Add Copilot Completions

[Benjamin Christopher Simmonds (benibenj)]

Closes microsoft/vscode#272672

[Copilot]

Pull Request Overview

This PR adds Copilot Completions functionality to the extension by implementing a comprehensive completions system with prompt factory architecture, context management, and integration with OpenAI/Copilot services.

Key changes:

• Implements prompt factories for building completion prompts with workspace context and cascading allocation
• Adds networking infrastructure for communication with Copilot/OpenAI services
• Implements streaming completion processing with SSE support
• Adds language detection, file system utilities, and logging infrastructure

Reviewed Changes

Copilot reviewed 116 out of 275 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
workspaceContextPromptFactory.ts	Factory for building prompts with workspace context using virtual components
componentsCompletionsPromptFactory.tsx	Main declarative prompt factory with JSX-based prompt construction and context resolution
completionsPromptFactory.ts	Core factory interfaces and sequential/timeout handling wrappers
completionsPromptFactory.test.tsx	Comprehensive test suite for prompt factory functionality
cascadingPromptFactory.ts	Base class for cascading prompt allocation across components
asyncUtils.ts	Utilities for handling async operations with cancellation
stream.ts	SSE processor for streaming OpenAI/Copilot API responses
stream.test.ts	Test suite for SSE stream processing
openai.ts	OpenAI API integration with choice handling
model.ts	Model management and selection logic
fetch.ts	HTTP fetching infrastructure for OpenAI endpoints
fetch.test.ts	Tests for fetch and error handling
fetch.fake.ts	Test utilities for mocking fetch operations
config.ts	Configuration for engine/model selection
config.test.ts	Tests for configuration handling
progress.ts	Status reporting infrastructure
postInsertion.ts	Post-insertion tracking and telemetry
notificationSender.ts	User notification abstraction
networkingTypes.ts	Networking type definitions
networking.ts	Core networking fetcher abstraction
networkConfiguration.ts	Network endpoint configuration
logger.ts	Logging infrastructure with telemetry integration
localFileSystem.ts	Local file system implementation
languages.ts	Language definitions and template handling
languageDetection.ts	Language detection from file extensions/names
languageDetection.test.ts	Tests for language detection
generatedLanguages.ts	Generated language metadata from linguist
generatedLanguages.test.ts	Tests for generated languages
inlineCompletion.ts	Inline completion orchestration
radix.ts	LRU radix trie data structure
radix.test.ts	Tests for radix trie
iterableHelpers.ts	Async iterable utility functions
speculativeRequestCache.ts	Cache for speculative completion requests
telemetryNames.ts	Telemetry constant definitions
logging/util.ts	Logging utility functions
telemetryLogSender.ts	Telemetry log sender implementation

[Vijay krishna (vjaykrsna)]

I am glad that you guys did this. I hope open sourcing it will bring greater improvement in less time.
Excited for it ❤️