assert: switch the diff library to go-diff

assert/assertions.go

@@ -12,13 +12,15 @@ import (
 	"regexp"
 	"runtime"
 	"runtime/debug"
+	"strconv"
 	"strings"
 	"time"
 	"unicode"
 	"unicode/utf8"
 
+	"github.com/sergi/go-diff/diffmatchpatch"
+
 	"github.com/davecgh/go-spew/spew"
-	"github.com/pmezard/go-difflib/difflib"
 	"gopkg.in/yaml.v3"
 )
 
@@ -145,8 +147,6 @@ func copyExportedFields(expected interface{}) interface{} {
 // structures.
 //
 // This function does no assertion of any kind.
-//
-// Deprecated: Use [EqualExportedValues] instead.
 func ObjectsExportedFieldsAreEqual(expected, actual interface{}) bool {
 	expectedCleaned := copyExportedFields(expected)
 	actualCleaned := copyExportedFields(actual)
@@ -1777,6 +1777,10 @@ func typeAndKind(v interface{}) (reflect.Type, reflect.Kind) {
 	return t, k
 }
 
+type diffOptions struct {
+	ColoredOutput bool
+}
+
 // diff returns a diff of both values as long as both are of the same type and
 // are a struct, map, slice, array or string. Otherwise it returns an empty string.
 func diff(expected interface{}, actual interface{}) string {
@@ -1808,18 +1812,79 @@ func diff(expected interface{}, actual interface{}) string {
 		e = spewConfig.Sdump(expected)
 		a = spewConfig.Sdump(actual)
 	}
+	structuredDiff := structuredDiff(e, a)
+	prettyDiff := prettyDiff(structuredDiff)
+	return "\n\nDiff:\n" + prettyDiff
+}
+
+func structuredDiff(e string, a string) []diffmatchpatch.Diff {
+	dmp := diffmatchpatch.New()
+	fromRunes, toRunes, runesToLines := dmp.DiffLinesToRunes(e, a)
+	diffs := dmp.DiffMainRunes(fromRunes, toRunes, false)
+	hydrated := make([]diffmatchpatch.Diff, 0, len(diffs))
+	for _, aDiff := range diffs {
+		chars := strings.FieldsFunc(aDiff.Text, func(r rune) bool {
+			return string(r) == diffmatchpatch.IndexSeparator
+		})
+		text := make([]string, len(chars))
+
+		for i, char := range chars {
+			i1, err := strconv.Atoi(char)
+			if err == nil {
+				text[i] = runesToLines[i1]
+			}
+		}
+		for idx, line := range text {
+			if aDiff.Type == diffmatchpatch.DiffEqual && idx < len(text)-1 {
+				continue
+			}
+			hydrated = append(hydrated, diffmatchpatch.Diff{
+				Type: aDiff.Type,
+				Text: line,
+			})
+		}
+	}
+	return hydrated
+}
 
-	diff, _ := difflib.GetUnifiedDiffString(difflib.UnifiedDiff{
-		A:        difflib.SplitLines(e),
-		B:        difflib.SplitLines(a),
-		FromFile: "Expected",
-		FromDate: "",
-		ToFile:   "Actual",
-		ToDate:   "",
-		Context:  1,
-	})
+func prettyDiff(diffs []diffmatchpatch.Diff) string {
+	var diff strings.Builder
 
-	return "\n\nDiff:\n" + diff
+	diff.WriteString("--- Expected\n+++ Actual\n")
+
+	for _, diffChunk := range diffs {
+		switch diffChunk.Type {
+		case diffmatchpatch.DiffInsert:
+			// Make sure the different parts are on separate lines for better readability
+			// i.e. it makes diffs like +got-expected to go as +got\n-expected\n
+			if !strings.HasSuffix(diffChunk.Text, "\n") {
+				diffChunk.Text = diffChunk.Text + "\n"
+			}
+			_, _ = fmt.Fprintf(&diff, "+%s", diffChunk.Text)
+		case diffmatchpatch.DiffDelete:
+			// Make sure the different parts are on separate lines for better readability
+			// i.e. it makes diffs like +got-expected to go as +got\n-expected\n
+			if !strings.HasSuffix(diffChunk.Text, "\n") {
+				diffChunk.Text = diffChunk.Text + "\n"
+			}
+			_, _ = fmt.Fprintf(&diff, "-%s", diffChunk.Text)
+		default:
+			if len(diffChunk.Text) == 0 {
+				continue
+			}
+			equalTextByLines := strings.SplitAfter(diffChunk.Text, "\n")
+			var linesTrimmed []string
+			for _, line := range equalTextByLines {
+				if len(line) == 0 {
+					continue
+				}
+				linesTrimmed = append(linesTrimmed, line)
+			}
+			// We're not interested in the equal parts, so only keep the last line for some context
+			_, _ = fmt.Fprintf(&diff, " %s", equalTextByLines[len(linesTrimmed)-1])
+		}
+	}
+	return diff.String()
 }
 
 func isFunction(arg interface{}) bool {

assert/assertions_test.go

@@ -385,11 +385,10 @@ func TestEqualExportedValues(t *testing.T) {
 	            	Diff:
 	            	--- Expected
 	            	+++ Actual
-	            	@@ -3,3 +3,3 @@
 	            	  Exported2: (assert.Nested) {
 	            	-  Exported: (int) 2,
 	            	+  Exported: (int) 1,
-	            	   notExported: (interface {}) <nil>`,
+	            	 }`,
 		},
 		{
 			value1:        S3{&Nested{1, 2}, &Nested{3, 4}},
@@ -399,11 +398,10 @@ func TestEqualExportedValues(t *testing.T) {
 	            	Diff:
 	            	--- Expected
 	            	+++ Actual
-	            	@@ -2,3 +2,3 @@
 	            	  Exported1: (*assert.Nested)({
 	            	-  Exported: (int) 1,
 	            	+  Exported: (string) (len=1) "a",
-	            	   notExported: (interface {}) <nil>`,
+	            	 }`,
 		},
 		{
 			value1: S4{[]*Nested{
@@ -419,11 +417,10 @@ func TestEqualExportedValues(t *testing.T) {
 	            	Diff:
 	            	--- Expected
 	            	+++ Actual
-	            	@@ -7,3 +7,3 @@
 	            	   (*assert.Nested)({
 	            	-   Exported: (int) 3,
 	            	+   Exported: (int) 2,
-	            	    notExported: (interface {}) <nil>`,
+	            	 }`,
 		},
 		{
 			value1:        S{[2]int{1, 2}, Nested{2, 3}, 4, Nested{5, 6}},
@@ -656,7 +653,7 @@ func TestStringEqual(t *testing.T) {
 		msgAndArgs []interface{}
 		want       string
 	}{
-		{equalWant: "hi, \nmy name is", equalGot: "what,\nmy name is", want: "\tassertions.go:\\d+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"hi, \\\\nmy name is\"\n\\s+actual\\s+: \"what,\\\\nmy name is\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+@@ -1,2 \\+1,2 @@\n\\s+-hi, \n\\s+\\+what,\n\\s+my name is"},
+		{equalWant: "hi, \nmy name is", equalGot: "what,\nmy name is", want: "\tassertions.go:\\d+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"hi, \\\\nmy name is\"\n\\s+actual\\s+: \"what,\\\\nmy name is\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+-hi, \n\\s+\\+what,\n\\s+my name is"},
 	} {
 		mockT := &bufferT{}
 		Equal(mockT, currCase.equalWant, currCase.equalGot, currCase.msgAndArgs...)
@@ -671,10 +668,10 @@ func TestEqualFormatting(t *testing.T) {
 		msgAndArgs []interface{}
 		want       string
 	}{
-		{equalWant: "want", equalGot: "got", want: "\tassertions.go:\\d+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+@@ -1 \\+1 @@\n\\s+-want\n\\s+\\+got\n"},
-		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{"hello, %v!", "world"}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+@@ -1 \\+1 @@\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+hello, world!\n"},
-		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{123}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+@@ -1 \\+1 @@\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+123\n"},
-		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{struct{ a string }{"hello"}}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+@@ -1 \\+1 @@\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+{a:hello}\n"},
+		{equalWant: "want", equalGot: "got", want: "\tassertions.go:\\d+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+-want\n\\s+\\+got\n"},
+		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{"hello, %v!", "world"}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+hello, world!\n"},
+		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{123}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+123\n"},
+		{equalWant: "want", equalGot: "got", msgAndArgs: []interface{}{struct{ a string }{"hello"}}, want: "\tassertions.go:[0-9]+: \n\t+Error Trace:\t\n\t+Error:\\s+Not equal:\\s+\n\\s+expected: \"want\"\n\\s+actual\\s+: \"got\"\n\\s+Diff:\n\\s+-+ Expected\n\\s+\\++ Actual\n\\s+-want\n\\s+\\+got\n\\s+Messages:\\s+{a:hello}\n"},
 	} {
 		mockT := &bufferT{}
 		Equal(mockT, currCase.equalWant, currCase.equalGot, currCase.msgAndArgs...)
@@ -2301,7 +2298,6 @@ func TestDiff(t *testing.T) {
 Diff:
 --- Expected
 +++ Actual
-@@ -1,3 +1,3 @@
  (struct { foo string }) {
 - foo: (string) (len=5) "hello"
 + foo: (string) (len=3) "bar"
@@ -2318,7 +2314,6 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -2,5 +2,5 @@
   (int) 1,
 - (int) 2,
   (int) 3,
@@ -2338,11 +2333,10 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -2,4 +2,4 @@
   (int) 1,
 - (int) 2,
-- (int) 3
 + (int) 3,
+- (int) 3
 + (int) 5
  }
 `
@@ -2357,14 +2351,13 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -1,6 +1,6 @@
  (map[string]int) (len=4) {
 - (string) (len=4) "four": (int) 4,
 + (string) (len=4) "five": (int) 5,
   (string) (len=3) "one": (int) 1,
 - (string) (len=5) "three": (int) 3,
-- (string) (len=3) "two": (int) 2
 + (string) (len=5) "seven": (int) 7,
+- (string) (len=3) "two": (int) 2
 + (string) (len=5) "three": (int) 3
  }
 `
@@ -2380,7 +2373,6 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -1,3 +1,3 @@
  (*errors.errorString)({
 - s: (string) (len=19) "some expected error"
 + s: (string) (len=12) "actual error"
@@ -2398,7 +2390,6 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -2,3 +2,3 @@
   A: (string) (len=11) "some string",
 - B: (int) 10
 + B: (int) 15
@@ -2416,10 +2407,8 @@ Diff:
 Diff:
 --- Expected
 +++ Actual
-@@ -1,2 +1,2 @@
 -(time.Time) 2020-09-24 00:00:00 +0000 UTC
 +(time.Time) 2020-09-25 00:00:00 +0000 UTC
- 
 `
 
 	actual = diff(

go.mod

@@ -7,6 +7,7 @@ go 1.17
 require (
 	github.com/davecgh/go-spew v1.1.1
 	github.com/pmezard/go-difflib v1.0.0
+	github.com/sergi/go-diff v1.3.1
 	github.com/stretchr/objx v0.5.1
 	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -1,10 +1,23 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sergi/go-diff v1.3.1 h1:xkr+Oxo4BOQKmkn/B9eMK0g5Kg/983T9DqqPHwYqD+8=
+github.com/sergi/go-diff v1.3.1/go.mod h1:aMJSSKb2lpPvRNec0+w3fl7LP9IOFzdc9Pa4NFbPK1I=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.5.1 h1:4VhoImhV/Bm0ToFkXFi8hXNXwpDRZ/ynw3amt82mzq0=
 github.com/stretchr/objx v0.5.1/go.mod h1:/iHQpkQwBD6DLUmQ4pE+s1TXdob1mORJ4/UFdrifcy0=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=