Fix experiment lookup

chat-lib/test/nesProvider.spec.ts

@@ -27,13 +27,17 @@ import { CopilotToken } from '../src/_internal/platform/authentication/common/co
 
 
 class TestFetcher implements IFetcher {
+
+	requests: { url: string; options: FetchOptions }[] = [];
+
 	constructor(private readonly responses: Record<string, string>) { }
 
 	getUserAgentLibrary(): string {
 		return 'test-fetcher';
 	}
 
 	async fetch(url: string, options: FetchOptions): Promise<Response> {
+		this.requests.push({ url, options });
 		const uri = URI.parse(url);
 		const responseText = this.responses[uri.path];
 
@@ -132,18 +136,25 @@ describe('NESProvider Facade', () => {
 		doc.setSelection([new OffsetRange(1, 1)], undefined);
 		const telemetrySender = new TestTelemetrySender();
 		const logTarget = new TestLogTarget();
+		const fetcher = new TestFetcher({ '/chat/completions': await fs.readFile(path.join(__dirname, 'nesProvider.reply.txt'), 'utf8') });
 		const nextEditProvider = createNESProvider({
 			workspace,
-			fetcher: new TestFetcher({ '/chat/completions': await fs.readFile(path.join(__dirname, 'nesProvider.reply.txt'), 'utf8') }),
+			fetcher,
 			copilotTokenManager: new TestCopilotTokenManager(),
 			telemetrySender,
 			logTarget,
 		});
+		nextEditProvider.updateTreatmentVariables({
+			'config.github.copilot.chat.advanced.inlineEdits.xtabProvider.defaultModelConfigurationString': '{ "modelName": "xtab-test" }',
+		});
 
 		doc.applyEdit(StringEdit.insert(11, '3D'));
 
 		const result = await nextEditProvider.getNextEdit(doc.id.toUri(), CancellationToken.None);
 
+		assert.strictEqual(fetcher.requests.length, 1);
+		assert.strictEqual(fetcher.requests[0].options.json?.model, 'xtab-test');
+
 		assert(result.result);
 
 		const { range, newText } = result.result;

src/platform/configuration/common/defaultsOnlyConfigurationService.ts

@@ -30,6 +30,26 @@ export class DefaultsOnlyConfigurationService extends AbstractConfigurationServi
 	}
 
 	override getExperimentBasedConfig<T extends ExperimentBasedConfigType>(key: ExperimentBasedConfig<T>, experimentationService: IExperimentationService, scope?: ConfigurationScope): T {
+		if (key.experimentName) {
+			const expValue = experimentationService.getTreatmentVariable<Exclude<T, undefined>>(key.experimentName);
+			if (expValue !== undefined) {
+				return expValue;
+			}
+		}
+
+		// This is the pattern we've been using for a while now. We need to maintain it for older experiments.
+		const expValue = experimentationService.getTreatmentVariable<Exclude<T, undefined>>(`copilotchat.config.${key.id}`);
+		if (expValue !== undefined) {
+			return expValue;
+		}
+
+		// This is the pattern vscode uses for settings using the `onExp` tag. But vscode only supports it for
+		// settings defined in package.json, so this is why we're also reading the value from exp here.
+		const expValue2 = experimentationService.getTreatmentVariable<Exclude<T, undefined>>(`config.${key.fullyQualifiedId}`);
+		if (expValue2 !== undefined) {
+			return expValue2;
+		}
+
 		return this.getDefaultValue(key);
 	}