add config option HighlightValues for adding colour/color to output

spew/common.go

@@ -62,6 +62,11 @@ var (
 	closeMapBytes         = []byte("]")
 	lenEqualsBytes        = []byte("len=")
 	capEqualsBytes        = []byte("cap=")
+	highlight1StartBytes  = []byte("\x1b[32m")
+	highlight2StartBytes  = []byte("\x1b[33m")
+	highlight3StartBytes  = []byte("\x1b[34m")
+	highlight4StartBytes  = []byte("\x1b[36m")
+	highlightEndBytes     = []byte("\x1b[0m")
 )
 
 // hexDigits is used to map a decimal value to a hex digit.

spew/config.go

@@ -98,6 +98,10 @@ type ConfigState struct {
 	// be spewed to strings and sorted by those strings.  This is only
 	// considered if SortKeys is true.
 	SpewKeys bool
+
+	// HighlightValues adds colour/color to scalar values in output.
+	// The colours are suitable for ANSI displays.
+	HighlightValues bool
 }
 
 // Config is the active configuration of the top-level functions.

spew/doc.go

@@ -118,6 +118,10 @@ The following configuration options are available:
 		spewed to strings and sorted by those strings.  This is only
 		considered if SortKeys is true.
 
+	* HighlightValues
+		When true, values in dumps are highlighted using colours/colors
+		suitable for ANSI-compatible displays.
+
 Dump Usage
 
 Simply call spew.Dump with a list of variables you want to dump:

spew/dump.go

@@ -309,6 +309,26 @@ func (d *dumpState) dump(v reflect.Value) {
 		}
 	}
 
+	highlightIsOn := false
+	if d.cs.HighlightValues {
+		switch kind {
+		case reflect.String:
+			highlightIsOn = true
+			d.w.Write(highlight1StartBytes)
+		case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int,
+			reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint,
+			reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
+			highlightIsOn = true
+			d.w.Write(highlight2StartBytes)
+		case reflect.Bool:
+			highlightIsOn = true
+			d.w.Write(highlight3StartBytes)
+		case reflect.Uintptr:
+			highlightIsOn = true
+			d.w.Write(highlight4StartBytes)
+		}
+	}
+
 	switch kind {
 	case reflect.Invalid:
 		// Do nothing.  We should never get here since invalid has already
@@ -446,6 +466,10 @@ func (d *dumpState) dump(v reflect.Value) {
 			fmt.Fprintf(d.w, "%v", v.String())
 		}
 	}
+
+	if highlightIsOn {
+		d.w.Write(highlightEndBytes)
+	}
 }
 
 // fdump is a helper function to consolidate the logic from the various public

spew/dump_test.go

@@ -1040,3 +1040,43 @@ func TestDumpSortedKeys(t *testing.T) {
 	}
 
 }
+
+func TestDumpHighlightValues(t *testing.T) {
+	cfg := spew.ConfigState{HighlightValues: true}
+	colBytes := map[string]string{
+		"reset": "\x1b[0m",
+		"str":   "\x1b[32m",
+		"num":   "\x1b[33m",
+		"bool":  "\x1b[34m",
+		"other": "\x1b[36m",
+	}
+	s := cfg.Sdump(map[int]string{1: "1", 3: "3", 2: "2"})
+	expected := "(map[int]string) (len=3) {\n" +
+		"(int) " + colBytes["num"] + "1" + colBytes["reset"] + ": (string) (len=1) " + colBytes["str"] + "\"1\"" + colBytes["reset"] + ",\n" +
+		"(int) " + colBytes["num"] + "3" + colBytes["reset"] + ": (string) (len=1) " + colBytes["str"] + "\"3\"" + colBytes["reset"] + ",\n" +
+		"(int) " + colBytes["num"] + "2" + colBytes["reset"] + ": (string) (len=1) " + colBytes["str"] + "\"2\"" + colBytes["reset"] + "\n" +
+		"}\n"
+	if s != expected {
+		t.Errorf("Highlighted string mismatch:\n  %v %v", s, expected)
+	}
+
+	s = cfg.Sdump(map[stringer]int{"1": 1, "3": 3, "2": 2})
+	expected = "(map[spew_test.stringer]int) (len=3) {\n" +
+		"(spew_test.stringer) (len=1) stringer 1: (int) " + colBytes["num"] + "1" + colBytes["reset"] + ",\n" +
+		"(spew_test.stringer) (len=1) stringer 3: (int) " + colBytes["num"] + "3" + colBytes["reset"] + ",\n" +
+		"(spew_test.stringer) (len=1) stringer 2: (int) " + colBytes["num"] + "2" + colBytes["reset"] + "\n" +
+		"}\n"
+	if s != expected {
+		t.Errorf("Highlighted ints mismatch:\n  %v %v", s, expected)
+	}
+
+	s = cfg.Sdump(map[string]bool{"custom1": true, "custom2": false})
+	expected = "(map[string]bool) (len=2) {\n" +
+		"(string) (len=7) " + colBytes["str"] + `"custom1"` + colBytes["reset"] + ": (bool) " + colBytes["bool"] + "true" + colBytes["reset"] + ",\n" +
+		"(string) (len=7) " + colBytes["str"] + `"custom2"` + colBytes["reset"] + ": (bool) " + colBytes["bool"] + "false" + colBytes["reset"] + "\n" +
+		"}\n"
+	if s != expected {
+		t.Errorf("Highlighted keys mismatch:\n  %v %v", s, expected)
+	}
+
+}