= err113 image:https://godoc.org/github.com/Djarvur/go-err113?status.svg["GoDoc",link="http://godoc.org/github.com/Djarvur/go-err113"] image:https://travis-ci.org/Djarvur/go-err113.svg["Build Status",link="https://travis-ci.org/Djarvur/go-err113"] image:https://coveralls.io/repos/Djarvur/go-err113/badge.svg?branch=master&service=github["Coverage Status",link="https://coveralls.io/github/Djarvur/go-err113?branch=master"] Daniel Podolsky :toc:

Golang linter to check the errors handling expressions

== Details

Starting from Go 1.13 the standard error type behaviour was changed: one error could be derived from another with fmt.Errorf() method using %w format specifier.

So the errors hierarchy could be built for flexible and responsible errors processing.

And to make this possible at least two simple rules should be followed:

1. error values should not be compared directly but with errors.Is() method.
2. error should not be created dynamically from scratch but by the wrapping the static (package-level) error.

This linter is checking the code for these 2 rules compliance.

=== Reports

So, err113 reports every == and != comparison for exact error type variables except comparison to nil and io.EOF.

Also, any call of errors.New() and fmt.Errorf() methods are reported except the calls used to initialise package-level variables and the fmt.Errorf() calls wrapping the other errors.

Note: non-standard packages, like github.com/pkg/errors are ignored completely.

== Install

go get -u github.com/Djarvur/go-err113/cmd/err113

== Usage

Defined by link:https://pkg.go.dev/golang.org/x/tools/go/analysis/singlechecker[singlechecker] package.

err113: checks the error handling rules according to the Go 1.13 new error type

Usage: err113 [-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)

== Thanks

To link:https://github.com/quasilyte[Iskander (Alex) Sharipov] for the really useful advices.

To link:https://github.com/jackwhelpton[Jack Whelpton] for the bugfix provided.