Remove support for non-glimmer template-only components

packages/@ember/-internals/environment/lib/env.ts

@@ -66,21 +66,6 @@ export const ENV = {
 
   STRUCTURED_PROFILE: false,
 
-  /**
-    Whether to use Glimmer Component semantics (as opposed to the classic "Curly"
-    components semantics) for template-only components. See RFC #278.
-
-    This is not intended to be set directly, as the implementation may change in
-    the future. Use `@ember/optional-features` instead.
-
-    @property _TEMPLATE_ONLY_GLIMMER_COMPONENTS
-    @for EmberENV
-    @type Boolean
-    @default false
-    @private
-  */
-  _TEMPLATE_ONLY_GLIMMER_COMPONENTS: false,
-
   /**
     Whether to perform extra bookkeeping needed to make the `captureRenderTree`
     API work.

packages/@ember/-internals/glimmer/lib/resolver.ts

@@ -1,5 +1,3 @@
-import { privatize as P } from '@ember/-internals/container';
-import { ENV } from '@ember/-internals/environment';
 import type { InternalFactory, InternalOwner, RegisterOptions } from '@ember/-internals/owner';
 import { isFactory } from '@ember/-internals/owner';
 import { assert } from '@ember/debug';
@@ -274,22 +272,11 @@ export default class ResolverImpl
     let definition: Nullable<ResolvedComponentDefinition> = null;
 
     if (pair.component === null) {
-      if (ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS) {
-        definition = {
-          state: templateOnlyComponent(undefined, name),
-          manager: TEMPLATE_ONLY_COMPONENT_MANAGER,
-          template,
-        };
-      } else {
-        let factory = owner.factoryFor(P`component:-default`)!;
-        let manager = getInternalComponentManager(factory.class as object);
-
-        definition = {
-          state: factory,
-          manager,
-          template,
-        };
-      }
+      definition = {
+        state: templateOnlyComponent(undefined, name),
+        manager: TEMPLATE_ONLY_COMPONENT_MANAGER,
+        template,
+      };
     } else {
       let factory = pair.component;
       assert(`missing component class ${name}`, factory.class !== undefined);

packages/@ember/-internals/glimmer/lib/setup-registry.ts

@@ -1,9 +1,7 @@
 import type { Registry } from '@ember/-internals/container';
 import { privatize as P } from '@ember/-internals/container';
-import { ENV } from '@ember/-internals/environment';
 import { getOwner } from '@ember/-internals/owner';
 import { assert } from '@ember/debug';
-import Component from './component';
 import Input from './components/input';
 import LinkTo from './components/link-to';
 import Textarea from './components/textarea';
@@ -53,8 +51,4 @@ export function setupEngineRegistry(registry: Registry): void {
 
   registry.register('component:link-to', LinkTo);
   registry.register('component:textarea', Textarea);
-
-  if (!ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS) {
-    registry.register(P`component:-default`, Component);
-  }
 }

packages/@ember/-internals/glimmer/tests/integration/application/debug-render-tree-test.ts

@@ -55,19 +55,6 @@ if (ENV._DEBUG_RENDER_TREE) {
   moduleFor(
     'Application test: debug render tree',
     class extends ApplicationTestCase {
-      _TEMPLATE_ONLY_GLIMMER_COMPONENTS: boolean;
-
-      constructor(assert: QUnit['assert']) {
-        super(assert);
-        this._TEMPLATE_ONLY_GLIMMER_COMPONENTS = ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-        ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = true;
-      }
-
-      teardown() {
-        super.teardown();
-        ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = this._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-      }
-
       async '@test routes'() {
         this.addTemplate('index', 'Index');
         this.addTemplate('foo', 'Foo {{outlet}}');

packages/@ember/-internals/glimmer/tests/integration/application/hot-reload-test.js

@@ -1,6 +1,5 @@
 import { moduleFor, ApplicationTestCase, strip, runTask } from 'internal-test-helpers';
 
-import { ENV } from '@ember/-internals/environment';
 import Service, { service } from '@ember/service';
 import { Component, Helper } from '@ember/-internals/glimmer';
 import { expect } from '@glimmer/util';
@@ -13,9 +12,6 @@ moduleFor(
   class extends ApplicationTestCase {
     constructor() {
       super(...arguments);
-      this._TEMPLATE_ONLY_GLIMMER_COMPONENTS = ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-
-      ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = true;
 
       let didCreateReloader = (reloader) => {
         this.reloader = reloader;
@@ -77,11 +73,6 @@ moduleFor(
       );
     }
 
-    teardown() {
-      super.teardown();
-      ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = this._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-    }
-
     hotReload(name, template) {
       let reloader = expect(this.reloader);
       let revision = (reloader.revisionFor(name) || 0) + 1;

packages/@ember/-internals/glimmer/tests/integration/components/angle-bracket-invocation-test.js

@@ -1,6 +1,5 @@
 import { moduleFor, RenderingTestCase, strip, classes, runTask } from 'internal-test-helpers';
 import { setModifierManager, modifierCapabilities } from '@glimmer/manager';
-import { ENV } from '@ember/-internals/environment';
 import EmberObject from '@ember/object';
 
 import { set, setProperties } from '@ember/object';
@@ -1166,17 +1165,6 @@ moduleFor(
 moduleFor(
   'AngleBracket Invocation (splattributes)',
   class extends RenderingTestCase {
-    constructor() {
-      super(...arguments);
-      this._TEMPLATE_ONLY_GLIMMER_COMPONENTS = ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-      ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = true;
-    }
-
-    teardown() {
-      super.teardown();
-      ENV._TEMPLATE_ONLY_GLIMMER_COMPONENTS = this._TEMPLATE_ONLY_GLIMMER_COMPONENTS;
-    }
-
     registerComponent(name, template) {
       super.registerComponent(name, { template, ComponentClass: null });
     }