emptycasevet

README

emptycasevet

A tiny go/analysis vet tool that reports empty non-default case clauses in switch / type switch.

If you intentionally leave a case empty, add at least a comment inside the case body to pass the check.

Install

# Requires Go 1.24+
go install github.com/ivanpointer/emptycasevet/cmd/emptycasevet@latest

Usage

• As a standalone analyzer:

emptycasevet ./...

• With go vet via -vettool:

emptycasevet_path=$(command -v emptycasevet)
GOFLAGS="-vettool=$emptycasevet_path" go vet ./...

• In CI pipelines, add a step (example GitHub Actions):

- name: Install emptycasevet
  run: go install github.com/ivanpointer/emptycasevet/cmd/emptycasevet@latest
- name: Run emptycasevet
  run: emptycasevet ./...

What it flags

• Non-default case with empty body: flagged.
• default with empty body: allowed.
• Non-default case with only a comment: allowed.

Example:

switch x := 1; x {
case 1: // flagged: empty case body; did you mean `case a, b:`?
case 2:
    // ok with comment
default:
    // empty default allowed
}

Library usage (for integrators)

If you want to consume the analyzer programmatically (e.g. for integration in a tool such as golangci-lint), import the package and reference the exported Analyzer:

import emptycasevet "github.com/ivanpointer/emptycasevet"

func init() {
    // register emptycasevet.Analyzer with your driver/runner
    _ = emptycasevet.Analyzer
}

Configuration options

The analyzer supports the following option (via go/analysis flags):

• -allow_header_comment (default: false): Consider an inline comment placed on the same line as the case header as acceptable. By default, only comments in the case body or on the next line(s) after the colon are considered.

Examples:

• Standalone:

  emptycasevet -allow_header_comment ./...
  

• With go vet:

  emptycasevet_path=$(command -v emptycasevet)
  GOFLAGS="-vettool=$emptycasevet_path -emptycase.allow_header_comment" go vet ./...
  

  Note: When used as a -vettool, flags are namespaced by the analyzer name (emptycase).

Notes for adding to golangci-lint

• This repository exposes a public Analyzer at package path github.com/ivanpointer/emptycasevet.
• The CLI binary remains available at github.com/ivanpointer/emptycasevet/cmd/emptycasevet.
• The analyzer is small, has tests via analysistest, and is licensed under the MIT License (see LICENSE).
• When submitting a PR to golangci-lint, wire it similarly to other go/analysis analyzers by importing the package and registering the Analyzer.

Stability, performance, and maintenance

• Stable: small, focused analyzer with a minimal API surface (single exported Analyzer).
• Performance: single-pass AST walk over switch/type switch nodes; no type-checker loading nor heavy allocations.
• Maintenance: unit tests cover both positive and negative cases; semantic versioning will be used for releases.

Documentation

Overview

Package emptycasevet provides a go/analysis Analyzer that reports non-default switch cases with empty bodies.

Index

• Variables

Variables

var Analyzer = &analysis.Analyzer{
	Name: "emptycase",
	Doc:  "reports non-default switch cases with empty bodies",
	Run: func(pass *analysis.Pass) (any, error) {
		for _, f := range pass.Files {
			ast.Inspect(f, func(n ast.Node) bool {
				switch s := n.(type) {
				case *ast.SwitchStmt:
					checkCases(pass, f, s.Body.List)
				case *ast.TypeSwitchStmt:
					checkCases(pass, f, s.Body.List)
				}
				return true
			})
		}
		return nil, nil
	},
	Flags: flag.FlagSet{},
}

Analyzer reports empty non-default case clauses in switch/type switch statements.