# messagediff [![Build Status](https://travis-ci.org/d4l3k/messagediff.svg?branch=master)](https://travis-ci.org/d4l3k/messagediff) [![Coverage Status](https://coveralls.io/repos/github/d4l3k/messagediff/badge.svg?branch=master)](https://coveralls.io/github/d4l3k/messagediff?branch=master) [![GoDoc](https://godoc.org/github.com/d4l3k/messagediff?status.svg)](https://godoc.org/github.com/d4l3k/messagediff)

A library for doing diffs of arbitrary Golang structs.

If the unsafe package is available messagediff will diff unexported fields in
addition to exported fields. This is primarily used for testing purposes as it
allows for providing informative error messages.

Optionally, fields in structs can be tagged as `testdiff:"ignore"` to make
messagediff skip it when doing the comparison.


## Example Usage
In a normal file:
```go
package main

import "gopkg.in/d4l3k/messagediff.v1"

type someStruct struct {
    A, b int
    C []int
}

func main() {
    a := someStruct{1, 2, []int{1}}
    b := someStruct{1, 3, []int{1, 2}}
    diff, equal := messagediff.PrettyDiff(a, b)
    /*
        diff =
        `added: .C[1] = 2
        modified: .b = 3`

        equal = false
    */
}

```
In a test:
```go
import "gopkg.in/d4l3k/messagediff.v1"

...

type someStruct struct {
    A, b int
    C []int
}

func TestSomething(t *testing.T) {
    want := someStruct{1, 2, []int{1}}
    got := someStruct{1, 3, []int{1, 2}}
    if diff, equal := messagediff.PrettyDiff(want, got); !equal {
        t.Errorf("Something() = %#v\n%s", got, diff)
    }
}
```
To ignore a field in a struct, just annotate it with testdiff:"ignore" like
this:
```go
package main

import "gopkg.in/d4l3k/messagediff.v1"

type someStruct struct {
    A int
    B int `testdiff:"ignore"`
}

func main() {
    a := someStruct{1, 2}
    b := someStruct{1, 3}
    diff, equal := messagediff.PrettyDiff(a, b)
    /*
        equal = true
        diff = ""
    */
}
```

See the `DeepDiff` function for using the diff results programmatically.

## License
Copyright (c) 2015 [Tristan Rice](https://fn.lc) <rice@fn.lc>

messagediff is licensed under the MIT license. See the LICENSE file for more information.

bypass.go and bypasssafe.go are borrowed from
[go-spew](https://github.com/davecgh/go-spew) and have a seperate copyright
notice.