unassignederr

unassignederr is a tool for checking for returned errors which have been left unassigned or uninitialized.

Golang draws a distinction betweens a between a nil and a nil interface. This behaviour has been well documented in the Golang FAQ. It's something that easily could be missed. This linting rule is intended to highlight cases where you may accidentally return an error struct that hasn't been initialized.

Bad 😿

type NaughtyErr struct {
      Msg string
}

func (e *NaughtyErr) Error() string { return e.Msg }

func returnsError() error {
      var err *NaughtyErr

      return err // err is unassigned
}

Better 😸

func returnsError() error {
      var err *NaughtyErr

      if doSomething() == false {
            err = &NaughtyErr{Msg: "error message"}
      }

      return err // err is correctly assigned
}

Install

go get -u github.com/Jesse-Cameron/unassignederr

Usage

nil_error_struct: A tool for identifying when a uninitialised error struct is being incorrectly returned.

Usage: nil_error_struct [-flag] [package]


Flags:
  -V    print version and exit
  -all
        no effect (deprecated)
  -c int
        display offending line with this many lines of context (default -1)
  -cpuprofile string
        write CPU profile to this file
  -debug string
        debug flags, any subset of "fpstv"
  -fix
        apply all suggested fixes
  -flags
        print analyzer flags in JSON
  -json
        emit JSON output
  -memprofile string
        write memory profile to this file
  -source
        no effect (deprecated)
  -tags string
        no effect (deprecated)
  -trace string
        write trace log to this file
  -v    no effect (deprecated)

Examples

$ unassignederr ./...

$ unassignederr github.com/package_name

go/analysis

The package provides Analyzer instance that can be used with go/analysis API.