# Precheck

> Run pre-commit checks (gofmt, goimports, gazelle, code generators, build) before committing Prysm changes. Required before every commit.

- Skill: `offchainlabs/precheck` (Agent Skill)
- Install (CLI): `npx skillmds@latest add offchainlabs/precheck`
- Raw SKILL.md: https://api.skillmd.com/api/skills/offchainlabs/precheck/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: offchainlabs (https://skillmd.com/u/offchainlabs)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/offchainlabs/precheck

---


# Pre-commit checks

Run these in order from the repo root before every commit. Stop and report if any step fails.

1. **gofmt** — format changed Go files:
   ```bash
   gofmt -l $(git diff --name-only --diff-filter=ACM HEAD | grep '\.go$')
   ```
   If output is non-empty, run `gofmt -w` on those files.

2. **goimports** — organize imports:
   ```bash
   goimports -l $(git diff --name-only --diff-filter=ACM HEAD | grep '\.go$')
   ```
   If output is non-empty, run `goimports -w` on those files.

3. **Gazelle — sync `deps.bzl`** (when `go.mod` changed):
   ```bash
   bazel run //:gazelle -- update-repos -from_file=go.mod -to_macro=deps.bzl%prysm_deps -prune=true
   git diff --exit-code deps.bzl
   ```

4. **Gazelle — sync `BUILD.bazel`**:
   ```bash
   bazel run //:gazelle -- fix --mode=diff
   ```
   If the diff is non-empty, run `bazel run //:gazelle -- fix`.

5. **Regenerate code** (when `.proto`, SSZ-tagged structs, or proto service interfaces changed):
   ```bash
   make gen
   ```
   Regenerates proto/ssz/mocks and runs goimports+gofmt on the generated files. It's cached; if unsure which files changed, bypass the cache with `make gen mode=force`. Limit to one kind with e.g. `make gen proto`.

6. **Build smoke check**:
   ```bash
   make build
   ```
   `make build` runs `gen` first, then builds all binaries.

## Report

- Success: "✅ All pre-checks passed. Ready to commit."
- Failure: name the failed check and the fix command.