DEV: Allow registering a widget shim which renders using hbs (#20177)

This is an alternative way to use `RenderGlimmer` which can be more ergonomic for iterative updates of a codebase. For documentation, see `widgets/render-glimmer.js`

app/assets/javascripts/discourse/app/widgets/render-glimmer.js

@@ -2,6 +2,7 @@ import templateOnly from "@ember/component/template-only";
 import { setComponentTemplate } from "@ember/component";
 import { tracked } from "@glimmer/tracking";
 import { assert } from "@ember/debug";
+import { createWidgetFrom } from "discourse/widgets/widget";
 
 /*
 
@@ -89,7 +90,9 @@ export default class RenderGlimmer {
       template.name === "factory"
     );
     this.renderInto = renderInto;
-    this.widget = widget;
+    if (widget) {
+      this.widget = widget;
+    }
     this.template = template;
     this.data = data;
   }
@@ -108,7 +111,9 @@ export default class RenderGlimmer {
 
   destroy() {
     if (this._componentInfo) {
-      this.widget._findView().unmountChildComponent(this._componentInfo);
+      this.parentMountWidgetComponent.unmountChildComponent(
+        this._componentInfo
+      );
     }
   }
 
@@ -132,7 +137,7 @@ export default class RenderGlimmer {
   }
 
   connectComponent() {
-    const { element, template, widget } = this;
+    const { element, template } = this;
 
     const component = templateOnly();
     component.name = "Widgets/RenderGlimmer";
@@ -143,9 +148,39 @@ export default class RenderGlimmer {
       component,
       @tracked data: this.data,
     };
-    const parentMountWidgetComponent = widget._findView();
-    parentMountWidgetComponent.mountChildComponent(this._componentInfo);
+
+    this.parentMountWidgetComponent.mountChildComponent(this._componentInfo);
+  }
+
+  get parentMountWidgetComponent() {
+    return this.widget?._findView() || this._emberView;
   }
 }
 
 RenderGlimmer.prototype.type = "Widget";
+
+/**
+ * Define a widget shim which renders a Glimmer template. Designed for incrementally migrating
+ * a widget-based UI to Glimmer. Widget attrs will be made available to your template at `@data`.
+ * For more details, see documentation for the RenderGlimmer class.
+ * @param name - the widget's name (which can then be used in `.attach` elsewhere)
+ * @param tagName - a string describing a new wrapper element (e.g. `div.my-class`)
+ * @param template - a glimmer template compiled via ember-cli-htmlbars
+ */
+export function registerWidgetShim(name, tagName, template) {
+  const RenderGlimmerShim = class MyClass extends RenderGlimmer {
+    constructor(attrs) {
+      super(null, tagName, template, attrs);
+      return this;
+    }
+
+    get widget() {
+      return this.parentWidget;
+    }
+
+    didRenderWidget() {}
+    willRerenderWidget() {}
+  };
+
+  createWidgetFrom(RenderGlimmerShim, name, {});
+}

app/assets/javascripts/discourse/app/widgets/widget.js

@@ -30,6 +30,10 @@ export function queryRegistry(name) {
   return _registry[name];
 }
 
+export function deleteFromRegistry(name) {
+  return delete _registry[name];
+}
+
 const _decorators = {};
 
 export function decorateWidget(widgetName, cb) {

app/assets/javascripts/discourse/tests/integration/components/widgets/render-glimmer-test.js

@@ -4,9 +4,11 @@ import { setupRenderingTest } from "discourse/tests/helpers/component-test";
 import { click, fillIn, render } from "@ember/test-helpers";
 import { hbs } from "ember-cli-htmlbars";
 import widgetHbs from "discourse/widgets/hbs-compiler";
-import Widget from "discourse/widgets/widget";
+import Widget, { deleteFromRegistry } from "discourse/widgets/widget";
 import ClassicComponent from "@ember/component";
-import RenderGlimmer from "discourse/widgets/render-glimmer";
+import RenderGlimmer, {
+  registerWidgetShim,
+} from "discourse/widgets/render-glimmer";
 import { bind } from "discourse-common/utils/decorators";
 
 class DemoWidget extends Widget {
@@ -126,12 +128,18 @@ module("Integration | Component | Widget | render-glimmer", function (hooks) {
     this.registry.register("widget:demo-widget", DemoWidget);
     this.registry.register("widget:toggle-demo-widget", ToggleDemoWidget);
     this.registry.register("component:demo-component", DemoComponent);
+    registerWidgetShim(
+      "render-glimmer-test-shim",
+      "div.my-wrapper",
+      hbs`<span class='shim-content'>{{@data.attr1}}</span>`
+    );
   });
 
   hooks.afterEach(function () {
     this.registry.unregister("widget:demo-widget");
     this.registry.unregister("widget:toggle-demo-widget");
     this.registry.unregister("component:demo-component");
+    deleteFromRegistry("render-glimmer-test-shim");
   });
 
   test("argument handling", async function (assert) {
@@ -310,4 +318,13 @@ module("Integration | Component | Widget | render-glimmer", function (hooks) {
     await click(".toggleButton");
     assert.strictEqual(query("div.glimmer-wrapper").innerText, "One");
   });
+
+  test("registerWidgetShim can register a fake widget", async function (assert) {
+    await render(
+      hbs`<MountWidget @widget="render-glimmer-test-shim" @args={{hash attr1="val1"}} />`
+    );
+
+    assert.dom("div.my-wrapper span.shim-content").exists();
+    assert.dom("div.my-wrapper span.shim-content").hasText("val1");
+  });
 });