emptycasevet

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.

Why this exists

Accidentally leaving a non-default case empty is easy when refactoring a switch (e.g., splitting values across cases or removing code). This linter nudges you to either:

• Merge values into a single case (e.g., case a, b:), or
• Leave an intentional comment in the case body to document that it's deliberately empty.

Type switch example

type T interface{}

func g(v T) {
    switch v.(type) {
    case int: // flagged: empty case body; did you mean `case a, b:`?
    case string:
        // ok: intentional, documented
    default:
        // default may be empty
    }
}

Exit status

• Exits with code 0 if no issues are found
• Exits with code >0 (non-zero) if any diagnostics are reported This makes it safe to use in CI to fail builds when empty cases are detected.

Go compatibility

• Requires Go 1.24+
• Developed and tested with Go 1.24.x
• Uses the standard go/analysis API and does not rely on unstable internals

Contributing

Contributions are welcome! Please:

• Open an issue describing the improvement or bug.
• Include tests for behavior changes.
• Keep the analyzer minimal and focused to reduce false positives and runtime overhead.

Releases

Stable releases are tagged using semantic versioning (v0.x.y initially). Use a tagged version in CI for reproducible builds:

go install github.com/ivanpointer/emptycasevet/cmd/[email protected]

If you don’t need pinning, @latest is fine for local use.