Add Copilot Title and Description Provider for PR generation

Author: AobaIwaki123

src/extension.ts

@@ -29,6 +29,7 @@ import { registerBuiltinGitProvider, registerLiveShareGitProvider } from './gitP
 import { GitHubContactServiceProvider } from './gitProviders/GitHubContactServiceProvider';
 import { GitLensIntegration } from './integrations/gitlens/gitlensImpl';
 import { IssueFeatureRegistrar } from './issues/issueFeatureRegistrar';
+import { CopilotTitleAndDescriptionProvider } from './lm/copilotTitleAndDescriptionProvider';
 import { ChatParticipant, ChatParticipantState } from './lm/participants';
 import { registerTools } from './lm/tools/tools';
 import { migrate } from './migrations';
@@ -397,6 +398,11 @@ async function deferredActivate(context: vscode.ExtensionContext, showPRControll
 	const apiImpl = new GitApiImpl(reposManager);
 	context.subscriptions.push(apiImpl);
 
+	// Register Copilot Title and Description Provider
+	Logger.debug('Registering Copilot Title and Description Provider.', 'Activation');
+	const copilotProvider = new CopilotTitleAndDescriptionProvider(credentialStore, telemetry);
+	apiImpl.registerTitleAndDescriptionProvider('Copilot', copilotProvider);
+
 	deferredActivateRegisterBuiltInGitProvider(context, apiImpl, credentialStore);
 
 	Logger.debug('Registering live share git provider.', 'Activation');

src/lm/copilotTitleAndDescriptionProvider.ts

@@ -0,0 +1,251 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import { TitleAndDescriptionProvider } from '../api/api';
+import Logger from '../common/logger';
+import { ITelemetry } from '../common/telemetry';
+import { CredentialStore } from '../github/credentials';
+
+/**
+ * Provides PR title and description generation using VS Code's built-in Copilot language models.
+ * This provider leverages pull request templates when available to generate contextually appropriate
+ * titles and descriptions that follow the repository's conventions.
+ */
+export class CopilotTitleAndDescriptionProvider implements TitleAndDescriptionProvider {
+	private static readonly ID = 'CopilotTitleAndDescriptionProvider';
+
+	constructor(
+		private readonly credentialStore: CredentialStore,
+		private readonly telemetry: ITelemetry
+	) { }
+
+	async provideTitleAndDescription(
+		context: {
+			commitMessages: string[];
+			patches: string[] | { patch: string; fileUri: string; previousFileUri?: string }[];
+			issues?: { reference: string; content: string }[];
+			pullRequestTemplate?: string;
+		},
+		token: vscode.CancellationToken
+	): Promise<{ title: string; description?: string } | undefined> {
+		try {
+			Logger.debug('Starting Copilot PR title and description generation', CopilotTitleAndDescriptionProvider.ID);
+
+			// Select the appropriate language model (use user's preference from all available models)
+			const models = await vscode.lm.selectChatModels();
+			console.log(`Available models: ${models.map(m => `${m.vendor}:${m.family} (${m.name})`).join(', ')}`);
+
+			if (!models || models.length === 0) {
+				Logger.warn('No language models available', CopilotTitleAndDescriptionProvider.ID);
+				return undefined;
+			}
+
+			// Prefer higher capability models for better PR generation
+			// Priority: Claude > GPT-4 > GPT-3.5
+			const model = this.selectBestModel(models);
+			console.log(`Using model: ${model.vendor}:${model.family} (${model.name})`);
+			Logger.debug(`Using model: ${model.vendor}:${model.family} (${model.name})`, CopilotTitleAndDescriptionProvider.ID);
+
+			// Build the prompt
+			const prompt = this.buildPrompt(context);
+			const messages = [vscode.LanguageModelChatMessage.User(prompt)];
+
+			// Send request to language model
+			const response = await model.sendRequest(messages, {
+				justification: 'Generating pull request title and description based on commits and repository templates'
+			}, token);
+
+			// Parse response
+			let responseText = '';
+			for await (const part of response.stream) {
+				if (part instanceof vscode.LanguageModelTextPart) {
+					responseText += part.value;
+				}
+			}
+
+			const result = this.parseResponse(responseText);
+
+			if (result) {
+				Logger.debug(`Generated title: "${result.title}"`, CopilotTitleAndDescriptionProvider.ID);
+				Logger.debug(`Generated description length: ${result.description?.length || 0} characters`, CopilotTitleAndDescriptionProvider.ID);
+
+				// Track telemetry
+				this.telemetry.sendTelemetryEvent('copilot.titleAndDescription.generated', {
+					hasTemplate: context.pullRequestTemplate ? 'true' : 'false',
+					commitCount: context.commitMessages.length.toString(),
+					patchCount: Array.isArray(context.patches) ? context.patches.length.toString() : 'unknown',
+					issueCount: (context.issues?.length || 0).toString(),
+					modelVendor: model.vendor,
+					modelFamily: model.family,
+					modelName: model.name
+				});
+			}
+
+			return result;
+		} catch (error) {
+			Logger.error(`Error generating PR title and description: ${error}`, CopilotTitleAndDescriptionProvider.ID);
+
+			this.telemetry.sendTelemetryEvent('copilot.titleAndDescription.error', {
+				error: error instanceof Error ? error.message : 'unknown'
+			});
+
+			return undefined;
+		}
+	}
+
+	/**
+	 * Selects the best available model for PR generation.
+	 * Prioritizes models based on their capabilities for text generation.
+	 */
+	private selectBestModel(models: readonly vscode.LanguageModelChat[]): vscode.LanguageModelChat {
+		// Define model preference order (higher index = higher preference)
+		const modelPreferences = [
+			// Basic models (lowest priority)
+			{ vendor: 'copilot', family: 'gpt-3.5-turbo', priority: 1 },
+			{ vendor: 'copilot', family: 'gpt-3.5', priority: 1 },
+
+			// Advanced models (medium priority)
+			{ vendor: 'copilot', family: 'gpt-4', priority: 2 },
+			{ vendor: 'copilot', family: 'gpt-4-turbo', priority: 3 },
+			{ vendor: 'copilot', family: 'gpt-4o', priority: 4 },
+			{ vendor: 'copilot', family: 'gpt-4o-mini', priority: 3 },
+
+			// Claude models (highest priority for text generation)
+			{ vendor: 'copilot', family: 'claude-3-haiku', priority: 5 },
+			{ vendor: 'copilot', family: 'claude-3-sonnet', priority: 6 },
+			{ vendor: 'copilot', family: 'claude-3-opus', priority: 7 },
+			{ vendor: 'copilot', family: 'claude-3-5-sonnet', priority: 8 },
+		];
+
+		// Find the highest priority model available
+		let bestModel = models[0];
+		let bestPriority = 0;
+
+		for (const model of models) {
+			const preference = modelPreferences.find(
+				p => p.vendor === model.vendor && p.family === model.family
+			);
+			const priority = preference?.priority || 0;
+
+			if (priority > bestPriority) {
+				bestModel = model;
+				bestPriority = priority;
+			}
+		}
+
+		Logger.debug(
+			`Selected model: ${bestModel.vendor}:${bestModel.family} (priority: ${bestPriority}) from ${models.length} available models`,
+			CopilotTitleAndDescriptionProvider.ID
+		);
+
+		return bestModel;
+	}
+
+	private buildPrompt(context: {
+		commitMessages: string[];
+		patches: string[] | { patch: string; fileUri: string; previousFileUri?: string }[];
+		issues?: { reference: string; content: string }[];
+		pullRequestTemplate?: string;
+	}): string {
+		let prompt = `You are an expert at writing clear, concise pull request titles and descriptions. Please generate a suitable title and description for this pull request based on the provided information.
+
+**Requirements:**
+1. Title should be concise (under 50 characters when possible) and descriptive
+2. Title should follow conventional commit format when appropriate (e.g., "feat:", "fix:", "docs:", etc.)
+3. Description should be comprehensive but focused
+4. If a pull request template is provided, follow its structure and fill in the sections appropriately
+5. Reference any related issues mentioned in commits
+6. Summarize the key changes without being overly technical
+
+`;
+
+		// Add commit information
+		if (context.commitMessages && context.commitMessages.length > 0) {
+			prompt += `**Commit Messages:**\n`;
+			context.commitMessages.forEach((msg, index) => {
+				prompt += `${index + 1}. ${msg}\n`;
+			});
+			prompt += '\n';
+		}
+
+		// Add patch information summary
+		if (context.patches && context.patches.length > 0) {
+			prompt += `**Changes Summary:**\n`;
+			if (Array.isArray(context.patches) && typeof context.patches[0] === 'string') {
+				prompt += `${context.patches.length} file(s) modified\n`;
+			} else {
+				const patchObjects = context.patches as { patch: string; fileUri: string; previousFileUri?: string }[];
+				prompt += `Files modified: ${patchObjects.length}\n`;
+				const fileList = patchObjects.map(p => p.fileUri).slice(0, 10); // Limit to first 10 files
+				prompt += `Key files: ${fileList.join(', ')}${patchObjects.length > 10 ? '...' : ''}\n`;
+			}
+			prompt += '\n';
+		}
+
+		// Add related issues
+		if (context.issues && context.issues.length > 0) {
+			prompt += `**Related Issues:**\n`;
+			context.issues.forEach(issue => {
+				prompt += `- ${issue.reference}: ${issue.content}\n`;
+			});
+			prompt += '\n';
+		}
+
+		// Add pull request template - this is the key part for template integration
+		if (context.pullRequestTemplate) {
+			prompt += `**Pull Request Template to Follow:**\n`;
+			prompt += '```\n' + context.pullRequestTemplate + '\n```\n\n';
+			prompt += `Please structure the description according to this template. Fill in each section with relevant information based on the commits and changes. If a section is not applicable, you may omit it or note "N/A".\n\n`;
+		}
+
+		prompt += `**Output Format:**
+Please respond with the title and description in the following format:
+
+TITLE: [Your generated title here]
+
+DESCRIPTION:
+[Your generated description here]
+
+Make sure the title is on a single line after "TITLE:" and the description follows after "DESCRIPTION:" on subsequent lines.`;
+
+		return prompt;
+	}
+
+	private parseResponse(responseText: string): { title: string; description?: string } | undefined {
+		try {
+			// Look for TITLE: and DESCRIPTION: markers
+			const titleMatch = responseText.match(/TITLE:\s*(.+?)(?=\n|$)/i);
+			const descriptionMatch = responseText.match(/DESCRIPTION:\s*([\s\S]*?)(?=\n\n|$)/i);
+
+			if (!titleMatch) {
+				Logger.warn('Could not parse title from response', CopilotTitleAndDescriptionProvider.ID);
+				return undefined;
+			}
+
+			const title = titleMatch[1].trim();
+			const description = descriptionMatch ? descriptionMatch[1].trim() : undefined;
+
+			// Validate title
+			if (!title || title.length === 0) {
+				Logger.warn('Generated title is empty', CopilotTitleAndDescriptionProvider.ID);
+				return undefined;
+			}
+
+			// Clean up description
+			const cleanDescription = description && description.length > 0
+				? description.replace(/^[\s\n]+|[\s\n]+$/g, '') // Trim whitespace and newlines
+				: undefined;
+
+			return {
+				title,
+				description: cleanDescription
+			};
+		} catch (error) {
+			Logger.error(`Error parsing response: ${error}`, CopilotTitleAndDescriptionProvider.ID);
+			return undefined;
+		}
+	}
+}