Remove deprecations

docs/app/app.ts

@@ -12,7 +12,7 @@ if (macroCondition(isDevelopingApp())) {
 }
 
 setConfig({
-  rootElement: config.APP['rootElement'] as string | undefined,
+  rootElement: config.APP['rootElement'] as string,
 });
 
 export default class App extends Application {

src/components/basic-dropdown-wormhole.gts

@@ -1,47 +1,13 @@
 import Component from '@glimmer/component';
-import { getOwner } from '@ember/owner';
-import { config as utilConfig, _configSet, type Config } from '../config.ts';
-import { deprecate } from '@ember/debug';
+import { getConfig } from '../config.ts';
 
 export interface BasicDropdownWormholeSignature {
   Element: HTMLElement;
 }
 
 export default class BasicDropdownWormholeComponent extends Component<BasicDropdownWormholeSignature> {
   get getDestinationId(): string {
-    let config = utilConfig;
-
-    if (!_configSet) {
-      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-      // @ts-ignore
-      // eslint-disable-next-line @typescript-eslint/no-unsafe-call
-      const configEnvironment = getOwner(this).resolveRegistration(
-        'config:environment',
-      ) as {
-        'ember-basic-dropdown'?: Config;
-      };
-
-      if (configEnvironment['ember-basic-dropdown']) {
-        const legacyConfigString = JSON.stringify(
-          configEnvironment['ember-basic-dropdown'],
-        );
-        deprecate(
-          `You have configured \`ember-basic-dropdown\` in \`ember-cli-build.js\`. Remove that configuration and instead use \`import { setConfig } from 'ember-basic-dropdown/config'; setConfig(${legacyConfigString});`,
-          false,
-          {
-            for: 'ember-basic-dropdown',
-            id: 'ember-basic-dropdown.config-environment',
-            since: {
-              enabled: '8.9',
-              available: '8.9',
-            },
-            until: '9.0.0',
-          },
-        );
-
-        config = configEnvironment['ember-basic-dropdown'];
-      }
-    }
+    const config = getConfig();
 
     return config.destination || 'ember-basic-dropdown-wormhole';
   }

src/components/basic-dropdown.gts

@@ -3,15 +3,13 @@ import { tracked } from '@glimmer/tracking';
 import { action } from '@ember/object';
 import { guidFor } from '@ember/object/internals';
 import calculatePosition from '../utils/calculate-position.ts';
-import { getOwner } from '@ember/owner';
 import { schedule } from '@ember/runloop';
 import { hash } from '@ember/helper';
 import BasicDropdownTrigger from './basic-dropdown-trigger.gts';
 import BasicDropdownContent from './basic-dropdown-content.gts';
 import { or } from 'ember-truth-helpers';
-import { deprecate } from '@ember/debug';
 import { isTesting } from '@embroider/macros';
-import { config as utilConfig, _configSet, type Config } from '../config.ts';
+import { getConfig } from '../config.ts';
 import type Owner from '@ember/owner';
 import type { ComponentLike } from '@glint/template';
 import type {
@@ -97,7 +95,6 @@ export interface BasicDropdownArgs<
   destination?: string;
   destinationElement?: HTMLElement;
   disabled?: boolean;
-  dropdownId?: string;
   rootEventType?: TRootEventType;
   preventScroll?: boolean;
   matchTriggerWidth?: boolean;
@@ -137,8 +134,7 @@ export default class BasicDropdown<
   private dropdownElement: HTMLElement | null = null;
 
   private _uid = guidFor(this);
-  private _dropdownId: string =
-    this.args.dropdownId || `ember-basic-dropdown-content-${this._uid}`;
+  private _dropdownId: string = `ember-basic-dropdown-content-${this._uid}`;
   private _previousDisabled = UNINITIALIZED;
   private _actions: DropdownActions = {
     open: this.open.bind(this),
@@ -228,22 +224,6 @@ export default class BasicDropdown<
     if (this.args.registerAPI) {
       this.args.registerAPI(this.publicAPI);
     }
-
-    if (this.args.dropdownId !== undefined) {
-      deprecate(
-        'You have passed `@dropdownId` into `ember-basic-dropdown`. This property does not work correctly without custom modifiers and is undocumented. Remove this parameter and use the `uniqueId` property from the public API instead.',
-        false,
-        {
-          for: 'ember-basic-dropdown',
-          id: 'ember-basic-dropdown.deprecate-arg-dropdown-id',
-          since: {
-            enabled: '8.8',
-            available: '8.8',
-          },
-          until: '9.0.0',
-        },
-      );
-    }
   }
 
   override willDestroy(): void {
@@ -436,60 +416,7 @@ export default class BasicDropdown<
   }
 
   _getDestinationId(): string {
-    let config = utilConfig;
-
-    if (!_configSet) {
-      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
-      // @ts-ignore
-      // eslint-disable-next-line @typescript-eslint/no-unsafe-call
-      const configEnvironment = getOwner(this).resolveRegistration(
-        'config:environment',
-      ) as {
-        APP: {
-          rootElement: string;
-        };
-        'ember-basic-dropdown': Config;
-      };
-
-      if (configEnvironment['ember-basic-dropdown']) {
-        const legacyConfigString = JSON.stringify(
-          configEnvironment['ember-basic-dropdown'],
-        );
-        deprecate(
-          `You have configured \`ember-basic-dropdown\` in \`ember-cli-build.js\`. Remove that configuration and instead use \`import { setConfig } from 'ember-basic-dropdown/config'; setConfig(${legacyConfigString});`,
-          false,
-          {
-            for: 'ember-basic-dropdown',
-            id: 'ember-basic-dropdown.config-environment',
-            since: {
-              enabled: '8.9',
-              available: '8.9',
-            },
-            until: '9.0.0',
-          },
-        );
-
-        config = configEnvironment['ember-basic-dropdown'];
-      }
-
-      if (configEnvironment['APP']?.rootElement) {
-        deprecate(
-          `ember-basic-dropdown received the \`APP.rootElement\` value from \`ember-cli-build.js\`. You now need to pass this value using \`import { setConfig } from 'ember-basic-dropdown/config'; setConfig({rootElement: config.APP['rootElement']});`,
-          false,
-          {
-            for: 'ember-basic-dropdown',
-            id: 'ember-basic-dropdown.config-environment',
-            since: {
-              enabled: '8.9',
-              available: '8.9',
-            },
-            until: '9.0.0',
-          },
-        );
-
-        config.rootElement = configEnvironment['APP']?.rootElement;
-      }
-    }
+    const config = getConfig();
 
     if (isTesting()) {
       // document doesn't exist in fastboot apps, for this reason we need this check

src/config.ts

@@ -1,16 +1,31 @@
 export interface Config {
   destination?: string;
-  rootElement?: string;
+  rootElement: string;
 }
 
-let _config: Config = {};
+let _config: Config = {
+  rootElement: '',
+};
 
-// This will be removed in next major, don't use this outside the package!
-let _configSet = false;
+let configSet = false;
 
 export function setConfig(config: Config) {
+  if (!config.rootElement) {
+    throw new Error(
+      "ember-basic-dropdown: 'rootElement' is required in the config. See installation instructions for more details.",
+    );
+  }
+
   _config = config;
-  _configSet = true;
+  configSet = true;
 }
 
-export { _config as config, _configSet };
+export function getConfig(): Config {
+  if (!configSet) {
+    throw new Error(
+      'ember-basic-dropdown: setConfig was not called before accessing config. See installation instructions for more details.',
+    );
+  }
+
+  return _config;
+}