Add compat adapter for ember-get-config

packages/compat/src/compat-adapters/ember-get-config.ts

@@ -0,0 +1,29 @@
+import V1Addon from '../v1-addon';
+import writeFile from 'broccoli-file-creator';
+import { join } from 'path';
+
+function createIndexContents(config: any): string {
+  return `export default ${JSON.stringify(config)};`;
+}
+
+/**
+ * The `ember-get-config` addon conceptually does just one thing: re-exports the `config/environment` runtime module
+ * from the host app so that addons can import it themseles. It handles the "hard part" of knowing what the host app's
+ * module name is, since that's not something an addon can normally know ahead of time.
+ *
+ * From a dependency graph perspective though, declaring all of the dependencies correctly would require a circular
+ * dependency from the addon back to the host app itself, which we don't want to introduce.
+ *
+ * We need to basically re-implement the entire addon's behavior so that it still exports the app's
+ * `config/environment` runtime value, but without needing it to actually export from the host app's module.
+ */
+export default class extends V1Addon {
+  get v2Tree() {
+    const configModulePath = join(this.app.root, 'config/environment.js');
+    // eslint-disable-next-line @typescript-eslint/no-require-imports
+    const configModule = require(configModulePath);
+    const appEnvironmentConfig = configModule(this.app.env);
+
+    return writeFile('index.js', createIndexContents(appEnvironmentConfig));
+  }
+}

packages/compat/src/v1-addon.ts

@@ -113,7 +113,7 @@ export default class V1Addon {
   constructor(
     protected addonInstance: any,
     protected addonOptions: Required<Options>,
-    private app: V1App,
+    protected app: V1App,
     private packageCache: PackageCache,
     private orderIdx: number
   ) {