Implement MCP server for AI-assisted migration authoring #74
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FEATURE: Add MCP server with JSON-RPC 2.0 protocol over stdio
This implements the full MCP server infrastructure for tern:
Phase 1 - Foundation:
- Create src/mcp/ module structure with error types and protocol handling
- Implement JSON-RPC 2.0 message parsing and routing
- Implement stdio transport layer for newline-delimited JSON
- Add 'tern mcp' CLI subcommand
- Implement MCP initialize, ping, and capability negotiation
Phase 2 - Resources:
- Implement tern://schema resource for current schema introspection
- Implement tern://migrations resource for listing migrations
- Implement tern://migration/{id} resource for migration details
Phase 3 - PGLite Integration:
- Implement lazy database initialization for sessions
- Use SchemaExporter to set up base state in session databases
- Enable namespace extraction via PostgresCatalog
Phase 4 - Session Management:
- Implement Session and SessionManager types
- Add start_session, cancel_session, list_sessions tools
Phase 5 - Session Operations:
- Implement execute_sql tool with full PGLite integration
- Implement get_session_schema tool for schema introspection
- Implement get_session_diff tool for comparing against base state
- Add apply_operation tool stub for structured operations
- Add generate_migration tool stub for migration generation
The MCP server enables AI assistants to:
- Read current schema and migration history
- Start isolated migration authoring sessions
- Execute SQL against in-memory PostgreSQL (PGLite)
- Compare schema changes and generate migrations
This reverts commit ad62af2.
CHORE: Workaround for pglite_oxide creating files in cwd instead of OS tempdir
FEATURE: Add complete implementations for schema mutation and migration generation - Implement apply_operation with operation parsing, SQL rendering via PostgresRenderer, execution against PGLite session database, and operation history tracking - Implement generate_migration with full diff-to-migration pipeline: loads current schema from session's PGLite, diffs against base state, detects breaking changes, creates Migration object, saves via backend - Both tools require pglite feature; non-pglite versions return appropriate error messages
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FEATURE: Add MCP server with JSON-RPC 2.0 protocol over stdio
This implements the full MCP server infrastructure for tern:
Phase 1 - Foundation:
Phase 2 - Resources:
Phase 3 - PGLite Integration:
Phase 4 - Session Management:
Phase 5 - Session Operations:
The MCP server enables AI assistants to: