steverusso / go-udiff

µDiff - a micro Go diff library

µDiff

Micro diff (µDiff) is a Go library that implements the Myers' diffing algorithm. It aims to provide a minimal API to compute and apply diffs with zero dependencies. It also supports generating diffs in the Unified Format. If you are looking for a way to parse unified diffs, check out sourcegraph/go-diff.

This is merely a copy of the Golang tools internal diff package with a few modifications to export package symbols. All credit goes to the Go authors.

Usage

You can import the package using the following command:

go get github.com/aymanbagabas/go-udiff

Examples

Generate a unified diff for strings a and b.

package main

import (
    "fmt"

    "github.com/aymanbagabas/go-udiff"
    "github.com/aymanbagabas/go-udiff/myers"
)

func main() {
    a := "Hello, world!\n"
    b := "Hello, Go!\nSay hi to µDiff"
    edits := myers.ComputeEdits(a, b)
    unified, _ := udiff.ToUnified("a.txt", "b.txt", a, edits)
    fmt.Println(unified)
}

--- a.txt
+++ b.txt
@@ -1 +1,2 @@
-Hello, world!
+Hello, Go!
+Say hi to µDiff
\ No newline at end of file

Apply changes to a string.

package main

import (
    "fmt"

    "github.com/aymanbagabas/go-udiff"
    "github.com/aymanbagabas/go-udiff/myers"
)

func main() {
    a := "Hello, world!\n"
    b := "Hello, Go!\nSay hi to µDiff"

    edits := myers.ComputeEdits(a, b)
    final, err := udiff.Apply(a, edits)
    if err != nil {
        panic(err)
    }

    fmt.Println(final)
}

Hello, Go!
Say hi to µDiff

To get a line-by-line diff and edits:

package main

import (
    "fmt"

    "github.com/aymanbagabas/go-udiff"
    "github.com/aymanbagabas/go-udiff/myers"
)

func main() {
    a := "Hello, world!\n"
    b := "Hello, Go!\nSay hi to µDiff"

    edits := myers.ComputeEdits(a, b)
    d, err := udiff.ToUnifiedDiff("a.txt", "b.txt", a, edits)
    if err != nil {
        panic(err)
    }

    for _, h := range d.Hunks {
        fmt.Printf("hunk: -%d, +%d\n", h.FromLine, h.ToLine)
        for _, l := range h.Lines {
            fmt.Printf("%s %q\n", l.Kind, l.Content)
        }
    }
}

hunk: -1, +1
delete "Hello, world!\n"
insert "Hello, Go!\n"
insert "Say hi to µDiff"

Alternatives

• sergi/go-diff No longer reliable. See #123 and #141.
• hexops/gotextdiff Takes the same approach but looks like the project is abandoned.
• sourcegraph/go-diff It doesn't compute diffs. Great package for parsing and printing unified diffs.

Contributing

Please send any contributions upstream. Pull requests made against the upstream diff package are welcome.

License

BSD 3-Clause and MIT.