config: add SortKeys option to sort native map keys before display

If ConfigState.SortKeys is true, then dump and format will sort map keys
before displaying them. Only native types (bool, ints, uint, uintptr,
string) are supported, other slices are left unchanged.

The motivation is to have more diffable output, mostly for test purpose.

1 files changed, 42 insertions, 0 deletions

diff --git a/spew/dump_test.go b/spew/dump_test.go
index 31b7b6b..354c71c 100644
--- a/spew/dump_test.go
+++ b/spew/dump_test.go
@@ -65,6 +65,7 @@ import (
 	"bytes"
 	"fmt"
 	"github.com/davecgh/go-spew/spew"
+	"reflect"
 	"testing"
 	"unsafe"
 )
@@ -896,3 +897,44 @@ func TestDump(t *testing.T) {
 		}
 	}
 }
+
+func TestSortValues(t *testing.T) {
+	v := reflect.ValueOf
+
+	a := v("a")
+	b := v("b")
+	c := v("c")
+	tests := []struct {
+		input    []reflect.Value
+		expected []reflect.Value
+	}{
+		{[]reflect.Value{v(2), v(1), v(3)},
+			[]reflect.Value{v(1), v(2), v(3)}},
+		{[]reflect.Value{v(2.), v(1.), v(3.)},
+			[]reflect.Value{v(1.), v(2.), v(3.)}},
+		{[]reflect.Value{v(false), v(true), v(false)},
+			[]reflect.Value{v(false), v(false), v(true)}},
+		{[]reflect.Value{b, a, c},
+			[]reflect.Value{a, b, c}},
+	}
+	for _, test := range tests {
+		spew.SortValues(test.input)
+		if !reflect.DeepEqual(test.input, test.expected) {
+			t.Errorf("Sort mismatch:\n %v != %v", test.input, test.expected)
+		}
+	}
+}
+
+func TestDumpSortedKeys(t *testing.T) {
+	cfg := spew.ConfigState{SortKeys: true}
+	s := cfg.Sdump(map[int]string{1: "1", 3: "3", 2: "2"})
+	expected := `(map[int]string) {
+(int) 1: (string) "1",
+(int) 2: (string) "2",
+(int) 3: (string) "3"
+}
+`
+	if s != expected {
+		t.Errorf("Sorted keys mismatch:\n  %v %v", s, expected)
+	}
+}