---
phase: 06-sql-consolidation-code-quality
plan: 02
subsystem: codegen
tags: [go-ast, codegen, typescript, go-generate, lefthook]

# Dependency graph
requires: []
provides:
  - Go→TypeScript event constant generator (genevents)
  - go:generate directive for automatic event sync
  - LibraryConfigChanged gap automatically fixed
  - Pre-commit codegen-check hook covers event constants
affects: [frontend, backend-events]

# Tech tracking
tech-stack:
  added: [go/ast, go/parser, go/token]
  patterns: [AST-based codegen for cross-language constant sync, atomic file writes via temp+rename]

key-files:
  created:
    - backend/events/cmd/genevents/main.go
  modified:
    - backend/events/events.go
    - frontend/src/events.ts

key-decisions:
  - "Iterate f.Decls directly (not map) for deterministic declaration-order output"
  - "Strip trailing period from Go doc comments for cleaner TypeScript comments"
  - "Atomic writes via temp file + os.Rename to prevent partial output"

patterns-established:
  - "Cross-language constant sync: Go source of truth → go/ast parser → TypeScript codegen"
  - "go:generate directive per package with relative paths to output"

requirements-completed: [QUAL-02]

# Metrics
duration: 2min
completed: 2026-03-05
---

# Phase 06 Plan 02: Event Codegen Summary

**Go→TypeScript event constant generator using go/ast, fixing LibraryConfigChanged gap and wiring pre-commit drift detection**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-05T00:20:57Z
- **Completed:** 2026-03-05T00:23:43Z
- **Tasks:** 2
- **Files modified:** 3

## Accomplishments
- Built `genevents` codegen tool parsing Go AST for deterministic TypeScript output
- Fixed missing `LibraryConfigChanged` constant — now automatically generated from Go source
- Verified codegen-check pre-commit hook detects drift when Go constants change without regenerating TS
- All 21 event constants synced between Go and TypeScript, frontend typecheck passes

## Task Commits

Each task was committed atomically:

1. **Task 1: Create event codegen tool** - `3e9edd0` (feat)
2. **Task 2: Wire codegen-check pre-commit hook** - No changes needed (lefthook.yml already correctly configured; task was verification-only)

## Files Created/Modified
- `backend/events/cmd/genevents/main.go` - Go→TypeScript event constant generator using go/ast
- `backend/events/events.go` - Added `//go:generate` directive for automatic codegen
- `frontend/src/events.ts` - Regenerated with all 21 constants including LibraryConfigChanged

## Decisions Made
- Iterated `f.Decls` directly (not collected into map) for deterministic declaration-order output
- Stripped trailing periods from Go doc comments for cleaner TypeScript comments
- Used atomic writes (temp file + `os.Rename`) to prevent partial output on failure
- No lefthook.yml changes needed — existing `codegen-check` hook already runs `go generate ./...` which now includes the event generator

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Event codegen complete, ready for remaining Phase 6 plans
- Pre-commit hook validates all generated code (templ, sqlc, events) in <2 seconds

## Self-Check: PASSED

---
*Phase: 06-sql-consolidation-code-quality*
*Completed: 2026-03-05*