FIX: Do not autocomplete categories or emojis in code blocks (#8433)

Emojis and category autocomplete show up often when writing code
snippets, which makes it easy to insert unwanted text by mistake.

test/javascripts/lib/utilities-test.js.es6

@@ -9,7 +9,9 @@ import {
   setDefaultHomepage,
   caretRowCol,
   setCaretPosition,
-  fillMissingDates
+  fillMissingDates,
+  getCodeBlocks,
+  inCodeBlock
 } from "discourse/lib/utilities";
 
 QUnit.module("lib:utilities");
@@ -186,3 +188,50 @@ QUnit.test("fillMissingDates", assert => {
     "it returns a JSON array with 31 dates"
   );
 });
+
+QUnit.test("getCodeBlocks - works with [code]", assert => {
+  assert.deepEqual(
+    getCodeBlocks("[code]\nfoo\n[/code]\n\nbar\n\n[code]\nbaz"),
+    [
+      [0, 18],
+      [25, 35]
+    ]
+  );
+});
+
+QUnit.test("getCodeBlocks - works with backticks", assert => {
+  assert.deepEqual(getCodeBlocks("foo `bar\nbar`! `baz"), [
+    [4, 13],
+    [15, 19]
+  ]);
+});
+
+QUnit.test("getCodeBlocks - works with triple backticks", assert => {
+  assert.deepEqual(getCodeBlocks("```\nfoo\n```\n\nbar\n\n```\nbaz"), [
+    [0, 11],
+    [18, 25]
+  ]);
+});
+
+QUnit.test("inCodeBlock", assert => {
+  const raw =
+    "bar\n\n```\nfoo\n```\n\nbar\n\n`foo\nfoo`\n\nbar\n\n[code]\nfoo\n[/code]\n\nbar`foo";
+
+  assert.notOk(inCodeBlock(raw, 4));
+  assert.ok(inCodeBlock(raw, 5));
+  assert.ok(inCodeBlock(raw, 16));
+  assert.notOk(inCodeBlock(raw, 17));
+
+  assert.notOk(inCodeBlock(raw, 22));
+  assert.ok(inCodeBlock(raw, 23));
+  assert.ok(inCodeBlock(raw, 32));
+  assert.notOk(inCodeBlock(raw, 33));
+
+  assert.notOk(inCodeBlock(raw, 38));
+  assert.ok(inCodeBlock(raw, 39));
+  assert.ok(inCodeBlock(raw, 57));
+  assert.notOk(inCodeBlock(raw, 58));
+
+  assert.notOk(inCodeBlock(raw, 61));
+  assert.ok(inCodeBlock(raw, 62));
+});