FEATURE: Catch decorateCooked errors from themes/plugins (#15450)

If a theme/plugin raises an error while decorating post content, the decorator will be skipped, and the error reported on the console. Additionally, administrators will be shown a red warning at the top of the screen.

This commit refactors and re-uses some of the logic from the theme-initializer-error-reporting logic. In future, new error reports can be added by doing something like:

```
document.dispatchEvent(
  new CustomEvent("discourse-error", {
    detail: { messageKey: "some.translation.key", error },
  })
);
```

app/assets/javascripts/discourse/app/app.js

@@ -3,7 +3,7 @@ import { buildResolver } from "discourse-common/resolver";
 import { isTesting } from "discourse-common/config/environment";
 
 const _pluginCallbacks = [];
-let _themeErrors = [];
+let _unhandledThemeErrors = [];
 
 const Discourse = Application.extend({
   rootElement: "#main",
@@ -24,12 +24,11 @@ const Discourse = Application.extend({
       if (!module) {
         throw new Error(moduleName + " must export an initializer.");
       }
-    } catch (err) {
+    } catch (error) {
       if (!themeId || isTesting()) {
-        throw err;
+        throw error;
       }
-      _themeErrors.push([themeId, err]);
+      fireThemeErrorEvent({ themeId, error });
-      fireThemeErrorEvent();
       return;
     }
 
@@ -38,12 +37,11 @@ const Discourse = Application.extend({
     init.initialize = (app) => {
       try {
         return oldInitialize.call(init, app.__container__, app);
-      } catch (err) {
+      } catch (error) {
         if (!themeId || isTesting()) {
-          throw err;
+          throw error;
         }
-        _themeErrors.push([themeId, err]);
+        fireThemeErrorEvent({ themeId, error });
-        fireThemeErrorEvent();
       }
     };
 
@@ -92,14 +90,22 @@ function moduleThemeId(moduleName) {
   }
 }
 
-function fireThemeErrorEvent() {
+function fireThemeErrorEvent({ themeId, error }) {
-  const event = new CustomEvent("discourse-theme-error");
+  const event = new CustomEvent("discourse-error", {
-  document.dispatchEvent(event);
+    cancelable: true,
+    detail: { themeId, error },
+  });
+
+  const unhandled = document.dispatchEvent(event);
+
+  if (unhandled) {
+    _unhandledThemeErrors.push(event);
+  }
 }
 
-export function getAndClearThemeErrors() {
+export function getAndClearUnhandledThemeErrors() {
-  const copy = _themeErrors;
+  const copy = _unhandledThemeErrors;
-  _themeErrors = [];
+  _unhandledThemeErrors = [];
   return copy;
 }
 

app/assets/javascripts/discourse/app/lib/plugin-api.js

@@ -118,6 +118,21 @@ function canModify(klass, type, resolverName, changes) {
   }
 }
 
+function wrapWithErrorHandler(func, messageKey) {
+  return function () {
+    try {
+      return func.call(this, ...arguments);
+    } catch (error) {
+      document.dispatchEvent(
+        new CustomEvent("discourse-error", {
+          detail: { messageKey, error },
+        })
+      );
+      return;
+    }
+  };
+}
+
 class PluginApi {
   constructor(version, container) {
     this.version = version;
@@ -309,6 +324,8 @@ class PluginApi {
   decorateCookedElement(callback, opts) {
     opts = opts || {};
 
+    callback = wrapWithErrorHandler(callback, "broken_decorator_alert");
+
     addDecorator(callback, { afterAdopt: !!opts.afterAdopt });
 
     if (!opts.onlyStream) {

app/assets/javascripts/discourse/app/pre-initializers/theme-errors-handler.js

@@ -1,22 +1,43 @@
 import { isTesting } from "discourse-common/config/environment";
-import { getAndClearThemeErrors } from "discourse/app";
+import { getAndClearUnhandledThemeErrors } from "discourse/app";
 import PreloadStore from "discourse/lib/preload-store";
 import getURL from "discourse-common/lib/get-url";
 import I18n from "I18n";
+import { bind } from "discourse-common/utils/decorators";
+
+const showingErrors = new Set();
 
 export default {
   name: "theme-errors-handler",
   after: "inject-discourse-objects",
 
   initialize(container) {
-    const currentUser = container.lookup("current-user:main");
     if (isTesting()) {
       return;
     }
-    renderErrorNotices(currentUser);
+
-    document.addEventListener("discourse-theme-error", () =>
+    this.currentUser = container.lookup("current-user:main");
-      renderErrorNotices(currentUser)
+
-    );
+    getAndClearUnhandledThemeErrors().forEach((e) => {
+      reportThemeError(this.currentUser, e);
+    });
+
+    document.addEventListener("discourse-error", this.handleDiscourseError);
+  },
+
+  cleanup() {
+    document.removeEventListener(this.handleDiscourseError);
+    delete this.currentUser;
+  },
+
+  @bind
+  handleDiscourseError(e) {
+    if (e.detail?.themeId) {
+      reportThemeError(this.currentUser, e);
+    } else {
+      reportGenericError(this.currentUser, e);
+    }
+    e.preventDefault(); // Mark as handled
   },
 };
 
@@ -32,24 +53,42 @@ function reportToLogster(name, error) {
   });
 }
 
-function renderErrorNotices(currentUser) {
+function reportThemeError(currentUser, e) {
-  getAndClearThemeErrors().forEach(([themeId, error]) => {
+  const { themeId, error } = e.detail;
+
   const name =
     PreloadStore.get("activatedThemes")[themeId] || `(theme-id: ${themeId})`;
   /* eslint-disable-next-line no-console */
   console.error(`An error occurred in the "${name}" theme/component:`, error);
   reportToLogster(name, error);
-    if (!currentUser || !currentUser.admin) {
+
-      return;
-    }
   const path = getURL("/admin/customize/themes");
   const message = I18n.t("themes.broken_theme_alert", {
     theme: name,
     path: `<a href="${path}">${path}</a>`,
   });
+  displayErrorNotice(currentUser, message);
+}
+
+function reportGenericError(currentUser, e) {
+  const { messageKey, error } = e.detail;
+
+  /* eslint-disable-next-line no-console */
+  console.error(error);
+
+  if (messageKey && !showingErrors.has(messageKey)) {
+    showingErrors.add(messageKey);
+    displayErrorNotice(currentUser, I18n.t(messageKey));
+  }
+}
+
+function displayErrorNotice(currentUser, message) {
+  if (!currentUser?.admin) {
+    return;
+  }
+
   const alertDiv = document.createElement("div");
   alertDiv.classList.add("broken-theme-alert");
   alertDiv.innerHTML = `⚠️ ${message}`;
   document.body.prepend(alertDiv);
-  });
 }

config/locales/client.en.yml

@@ -195,6 +195,8 @@ en:
       default_description: "Default"
       broken_theme_alert: "Your site may not work because theme / component %{theme} has errors. Disable it at %{path}."
 
+    broken_decorator_alert: "Posts may not display correctly because one of the post content decorators on your site raised an error. Check the browser developer tools for more information."
+
     s3:
       regions:
         ap_northeast_1: "Asia Pacific (Tokyo)"