Use string formatting for slice of bytes

cmp/cmpopts/example_test.go

@@ -39,7 +39,7 @@ func ExampleIgnoreFields_testing() {
 	//   	SSID:      "CoffeeShopWiFi",
 	// - 	IPAddress: s"192.168.0.2",
 	// + 	IPAddress: s"192.168.0.1",
-	//   	NetMask:   {0xff, 0xff, 0x00, 0x00},
+	//   	NetMask:   s"ffff0000",
 	//   	Clients: []cmpopts_test.Client{
 	//   		... // 3 identical elements
 	//   		{Hostname: "espresso", ...},

cmp/compare_test.go

@@ -1385,6 +1385,24 @@ using the AllowUnexported option.`, "\n"),
 		x:      struct{ X interface{} }{int(0)},
 		y:      struct{ X interface{} }{uint(0)},
 		reason: "mismatched underlying value within interface",
+	}, {
+		label: label + "/SliceOfBytesText",
+		x: [][]byte{
+			[]byte("hello"), []byte("foo"), []byte("barbaz"), []byte("blahdieblah"),
+		},
+		y: [][]byte{
+			[]byte("foo"), []byte("foo"), []byte("barbaz"), []byte("added"), []byte("here"), []byte("hrmph"),
+		},
+		reason: "should print text byte slices as strings",
+	}, {
+		label: label + "/SliceOfBytesBinary",
+		x: [][]byte{
+			[]byte("\xde\xad\xbe\xef"), []byte("\xffoo"), []byte("barbaz"), []byte("blahdieblah"),
+		},
+		y: [][]byte{
+			[]byte("\xffoo"), []byte("foo"), []byte("barbaz"), []byte("added"), []byte("here"), []byte("hrmph\xff"),
+		},
+		reason: "should print text byte slices as strings except those with binary",
 	}}
 }
 

cmp/example_test.go

@@ -37,7 +37,7 @@ func ExampleDiff_testing() {
 	//   	SSID:      "CoffeeShopWiFi",
 	// - 	IPAddress: s"192.168.0.2",
 	// + 	IPAddress: s"192.168.0.1",
-	//   	NetMask:   {0xff, 0xff, 0x00, 0x00},
+	//   	NetMask:   s"ffff0000",
 	//   	Clients: []cmp_test.Client{
 	//   		... // 2 identical elements
 	//   		{Hostname: "macchiato", IPAddress: s"192.168.0.153", LastSeen: s"2009-11-10 23:39:43 +0000 UTC"},

cmp/report_compare.go

@@ -116,7 +116,10 @@ func (opts formatOptions) FormatDiff(v *valueNode, ptrs *pointerReferences) (out
 	}
 
 	// For leaf nodes, format the value based on the reflect.Values alone.
-	if v.MaxDepth == 0 {
+	// As a special case, treat equal []byte as a leaf nodes.
+	isBytes := v.Type.Kind() == reflect.Slice && v.Type.Elem() == reflect.TypeOf(byte(0))
+	isEqualBytes := isBytes && v.NumDiff+v.NumIgnored+v.NumTransformed == 0
+	if v.MaxDepth == 0 || isEqualBytes {
 		switch opts.DiffMode {
 		case diffUnknown, diffIdentical:
 			// Format Equal.

cmp/report_reflect.go

@@ -211,7 +211,7 @@ func (opts formatOptions) FormatValue(v reflect.Value, parentKind reflect.Kind,
 			if len(b) > 0 && utf8.Valid(b) && len(bytes.TrimFunc(b, isPrintSpace)) == 0 {
 				out = opts.formatString("", string(b))
 				skipType = true
-				return opts.WithTypeMode(emitType).FormatType(t, out)
+				return opts.FormatType(t, out)
 			}
 		}
 

cmp/testdata/diffs

@@ -241,9 +241,9 @@
   		"string",
   	}),
   	Bytes: []uint8(Inverse(SplitBytes, [][]uint8{
-  		{0x73, 0x6f, 0x6d, 0x65},
-  		{0x6d, 0x75, 0x6c, 0x74, ...},
-  		{0x6c, 0x69, 0x6e, 0x65},
+  		"some",
+  		"multi",
+  		"line",
   		{
 - 			0x62,
 + 			0x42,
@@ -1158,6 +1158,30 @@
 + 	X: uint(0),
   }
 >>> TestDiff/Reporter/StructFieldAny
+<<< TestDiff/Reporter/SliceOfBytesText
+  [][]uint8{
+- 	"hello",
+  	"foo",
++ 	"foo",
+  	"barbaz",
++ 	"added",
++ 	"here",
+- 	"blahdieblah",
++ 	"hrmph",
+  }
+>>> TestDiff/Reporter/SliceOfBytesText
+<<< TestDiff/Reporter/SliceOfBytesBinary
+  [][]uint8{
+- 	{0xde, 0xad, 0xbe, 0xef},
+  	{0xff, 0x6f, 0x6f},
++ 	"foo",
+  	"barbaz",
++ 	"added",
++ 	"here",
+- 	"blahdieblah",
++ 	{0x68, 0x72, 0x6d, 0x70, 0x68, 0xff},
+  }
+>>> TestDiff/Reporter/SliceOfBytesBinary
 <<< TestDiff/EmbeddedStruct/ParentStructA/Inequal
   teststructs.ParentStructA{
   	privateStruct: teststructs.privateStruct{