when the input overflows, inserting a tab doesn't not impact the
+// scroll position. See Bug 1578283.
+
+"use strict";
+
+const TEST_URI = "data:text/html,<!DOCTYPE html><meta charset=utf8>";
+
+add_task(async function () {
+  const hud = await openNewTabAndConsole(TEST_URI);
+  const cmScroller = hud.ui.outputNode.querySelector(".CodeMirror-scroll");
+
+  info("Fill in the input with a hundred lines to make it overflow");
+  await setInputValue(hud, "x;\n".repeat(100));
+
+  ok(hasVerticalOverflow(cmScroller), "input overflows");
+
+  info("Put the cursor at the very beginning");
+  hud.jsterm.editor.setCursor({
+    line: 0,
+    ch: 0,
+  });
+  is(cmScroller.scrollTop, 0, "input is scrolled all the way up");
+
+  info("Move the cursor one line down and hit Tab");
+  EventUtils.synthesizeKey("KEY_ArrowDown");
+  EventUtils.synthesizeKey("KEY_Tab");
+  checkInputValueAndCursorPosition(
+    hud,
+    `x;\n\t|x;\n${"x;\n".repeat(98)}`,
+    "a tab char was added at the start of the second line after hitting Tab"
+  );
+  is(
+    cmScroller.scrollTop,
+    0,
+    "Scroll position wasn't affected by new char addition"
+  );
+});