messagediff

README

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:

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:

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:

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 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 and have a seperate copyright notice.

Documentation

Index

• Constants
• func PrettyDiff(a, b interface{}) (string, bool)
• type Diff
  • func DeepDiff(a, b interface{}) (*Diff, bool)
• type MapKey
  • func (n MapKey) String() string
• type Path
  • func (p Path) String() string
• type PathNode
• type SliceIndex
  • func (n SliceIndex) String() string
• type StructField
  • func (n StructField) String() string

Constants

const (
	// UnsafeDisabled is a build-time constant which specifies whether or
	// not access to the unsafe package is available.
	UnsafeDisabled = false
)

Functions

func PrettyDiff

func PrettyDiff(a, b interface{}) (string, bool)

PrettyDiff does a deep comparison and returns the nicely formated results.

Types

type Diff

type Diff struct {
	Added, Removed, Modified map[*Path]interface{}
	// contains filtered or unexported fields
}

Diff represents a change in a struct.

func DeepDiff

func DeepDiff(a, b interface{}) (*Diff, bool)

DeepDiff does a deep comparison and returns the results.

type MapKey

type MapKey struct {
	Key interface{}
}

MapKey is a path element representing a key of a map.

func (MapKey) String

func (n MapKey) String() string

type Path

type Path []PathNode

Path represents a path to a changed datum.

func (Path) String

func (p Path) String() string

type PathNode

type PathNode interface {
	String() string
}

PathNode represents one step in the path.

type SliceIndex

type SliceIndex int

SliceIndex is a path element representing a index of a slice.

func (SliceIndex) String

func (n SliceIndex) String() string

type StructField

type StructField string

StructField is a path element representing a field of a struct.

func (StructField) String

func (n StructField) String() string