Implment issue 28 with FLAG_IGNORE_SLICE_ORDER

deep.go

@@ -56,10 +56,24 @@ var (
 	ErrNotHandled = errors.New("cannot compare the reflect.Kind")
 )
 
+const (
+	// FLAG_NONE is a placeholder for default Equal behavior. You don't have to
+	// pass it to Equal; if you do, it does nothing.
+	FLAG_NONE byte = iota
+
+	// FLAG_IGNORE_SLICE_ORDER causes Equal to ignore slice order so that
+	// []int{1, 2} and []int{2, 1} are equal. Only slices of primitive scalars
+	// like numbers and strings are supported. Slices of complex types,
+	// like []T where T is a struct, are undefined because Equal does not
+	// recurse into the slice value when this flag is enabled.
+	FLAG_IGNORE_SLICE_ORDER
+)
+
 type cmp struct {
 	diff        []string
 	buff        []string
 	floatFormat string
+	flag        map[byte]bool
 }
 
 var errorType = reflect.TypeOf((*error)(nil)).Elem()
@@ -74,13 +88,17 @@ var errorType = reflect.TypeOf((*error)(nil)).Elem()
 //
 // When comparing a struct, if a field has the tag `deep:"-"` then it will be
 // ignored.
-func Equal(a, b interface{}) []string {
+func Equal(a, b interface{}, flags ...interface{}) []string {
 	aVal := reflect.ValueOf(a)
 	bVal := reflect.ValueOf(b)
 	c := &cmp{
 		diff:        []string{},
 		buff:        []string{},
 		floatFormat: fmt.Sprintf("%%.%df", FloatPrecision),
+		flag:        map[byte]bool{},
+	}
+	for i := range flags {
+		c.flag[flags[i].(byte)] = true
 	}
 	if a == nil && b == nil {
 		return nil
@@ -339,29 +357,54 @@ func (c *cmp) equals(a, b reflect.Value, level int) {
 			}
 		}
 
+		// Equal if same underlying pointer and same length, this latter handles
+		//   foo := []int{1, 2, 3, 4}
+		//   a := foo[0:2] // == {1,2}
+		//   b := foo[2:4] // == {3,4}
+		// a and b are same pointer but different slices (lengths) of the underlying
+		// array, so not equal.
 		aLen := a.Len()
 		bLen := b.Len()
-
 		if a.Pointer() == b.Pointer() && aLen == bLen {
 			return
 		}
 
-		n := aLen
-		if bLen > aLen {
-			n = bLen
-		}
-		for i := 0; i < n; i++ {
-			c.push(fmt.Sprintf("slice[%d]", i))
-			if i < aLen && i < bLen {
-				c.equals(a.Index(i), b.Index(i), level+1)
-			} else if i < aLen {
-				c.saveDiff(a.Index(i), "<no value>")
-			} else {
-				c.saveDiff("<no value>", b.Index(i))
+		if c.flag[FLAG_IGNORE_SLICE_ORDER] {
+			// Compare slices by value and value count; ignore order.
+			// Value equality is impliclity established by the maps:
+			// any value v1 will hash to the same map value if it's equal
+			// to another value v2. Then equality is determiend by value
+			// count: presuming v1==v2, then the slics are equal if there
+			// are equal numbers of v1 in each slice.
+			am := map[interface{}]int{}
+			for i := 0; i < a.Len(); i++ {
+				am[a.Index(i).Interface()] += 1
 			}
-			c.pop()
-			if len(c.diff) >= MaxDiff {
-				break
+			bm := map[interface{}]int{}
+			for i := 0; i < b.Len(); i++ {
+				bm[b.Index(i).Interface()] += 1
+			}
+			c.cmpMapValueCounts(a, b, am, bm, true)  // a cmp b
+			c.cmpMapValueCounts(b, a, bm, am, false) // b cmp a
+		} else {
+			// Compare slices by order
+			n := aLen
+			if bLen > aLen {
+				n = bLen
+			}
+			for i := 0; i < n; i++ {
+				c.push(fmt.Sprintf("slice[%d]", i))
+				if i < aLen && i < bLen {
+					c.equals(a.Index(i), b.Index(i), level+1)
+				} else if i < aLen {
+					c.saveDiff(a.Index(i), "<no value>")
+				} else {
+					c.saveDiff("<no value>", b.Index(i))
+				}
+				c.pop()
+				if len(c.diff) >= MaxDiff {
+					break
+				}
 			}
 		}
 
@@ -435,6 +478,25 @@ func (c *cmp) saveDiff(aval, bval interface{}) {
 	}
 }
 
+func (c *cmp) cmpMapValueCounts(a, b reflect.Value, am, bm map[interface{}]int, a2b bool) {
+	for v := range am {
+		aCount, _ := am[v]
+		bCount, _ := bm[v]
+
+		if aCount != bCount {
+			c.push(fmt.Sprintf("(unordered) slice[]=%v: value count", v))
+			if a2b {
+				c.saveDiff(fmt.Sprintf("%d", aCount), fmt.Sprintf("%d", bCount))
+			} else {
+				c.saveDiff(fmt.Sprintf("%d", bCount), fmt.Sprintf("%d", aCount))
+			}
+			c.pop()
+		}
+		delete(am, v)
+		delete(bm, v)
+	}
+}
+
 func logError(err error) {
 	if LogErrors {
 		log.Println(err)

deep_test.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"sort"
 	"testing"
 	"time"
 	"unsafe"
@@ -1495,3 +1496,88 @@ func TestFunc(t *testing.T) {
 		t.Errorf("expected 0 diff, got %d: %s", len(diff), diff)
 	}
 }
+
+func TestSliceOrderString(t *testing.T) {
+	// https://github.com/go-test/deep/issues/28
+
+	// These are equal if we ignore order
+	a := []string{"foo", "bar"}
+	b := []string{"bar", "foo"}
+	diff := deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 0 {
+		t.Fatalf("expected 0 diff, got %d: %s", len(diff), diff)
+	}
+
+	// Equal with dupes
+	a = []string{"foo", "foo", "bar"}
+	b = []string{"bar", "foo", "foo"}
+	diff = deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 0 {
+		t.Fatalf("expected 0 diff, got %d: %s", len(diff), diff)
+	}
+
+	// NOT equal with dupes
+	a = []string{"foo", "foo", "bar"}
+	b = []string{"bar", "bar", "foo"}
+	diff = deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 2 {
+		t.Fatalf("expected 2 diff, got %d: %s", len(diff), diff)
+	}
+	m1 := "(unordered) slice[]=foo: value count: 2 != 1"
+	m2 := "(unordered) slice[]=bar: value count: 1 != 2"
+	if diff[0] != m1 && diff[0] != m2 {
+		t.Errorf("got %s, expected '%s' or '%s'", diff[0], m1, m2)
+	}
+	if diff[1] != m1 && diff[1] != m2 {
+		t.Errorf("got %s, expected '%s' or '%s'", diff[1], m1, m2)
+	}
+
+	// NOT equal with one missing
+	a = []string{"foo", "bar"}
+	b = []string{"bar", "foo", "gone"}
+	diff = deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 1 {
+		t.Fatalf("expected 2 diff, got %d: %s", len(diff), diff)
+	}
+	if diff[0] != "(unordered) slice[]=gone: value count: 0 != 1" {
+		t.Errorf("got %s, expected ''", diff[0])
+	}
+
+	// NOT equal at all
+	a = []string{"foo", "bar"}
+	b = []string{"x"}
+	diff = deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 3 {
+		t.Fatalf("expected 2 diff, got %d: %s", len(diff), diff)
+	}
+	sort.Strings(diff)
+	if diff[0] != "(unordered) slice[]=bar: value count: 1 != 0" {
+		t.Errorf("got %s, expected '(unordered) slice[]=bar: value count: 1 != 0'", diff[0])
+	}
+	if diff[1] != "(unordered) slice[]=foo: value count: 1 != 0" {
+		t.Errorf("got %s, expected '(unordered) slice[]=foo: value count: 1 != 0", diff[1])
+	}
+	if diff[2] != "(unordered) slice[]=x: value count: 0 != 1" {
+		t.Errorf("got %s, expected '(unordered) slice[]=x: value count: 0 != 1'", diff[2])
+	}
+}
+
+func TestSliceOrderStruct(t *testing.T) {
+	// https://github.com/go-test/deep/issues/28
+	// This is NOT supported but Go is so wonderful that it just happens to work.
+	// But again: not supported. So if this test starts to fail or be a problem,
+	// it can and should be removed becuase the docs say it's not supported.
+	type T struct{ i int }
+	a := []T{
+		{i: 1},
+		{i: 2},
+	}
+	b := []T{
+		{i: 2},
+		{i: 1},
+	}
+	diff := deep.Equal(a, b, deep.FLAG_IGNORE_SLICE_ORDER)
+	if len(diff) != 0 {
+		t.Fatalf("expected 0 diff, got %d: %s", len(diff), diff)
+	}
+}