[refactor]: working on unit tests for the `FilePromptContentsProvider`

src/vs/base/common/decorators.ts

@@ -127,3 +127,5 @@ export function throttle<T>(delay: number, reducer?: IDebounceReducer<T>, initia
 		};
 	});
 }
+
+export { cancelPreviousCalls } from './decorators/cancelPreviousCalls.js';

src/vs/editor/test/common/codecs/linesDecoder.test.ts

@@ -9,6 +9,7 @@ import { Range } from '../../../common/core/range.js';
 import { VSBuffer } from '../../../../base/common/buffer.js';
 import { newWriteableStream } from '../../../../base/common/stream.js';
 import { Line } from '../../../common/codecs/linesCodec/tokens/line.js';
+import { BaseDecoder } from '../../../../base/common/codecs/baseDecoder.js';
 import { NewLine } from '../../../common/codecs/linesCodec/tokens/newLine.js';
 import { CarriageReturn } from '../../../common/codecs/linesCodec/tokens/carriageReturn.js';
 import { LinesDecoder, TLineToken } from '../../../common/codecs/linesCodec/linesDecoder.js';
@@ -159,6 +160,11 @@ suite('LinesDecoder', () => {
 				"Must return an instance of the original decoder.",
 			);
 
+			assert(
+				transformed instanceof BaseDecoder,
+				"Must return an instance of the base decoder.",
+			);
+
 			setTimeout(() => {
 				stream.write(VSBuffer.fromString('hello\nworld\r\nhow ☁️ are\n\nyou\rdoing\n\n'));
 

src/vs/workbench/contrib/chat/common/promptContentProviders/filePromptContentsProvider.ts

@@ -34,7 +34,7 @@ export class FilePromptContentProvider extends PromptContentsProviderBase<FileCh
 				}
 
 				// if file was deleted, forward the event to
-				// the `getContentsStream` produce an error
+				// the `getContentsStream()` produce an error
 				if (event.contains(this.uri, FileChangeType.DELETED)) {
 					return this.onChangeEmitter.fire(event);
 				}

src/vs/workbench/contrib/chat/common/promptContentProviders/textModelContentsProvider.ts

@@ -15,6 +15,9 @@ import { IModelContentChangedEvent } from '../../../../../editor/common/textMode
  * Prompt contents provider for a {@linkcode ITextModel} instance.
  */
 export class TextModelContentsProvider extends PromptContentsProviderBase<IModelContentChangedEvent> {
+	/**
+	 * URI component of the prompt associated with this contents provider.
+	 */
 	public readonly uri = this.model.uri;
 
 	constructor(

src/vs/workbench/contrib/chat/test/common/promptContentProviders/filePromptContentsProvider.test.ts

@@ -0,0 +1,95 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { ReadableStream } from '../../../../../../base/common/stream.js';
+import { URI } from '../../../../../../base/common/uri.js';
+import { IFileService } from '../../../../../../platform/files/common/files.js';
+import { FileService } from '../../../../../../platform/files/common/fileService.js';
+import { NullPolicyService } from '../../../../../../platform/policy/common/policy.js';
+import { ILogService, NullLogService } from '../../../../../../platform/log/common/log.js';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../../base/test/common/utils.js';
+import { IConfigurationService } from '../../../../../../platform/configuration/common/configuration.js';
+import { ConfigurationService } from '../../../../../../platform/configuration/common/configurationService.js';
+import { TestInstantiationService } from '../../../../../../platform/instantiation/test/common/instantiationServiceMock.js';
+import { VSBuffer } from '../../../../../../base/common/buffer.js';
+import { randomInt } from '../../../../../../base/common/numbers.js';
+import { FilePromptContentProvider } from '../../../common/promptContentProviders/filePromptContentsProvider.js';
+import { Line } from '../../../../../../editor/common/codecs/linesCodec/tokens/line.js';
+import { BaseDecoder } from '../../../../../../base/common/codecs/baseDecoder.js';
+import { InMemoryFileSystemProvider } from '../../../../../../platform/files/common/inMemoryFilesystemProvider.js';
+import { Schemas } from '../../../../../../base/common/network.js';
+
+suite('FilePromptContentsProvider', function () {
+	const testDisposables = ensureNoDisposablesAreLeakedInTestSuite();
+
+	let instantiationService: TestInstantiationService;
+	setup(async () => {
+		const nullPolicyService = new NullPolicyService();
+		const nullLogService = testDisposables.add(new NullLogService());
+		const nullFileService = testDisposables.add(new FileService(nullLogService));
+		const nullConfigService = testDisposables.add(new ConfigurationService(
+			URI.file('/config.json'),
+			nullFileService,
+			nullPolicyService,
+			nullLogService,
+		));
+		instantiationService = testDisposables.add(new TestInstantiationService());
+
+		const fileSystemProvider = testDisposables.add(new InMemoryFileSystemProvider());
+		testDisposables.add(nullFileService.registerProvider(Schemas.file, fileSystemProvider));
+
+		instantiationService.stub(IFileService, nullFileService);
+		instantiationService.stub(ILogService, nullLogService);
+		instantiationService.stub(IConfigurationService, nullConfigService);
+	});
+
+	test('provides contents of a file', async function () {
+		const fileService = instantiationService.get(IFileService);
+
+		const fileName = `file-${randomInt(10000)}.prompt.md`;
+		const fileUri = URI.file(`/${fileName}`);
+
+		if (await fileService.exists(fileUri)) {
+			await fileService.del(fileUri);
+		}
+		await fileService.writeFile(fileUri, VSBuffer.fromString('Hello, world!'));
+		await new Promise((resolve) => setTimeout(resolve, 5));
+
+		const contentsProvider = testDisposables.add(instantiationService.createInstance(
+			FilePromptContentProvider,
+			fileUri,
+		));
+
+		let streamOrError: ReadableStream<Line> | Error | undefined;
+		testDisposables.add(contentsProvider.onContentChanged((event) => {
+			streamOrError = event;
+		}));
+		contentsProvider.start();
+
+		await new Promise((resolve) => setTimeout(resolve, 25));
+
+		assert(
+			streamOrError instanceof BaseDecoder,
+			`Provider must produce a stream of lines, got '${streamOrError}'.`,
+		);
+
+		const stream = testDisposables.add(streamOrError);
+
+		const receivedLines = await stream.consumeAll();
+		assert.strictEqual(
+			receivedLines.length,
+			1,
+			'Must read the correct number of lines from the provider.',
+		);
+
+		const expectedLine = new Line(1, 'Hello, world!');
+		const receivedLine = receivedLines[0];
+		assert(
+			receivedLine.equals(expectedLine),
+			`Expected to receive '${expectedLine}', got '${receivedLine}'.`,
+		);
+	});
+});