Use godebug/diff for Compare

pretty/util.go

 package pretty
 
 import (
-	"bytes"
 	"fmt"
-	"strings"
+
+	"github.com/kylelemons/godebug/diff"
 )
 
 // Print writes the default representation of the given values to standard output.
@@ -24,107 +24,6 @@ func (o *Options) Print(vals ...interface{}) {
 // value with respect to the "want" value.
 func Compare(got, want interface{}) string {
 	diffOpt := &Options{Diffable: true}
-	gotLines := strings.Split(Reflect(got, diffOpt), "\n")
-	wantLines := strings.Split(Reflect(want, diffOpt), "\n")
-
-	chunks := diff(gotLines, wantLines)
-	return diffString(chunks)
-}
-
-type chunk struct {
-	add []string
-	del []string
-	eq  []string
-}
 
-// Diff uses an O(D(N+M)) shortest-edit-script algorithm
-// to compute the difference between A and B.
-//
-// algorithm: http://www.xmailserver.org/diff2.pdf
-func diff(A, B []string) []chunk {
-	N, M := len(A), len(B)
-	MAX := N + M
-	V := make([]int, 2*MAX+1)
-	Vs := make([][]int, 0, 8)
-
-	var D int
-dLoop:
-	for D = 0; D <= MAX; D++ {
-		for k := -D; k <= D; k += 2 {
-			var x int
-			if k == -D || (k != D && V[MAX+k-1] < V[MAX+k+1]) {
-				x = V[MAX+k+1]
-			} else {
-				x = V[MAX+k-1] + 1
-			}
-			y := x - k
-			for x < N && y < M && A[x] == B[y] {
-				x++
-				y++
-			}
-			V[MAX+k] = x
-			if x >= N && y >= M {
-				Vs = append(Vs, append(make([]int, 0, len(V)), V...))
-				break dLoop
-			}
-		}
-		Vs = append(Vs, append(make([]int, 0, len(V)), V...))
-	}
-	fmt.Println(D, N-M)
-	for _, V := range Vs {
-		fmt.Println(V[:MAX-1], V[MAX:MAX+1], V[MAX+1:])
-	}
-	if D == 0 {
-		return nil
-	}
-	chunks := make([]chunk, D+1)
-
-	x, y := N, M
-	for d := D; d > 0; d-- {
-		V := Vs[d]
-		k := x - y
-		insert := k == -d || (k != d && V[MAX+k-1] < V[MAX+k+1])
-
-		x1 := V[MAX+k]
-		var x0, xM, kk int
-		if insert {
-			kk = k + 1
-			x0 = V[MAX+kk]
-			xM = x0
-		} else {
-			kk = k - 1
-			x0 = V[MAX+kk]
-			xM = x0 + 1
-		}
-		y0 := x0 - kk
-
-		var c chunk
-		if insert {
-			c.add = B[y0:][:1]
-		} else {
-			c.del = A[x0:][:1]
-		}
-		c.eq = A[xM:][:x1-xM]
-
-		x, y = x0, y0
-		chunks[d] = c
-	}
-	chunks[0].eq = A[:x]
-	return chunks
-}
-
-func diffString(chunks []chunk) string {
-	buf := new(bytes.Buffer)
-	for _, c := range chunks {
-		for _, line := range c.del {
-			fmt.Fprintf(buf, "-%s\n", line)
-		}
-		for _, line := range c.add {
-			fmt.Fprintf(buf, "+%s\n", line)
-		}
-		for _, line := range c.eq {
-			fmt.Fprintf(buf, " %s\n", line)
-		}
-	}
-	return buf.String()
+	return diff.Diff(Reflect(got, diffOpt), Reflect(want, diffOpt))
 }