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nakedret

nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.

Installation

Install Nakedret via go install:

go install github.com/alexkohler/nakedret/v2/cmd/nakedret@latest

If you have not already added your GOPATH/bin directory to your PATH environment variable then you will need to do so.

Windows (cmd):

set PATH=%PATH%;C:\your\GOPATH\bin

Bash (you can verify a path has been set):

# Check if nakedret is on PATH
which nakedret
export PATH=$PATH:/your/GOPATH/bin #to set path if it does not exist

Usage

Similar to other Go static anaylsis tools (such as golint, go vet), nakedret can be invoked with one or more filenames, directories, or packages named by its import path. Nakedret also supports the ... wildcard.

nakedret [flags] files/directories/packages

Currently, the only flag supported is -l, which is an optional numeric flag to specify the maximum length a function can be (in terms of line length). If not specified, it defaults to 5.

It can also be run using go vet:

go vet -vettool=$(which nakedret) ./...

Purpose

As noted in Go's Code Review comments:

Naked returns are okay if the function is a handful of lines. Once it's a medium sized function, be explicit with your return values. Corollary: it's not worth it to name result parameters just because it enables you to use naked returns. Clarity of docs is always more important than saving a line or two in your function.

This tool aims to catch naked returns on non-trivial functions.

Example

Let's take the types package in the Go source as an example:

$ nakedret -l 25 types/
types/check.go:245 checkFiles naked returns on 26 line function 
types/typexpr.go:443 collectParams naked returns on 53 line function 
types/stmt.go:275 caseTypes naked returns on 27 line function 
types/lookup.go:275 MissingMethod naked returns on 39 line function

Below is one of the not so intuitive uses of naked returns in types/lookup.go found by nakedret (nakedret will return the line number of the last naked return in the function):

func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
	// fast path for common case
	if T.Empty() {
		return
	}

	// TODO(gri) Consider using method sets here. Might be more efficient.

	if ityp, _ := V.Underlying().(*Interface); ityp != nil {
		// TODO(gri) allMethods is sorted - can do this more efficiently
		for _, m := range T.allMethods {
			_, obj := lookupMethod(ityp.allMethods, m.pkg, m.name)
			switch {
			case obj == nil:
				if static {
					return m, false
				}
			case !Identical(obj.Type(), m.typ):
				return m, true
			}
		}
		return
	}

	// A concrete type implements T if it implements all methods of T.
	for _, m := range T.allMethods {
		obj, _, _ := lookupFieldOrMethod(V, false, m.pkg, m.name)

		f, _ := obj.(*Func)
		if f == nil {
			return m, false
		}

		if !Identical(f.typ, m.typ) {
			return m, true
		}
	}

	return
}

TODO

  • Unit tests (may require some refactoring to do correctly)
  • supporting toggling of build.Context.UseAllFiles may be useful for some.
  • Configuration on whether or not to run on test files
  • Vim quickfix format?

Contributing

Pull requests welcome!

Other static analysis tools

If you've enjoyed nakedret, take a look at my other static anaylsis tools!

  • unimport - Finds unnecessary import aliases
  • prealloc - Finds slice declarations that could potentially be preallocated.