Fix autolinking errors due to regex and email validation

Fix some edge cases in the autolinking logic with the regex as well as
validating email domains and add unit tests for them.

Fixes: #19462

test/unit/autolinker_spec.js

@@ -87,6 +87,9 @@ describe("autolinker", function () {
         "[email protected]", // Keep the original case.
         "mailto:[email protected]",
       ],
+      ["[email protected]", "mailto:[email protected]"],
+      ["[email protected]", "mailto:[email protected]"],
+      ["<[email protected]>", "mailto:[email protected]"],
     ]);
   });
 
@@ -140,6 +143,7 @@ describe("autolinker", function () {
         "http//[00:00:00:00:00:00", // Invalid IPv6 address.
         "http//[]", // Empty IPv6 address.
         "abc.example.com", // URL without scheme.
+        "JD?M$0QP)lKn06l1apKDC@\\qJ4B!!(5m+j.7F790m", // Not a valid email.
       ].join("\n")
     );
     expect(matches.length).toEqual(0);

web/autolinker.js

@@ -96,31 +96,37 @@ class Autolinker {
   static #regex;
 
   static findLinks(text) {
-    // Regex can be tested and verified at https://regex101.com/r/zgDwPE/1.
+    // Regex can be tested and verified at https://regex101.com/r/rXoLiT/2.
     this.#regex ??=
-      /\b(?:https?:\/\/|mailto:|www\.)(?:[[\S--\[]--\p{P}]|\/|[\p{P}--\[]+[[\S--\[]--\p{P}])+|\b[[\S--@]--\{]+@[\S--.]+\.[[\S--\[]--\p{P}]{2,}/gmv;
+      /\b(?:https?:\/\/|mailto:|www\.)(?:[\S--[\p{P}<>]]|\/|[\S--[\[\]]]+[\S--[\p{P}<>]])+|\b[\S--[@\p{Ps}\p{Pe}<>]]+@([\S--[\p{P}<>]]+(?:\.[\S--[\p{P}<>]]+)+)/gmv;
 
     const [normalizedText, diffs] = normalize(text);
     const matches = normalizedText.matchAll(this.#regex);
     const links = [];
     for (const match of matches) {
-      const raw =
-        match[0].startsWith("www.") ||
-        match[0].startsWith("mailto:") ||
-        match[0].startsWith("http://") ||
-        match[0].startsWith("https://")
-          ? match[0]
-          : `mailto:${match[0]}`;
-      const url = createValidAbsoluteUrl(raw, null, {
+      const [url, emailDomain] = match;
+      let raw;
+      if (
+        url.startsWith("www.") ||
+        url.startsWith("http://") ||
+        url.startsWith("https://")
+      ) {
+        raw = url;
+      } else if (URL.canParse(`http://${emailDomain}`)) {
+        raw = url.startsWith("mailto:") ? url : `mailto:${url}`;
+      } else {
+        continue;
+      }
+      const absoluteURL = createValidAbsoluteUrl(raw, null, {
         addDefaultProtocol: true,
       });
-      if (url) {
+      if (absoluteURL) {
         const [index, length] = getOriginalIndex(
           diffs,
           match.index,
-          match[0].length
+          url.length
         );
-        links.push({ url: url.href, index, length });
+        links.push({ url: absoluteURL.href, index, length });
       }
     }
     return links;