FEATURE: Show warning banner for critical JS deprecations to admins (#25091)

Ported from d95706b25a

This is enabled by default, but can be disabled via the `warn_critical_js_deprecations` hidden site setting.

The `warn_critical_js_deprecations_message` site setting can be used by hosting providers to add a sentence to the warning message (e.g. a date when they will be deploying the Ember 5 upgrade).

app/assets/javascripts/discourse/app/instance-initializers/boot-services.js

@@ -1,5 +1,6 @@
 export default {
   initialize(owner) {
     owner.lookup("service:client-error-handler");
+    owner.lookup("service:deprecation-warning-handler");
   },
 };

app/assets/javascripts/discourse/app/services/deprecation-warning-handler.js

@@ -0,0 +1,111 @@
+import { registerDeprecationHandler } from "@ember/debug";
+import Service, { inject as service } from "@ember/service";
+import { addGlobalNotice } from "discourse/components/global-notice";
+import identifySource from "discourse/lib/source-identifier";
+import { escapeExpression } from "discourse/lib/utilities";
+import { registerDeprecationHandler as registerDiscourseDeprecationHandler } from "discourse-common/lib/deprecated";
+import { bind } from "discourse-common/utils/decorators";
+import I18n from "discourse-i18n";
+
+// Deprecations matching patterns on this list will trigger warnings for admins.
+// To avoid 'crying wolf', we should only add values here when we're sure they're
+// not being triggered by core or official themes/plugins.
+export const CRITICAL_DEPRECATIONS = [
+  /^discourse.modal-controllers$/,
+  /^(?!discourse\.)/, // All unsilenced ember deprecations
+];
+
+// Deprecation handling APIs don't have any way to unregister handlers, so we set up permenant
+// handlers and link them up to the application lifecycle using module-local state.
+let handler;
+registerDeprecationHandler((message, opts, next) => {
+  handler?.(message, opts);
+  return next(message, opts);
+});
+registerDiscourseDeprecationHandler((message, opts) =>
+  handler?.(message, opts)
+);
+
+export default class DeprecationWarningHandler extends Service {
+  @service currentUser;
+  @service siteSettings;
+
+  #adminWarned = false;
+
+  constructor() {
+    super(...arguments);
+    handler = this.handle;
+  }
+
+  willDestroy() {
+    handler = null;
+  }
+
+  @bind
+  handle(message, opts) {
+    const workflowConfigs = window.deprecationWorkflow?.config?.workflow;
+    const matchingConfig = workflowConfigs.find(
+      (config) => config.matchId === opts.id
+    );
+
+    if (matchingConfig && matchingConfig.handler === "silence") {
+      return;
+    }
+
+    const source = identifySource();
+    if (source?.type === "browser-extension") {
+      return;
+    }
+
+    this.maybeNotifyAdmin(opts.id, source);
+  }
+
+  maybeNotifyAdmin(id, source) {
+    if (this.#adminWarned) {
+      return;
+    }
+
+    if (!this.currentUser?.admin) {
+      return;
+    }
+
+    if (!this.siteSettings.warn_critical_js_deprecations) {
+      return;
+    }
+
+    if (CRITICAL_DEPRECATIONS.some((pattern) => pattern.test(id))) {
+      this.notifyAdmin(id, source);
+    }
+  }
+
+  notifyAdmin(id, source) {
+    this.#adminWarned = true;
+
+    let notice = I18n.t("critical_deprecation.notice");
+
+    if (this.siteSettings.warn_critical_js_deprecations_message) {
+      notice += " " + this.siteSettings.warn_critical_js_deprecations_message;
+    }
+
+    if (source?.type === "theme") {
+      notice +=
+        " " +
+        I18n.t("critical_deprecation.theme_source", {
+          name: escapeExpression(source.name),
+          path: source.path,
+        });
+    } else if (source?.type === "plugin") {
+      notice +=
+        " " +
+        I18n.t("critical_deprecation.plugin_source", {
+          name: escapeExpression(source.name),
+        });
+    }
+
+    addGlobalNotice(notice, "critical-deprecation", {
+      dismissable: true,
+      dismissDuration: moment.duration(1, "day"),
+      level: "warn",
+    });
+  }
+}