Add compat adapter for @ember/test-waiters

packages/compat/src/compat-adapters/@ember/test-waiters.ts

@@ -0,0 +1,24 @@
+import V1Addon from '../../v1-addon';
+import { satisfies } from 'semver';
+
+export default class extends V1Addon {
+  // our heuristic for detecting tree suppression can't deal with the way
+  // test-waiters patches treeFor on other copies of its addon instances all
+  // over the place. It causes us to falsely detect that it's trying to suppress
+  // all tree output, reducing in empty copies.
+  protected suppressesTree(_name: string): boolean {
+    return false;
+  }
+
+  reduceInstances(instances: V1Addon[]): V1Addon[] {
+    if (!satisfies(this.packageJSON.version, '>=3.0.2')) {
+      throw new Error(
+        `@ember/test-waiters cannot work safely under embroider before version 3.0.2 due to https://github.com/emberjs/ember-test-waiters/pull/388. You have a copy at version ${this.packageJSON.version}.`
+      );
+    }
+
+    // we know test waiters tries to dedup itself, so there's no point in building
+    // and smooshing many copies.
+    return [instances[0]];
+  }
+}

packages/compat/src/v1-addon.ts

@@ -615,7 +615,7 @@ export default class V1Addon {
   // But there is a very common use case that we *can* handle opportunisticaly,
   // which is a treeFor() that's used purely to guard whether `_super` will be
   // called or not.
-  private suppressesTree(name: string): boolean {
+  protected suppressesTree(name: string): boolean {
     if (!this.customizes('treeFor')) {
       return false;
     }

packages/router/package.json

@@ -30,7 +30,7 @@
     "prepack": "rollup --config"
   },
   "dependencies": {
-    "@ember/test-waiters": "^3.0.0",
+    "@ember/test-waiters": "^3.0.2",
     "@embroider/addon-shim": "workspace:^"
   },
   "devDependencies": {