1 files changed, 187 insertions, 0 deletions
diff --git a/browser/extensions/webcompat/shims/google-analytics-and-tag-manager.js b/browser/extensions/webcompat/shims/google-analytics-and-tag-manager.js
new file mode 100644
index 0000000000..8809fca8ec
--- /dev/null
+++ b/browser/extensions/webcompat/shims/google-analytics-and-tag-manager.js
@@ -0,0 +1,187 @@
+/* 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/. */
+
+"use strict";
+
+/**
+ * Bug 1713687 - Shim Google Analytics and Tag Manager
+ *
+ * Sites often rely on the Google Analytics window object and will
+ * break if it fails to load or is blocked. This shim works around
+ * such breakage.
+ *
+ * Sites also often use the Google Optimizer (asynchide) code snippet,
+ * only for it to cause multi-second delays if Google Analytics does
+ * not load. This shim also avoids such delays.
+ *
+ * They also rely on Google Tag Manager, which often goes hand-in-
+ * hand with Analytics, but is not always blocked by anti-tracking
+ * lists. Handling both in the same shim handles both cases.
+ */
+
+if (window[window.GoogleAnalyticsObject || "ga"]?.loaded === undefined) {
+  const DEFAULT_TRACKER_NAME = "t0";
+
+  const trackers = new Map();
+
+  const run = function (fn, ...args) {
+    if (typeof fn === "function") {
+      try {
+        fn(...args);
+      } catch (e) {
+        console.error(e);
+      }
+    }
+  };
+
+  const create = (id, cookie, name, opts) => {
+    id = id || opts?.trackerId;
+    if (!id) {
+      return undefined;
+    }
+    cookie = cookie || opts?.cookieDomain || "_ga";
+    name = name || opts?.name || DEFAULT_TRACKER_NAME;
+    if (!trackers.has(name)) {
+      let props;
+      try {
+        props = new Map(Object.entries(opts));
+      } catch (_) {
+        props = new Map();
+      }
+      trackers.set(name, {
+        get(p) {
+          if (p === "name") {
+            return name;
+          } else if (p === "trackingId") {
+            return id;
+          } else if (p === "cookieDomain") {
+            return cookie;
+          }
+          return props.get(p);
+        },
+        ma() {},
+        requireSync() {},
+        send() {},
+        set(p, v) {
+          if (typeof p !== "object") {
+            p = Object.fromEntries([[p, v]]);
+          }
+          for (const k in p) {
+            props.set(k, p[k]);
+            if (k === "hitCallback") {
+              run(p[k]);
+            }
+          }
+        },
+      });
+    }
+    return trackers.get(name);
+  };
+
+  const cmdRE = /((?<name>.*?)\.)?((?<plugin>.*?):)?(?<method>.*)/;
+
+  function ga(cmd, ...args) {
+    if (arguments.length === 1 && typeof cmd === "function") {
+      run(cmd, trackers.get(DEFAULT_TRACKER_NAME));
+      return undefined;
+    }
+
+    if (typeof cmd !== "string") {
+      return undefined;
+    }
+
+    const groups = cmdRE.exec(cmd)?.groups;
+    if (!groups) {
+      console.error("Could not parse GA command", cmd);
+      return undefined;
+    }
+
+    let { name, plugin, method } = groups;
+
+    if (plugin) {
+      return undefined;
+    }
+
+    if (cmd === "set") {
+      trackers.get(name)?.set(args[0], args[1]);
+    }
+
+    if (method === "remove") {
+      trackers.delete(name);
+      return undefined;
+    }
+
+    if (cmd === "send") {
+      run(args.at(-1)?.hitCallback);
+      return undefined;
+    }
+
+    if (method === "create") {
+      let id, cookie, fields;
+      for (const param of args.slice(0, 4)) {
+        if (typeof param === "object") {
+          fields = param;
+          break;
+        }
+        if (id === undefined) {
+          id = param;
+        } else if (cookie === undefined) {
+          cookie = param;
+        } else {
+          name = param;
+        }
+      }
+      return create(id, cookie, name, fields);
+    }
+
+    return undefined;
+  }
+
+  Object.assign(ga, {
+    create: (a, b, c, d) => ga("create", a, b, c, d),
+    getAll: () => Array.from(trackers.values()),
+    getByName: name => trackers.get(name),
+    loaded: true,
+    remove: t => ga("remove", t),
+  });
+
+  // Process any GA command queue the site pre-declares (bug 1736850)
+  const q = window[window.GoogleAnalyticsObject || "ga"]?.q;
+  window[window.GoogleAnalyticsObject || "ga"] = ga;
+
+  if (Array.isArray(q)) {
+    const push = o => {
+      ga(...o);
+      return true;
+    };
+    q.push = push;
+    q.forEach(o => push(o));
+  }
+
+  // Also process the Google Tag Manager dataLayer (bug 1713688)
+  const dl = window.dataLayer;
+
+  if (Array.isArray(dl) && !dl.find(e => e["gtm.start"])) {
+    const push = function (o) {
+      setTimeout(() => run(o?.eventCallback), 1);
+      return true;
+    };
+    dl.push = push;
+    dl.forEach(o => push(o));
+  }
+
+  // Run dataLayer.hide.end to handle asynchide (bug 1628151)
+  run(window.dataLayer?.hide?.end);
+}
+
+if (!window?.gaplugins?.Linker) {
+  window.gaplugins = window.gaplugins || {};
+  window.gaplugins.Linker = class {
+    autoLink() {}
+    decorate(url) {
+      return url;
+    }
+    passthrough() {}
+  };
+}