DEV: Unsilence this-property-fallback deprecation (#29855)

This one has the potential to be very noisy, so a special dedupliation handler is introduced.

https://meta.discourse.org/t/337276

app/assets/javascripts/discourse-common/addon/deprecation-workflow.js

@@ -1,8 +1,4 @@
 const DEPRECATION_WORKFLOW = [
-  {
-    handler: "silence",
-    matchId: "ember-this-fallback.this-property-fallback",
-  },
   { handler: "silence", matchId: "discourse.select-kit" },
   {
     handler: "silence",

app/assets/javascripts/discourse/app/initializers/deprecation-this-property-fallback-handler.js

@@ -0,0 +1,44 @@
+import { registerDeprecationHandler } from "@ember/debug";
+import { consolePrefix, getThemeInfo } from "discourse/lib/source-identifier";
+
+let registered = false;
+const seenMessages = new Set();
+
+export default {
+  initialize() {
+    if (registered) {
+      return;
+    }
+
+    registerDeprecationHandler((message, options, next) => {
+      if (options.id !== "ember-this-fallback.this-property-fallback") {
+        return;
+      }
+
+      // These errors don't have useful backtraces, but we can parse theme/plugin
+      // info from the message itself.
+      const pluginMatch = message.match(/\/plugins\/([\w-]+)\//)?.[1];
+      const themeIdMatch = message.match(/\/theme-(\d+)\//)?.[1];
+
+      if (pluginMatch || themeIdMatch) {
+        const source = {
+          type: pluginMatch ? "plugin" : "theme",
+          name: pluginMatch || getThemeInfo(parseInt(themeIdMatch, 10)),
+          id: themeIdMatch,
+        };
+        options.source = source;
+        message = `${consolePrefix(null, source)} ${message}`;
+      }
+
+      // Only print each message once, to avoid flood of console noise
+      if (seenMessages.has(message)) {
+        return;
+      }
+      seenMessages.add(message);
+      options.url = "https://meta.discourse.org/t/337276";
+      next(message, options);
+    });
+
+    registered = true;
+  },
+};

app/assets/javascripts/discourse/app/lib/highlight-syntax.js

@@ -1,4 +1,4 @@
-import DEBUG from "@glimmer/env";
+import { DEBUG } from "@glimmer/env";
 import { waitForPromise } from "@ember/test-waiters";
 import mergeHTMLPlugin from "discourse/lib/highlight-syntax-merge-html-plugin";
 import { isTesting } from "discourse-common/config/environment";

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

@@ -1,3 +1,4 @@
+import { DEBUG } from "@glimmer/env";
 import { registerDeprecationHandler } from "@ember/debug";
 import Service, { service } from "@ember/service";
 import { addGlobalNotice } from "discourse/components/global-notice";
@@ -19,9 +20,13 @@ export const CRITICAL_DEPRECATIONS = [
   "discourse.plugin-outlet-tag-name",
   "discourse.plugin-outlet-parent-view",
   "discourse.d-button-action-string",
-  /^(?!discourse\.)/, // All unsilenced ember deprecations
 ];
 
+if (DEBUG) {
+  // used in system specs
+  CRITICAL_DEPRECATIONS.push("fake-deprecation");
+}
+
 // Deprecation handling APIs don't have any way to unregister handlers, so we set up permanent
 // handlers and link them up to the application lifecycle using module-local state.
 let handler;