PLT-7474 Stopped requiring confirmation for mentions in code blocks (#7375)

* PLT-7474 Stopped requiring confirmation for mentions in code blocks

* Stopped mentioning people from code blocks using ~~~

webapp/utils/post_utils.jsx

@@ -113,5 +113,15 @@ export function containsAtMention(text, key) {
     }
 
     // This doesn't work for at mentions containing periods or hyphens
-    return new RegExp(`\\B${key}\\b`, 'i').test(text);
+    return new RegExp(`\\B${key}\\b`, 'i').test(removeCode(text));
+}
+
+// Returns a given text string with all Markdown code replaced with whitespace.
+export function removeCode(text) {
+    // These patterns should match the ones in app/notification.go, except JavaScript doesn't
+    // support \z for the end of the text in multiline mode, so we use $(?![\r\n])
+    const codeBlockPattern = /^[^\S\n]*[`~]{3}.*$[\s\S]+?(^[^\S\n]*[`~]{3}$|$(?![\r\n]))/m;
+    const inlineCodePattern = /`+(?:.+?|.*?\n(.*?\S.*?\n)*.*?)`+/m;
+
+    return text.replace(codeBlockPattern, '').replace(inlineCodePattern, ' ');
 }