Go Diff Linter

Lint only the code you changed, not the entire codebase. Formatters are applied automatically, Claude fixes lint issues manually.

Quick Start

bash

# Run linting and auto-format for changes vs develop branch
.claude/skills/go-diff-linter/scripts/run_lint.sh develop

# Report saved to .golangci-diff/report.md

What It Does

•Extracts changed files - Gets diff between your branch and base branch
•Runs linters - Only on packages containing changed files (avoids unrelated errors)
•Filters issues - Keeps only issues within changed line ranges
•Auto-formats - Applies gofumpt and goimports to all changed files
•Generates report - Markdown report for Claude to fix remaining lint issues

Workflow

Step 1: Run the Script

bash

.claude/skills/go-diff-linter/scripts/run_lint.sh <base_branch> [-o report.md]

Example:

bash

.claude/skills/go-diff-linter/scripts/run_lint.sh develop
.claude/skills/go-diff-linter/scripts/run_lint.sh main -o my-report.md

Step 2: Review Changes

Formatters are applied automatically. Check with:

bash

git status
git diff

Step 3: Fix Lint Issues

Read the report: .golangci-diff/report.md

Report contains:

•Changed files and line ranges
•Each lint issue: file, line, linter, description, current code, suggested fix

Fix each issue using the Edit tool. Only modify lines specified in the report.

Config

Always uses skill's assets/.golangci.yml for consistent linting (project config is temporarily backed up and restored).

Enabled Linters:

•Essential: govet, staticcheck, errcheck, ineffassign, unused, typecheck
•Security: gosec
•Bug prevention: bodyclose, nilerr, sqlclosecheck, contextcheck, rowserrcheck
•Code quality: gocritic, revive, misspell, errorlint, dupl, goconst, cyclop

Auto-applied Formatters:

•gofumpt (with extra-rules)
•goimports

Key Behaviors

Type	Scope	Action
Lint issues	Changed lines only	Claude manually fixes
Formatting	Changed files	Auto-applied
Unchanged code	Skip	Never touch

Example Report Output

markdown

## Summary

- Total issues from linter: 15
- Lint issues in changed lines: 12
- Filtered out (unchanged code): 3
- Formatting: automatically applied

## Lint Issues (Must Fix)

### `pkg/handler/api.go`

**Line 42:5** - [gosec] Security issue
> G104: Errors unhandled

Current code:
```go
42: json.Unmarshal(data, &result)

Suggested fix:

if err := json.Unmarshal(data, &result); err != nil {
    return err
}

code


## Requirements

- Go 1.21+
- golangci-lint v2.x (uses `--output.json.path` and `golangci-lint fmt`)
- Python 3.10+
- jq