Merge pull request #3220 from lavalamp/deepEqual

Add *useful* DeepEqual

pkg/conversion/converter.go

@@ -395,7 +395,9 @@ func (c *Converter) defaultConvert(sv, dv reflect.Value, scope *scope) error {
 	dt, st := dv.Type(), sv.Type()
 
 	if !scope.flags.IsSet(AllowDifferentFieldTypeNames) && c.NameFunc(dt) != c.NameFunc(st) {
-		return scope.error("type names don't match (%v, %v)", c.NameFunc(st), c.NameFunc(dt))
+		return scope.error(
+			"type names don't match (%v, %v), and no conversion 'func (%v, %v) error' registered.",
+			c.NameFunc(st), c.NameFunc(dt), st, dt)
 	}
 
 	// This should handle all simple types.

pkg/conversion/deep_equal.go

@@ -0,0 +1,235 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package conversion
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// Equalities is a map from type to a function comparing two values of
+// that type.
+type Equalities map[reflect.Type]reflect.Value
+
+// For convenience, panics on errrors
+func EqualitiesOrDie(funcs ...interface{}) Equalities {
+	e := Equalities{}
+	if err := e.AddFuncs(funcs...); err != nil {
+		panic(err)
+	}
+	return e
+}
+
+// AddFuncs is a shortcut for multiple calls to AddFunc.
+func (e Equalities) AddFuncs(funcs ...interface{}) error {
+	for _, f := range funcs {
+		if err := e.AddFunc(f); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// AddFunc uses func as an equality function: it must take
+// two parameters of the same type, and return a boolean.
+func (e Equalities) AddFunc(eqFunc interface{}) error {
+	fv := reflect.ValueOf(eqFunc)
+	ft := fv.Type()
+	if ft.Kind() != reflect.Func {
+		return fmt.Errorf("expected func, got: %v", ft)
+	}
+	if ft.NumIn() != 2 {
+		return fmt.Errorf("expected three 'in' params, got: %v", ft)
+	}
+	if ft.NumOut() != 1 {
+		return fmt.Errorf("expected one 'out' param, got: %v", ft)
+	}
+	if ft.In(0) != ft.In(1) {
+		return fmt.Errorf("expected arg 1 and 2 to have same type, but got %v", ft)
+	}
+	var forReturnType bool
+	boolType := reflect.TypeOf(forReturnType)
+	if ft.Out(0) != boolType {
+		return fmt.Errorf("expected bool return, got: %v", ft)
+	}
+	e[ft.In(0)] = fv
+	return nil
+}
+
+// Equal return true if a matching equality function thinks a == b;
+// if there is no matching equality function, it calls the standard
+// go == operator.
+func (e Equalities) Equal(a, b interface{}) bool {
+	av, bv := reflect.ValueOf(a), reflect.ValueOf(a)
+	if !av.IsValid() || !av.IsValid() {
+		return av.IsValid() == av.IsValid()
+	}
+	if av.Type() != av.Type() {
+		return false
+	}
+	if fv, ok := e[av.Type()]; ok {
+		return fv.Call([]reflect.Value{av, bv})[0].Bool()
+	}
+	return av.Interface() == bv.Interface()
+}
+
+// Below here is forked from go's reflect/deepequal.go
+
+// During deepValueEqual, must keep track of checks that are
+// in progress.  The comparison algorithm assumes that all
+// checks in progress are true when it reencounters them.
+// Visited comparisons are stored in a map indexed by visit.
+type visit struct {
+	a1  uintptr
+	a2  uintptr
+	typ reflect.Type
+}
+
+// Tests for deep equality using reflected types. The map argument tracks
+// comparisons that have already been seen, which allows short circuiting on
+// recursive types.
+func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool, depth int) bool {
+	if !v1.IsValid() || !v2.IsValid() {
+		return v1.IsValid() == v2.IsValid()
+	}
+	if v1.Type() != v2.Type() {
+		return false
+	}
+	if fv, ok := e[v1.Type()]; ok {
+		return fv.Call([]reflect.Value{v1, v2})[0].Bool()
+	}
+
+	hard := func(k reflect.Kind) bool {
+		switch k {
+		case reflect.Array, reflect.Map, reflect.Slice, reflect.Struct:
+			return true
+		}
+		return false
+	}
+
+	if v1.CanAddr() && v2.CanAddr() && hard(v1.Kind()) {
+		addr1 := v1.UnsafeAddr()
+		addr2 := v2.UnsafeAddr()
+		if addr1 > addr2 {
+			// Canonicalize order to reduce number of entries in visited.
+			addr1, addr2 = addr2, addr1
+		}
+
+		// Short circuit if references are identical ...
+		if addr1 == addr2 {
+			return true
+		}
+
+		// ... or already seen
+		typ := v1.Type()
+		v := visit{addr1, addr2, typ}
+		if visited[v] {
+			return true
+		}
+
+		// Remember for later.
+		visited[v] = true
+	}
+
+	switch v1.Kind() {
+	case reflect.Array:
+		for i := 0; i < v1.Len(); i++ {
+			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case reflect.Slice:
+		if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
+			return false
+		}
+		if v1.IsNil() || v1.Len() == 0 {
+			return true
+		}
+		if v1.Pointer() == v2.Pointer() {
+			return true
+		}
+		for i := 0; i < v1.Len(); i++ {
+			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case reflect.Interface:
+		if v1.IsNil() || v2.IsNil() {
+			return v1.IsNil() == v2.IsNil()
+		}
+		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
+	case reflect.Ptr:
+		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
+	case reflect.Struct:
+		for i, n := 0, v1.NumField(); i < n; i++ {
+			if !e.deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case reflect.Map:
+		if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
+			return false
+		}
+		if v1.IsNil() || v1.Len() == 0 {
+			return true
+		}
+		if v1.Pointer() == v2.Pointer() {
+			return true
+		}
+		for _, k := range v1.MapKeys() {
+			if !e.deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
+				return false
+			}
+		}
+		return true
+	case reflect.Func:
+		if v1.IsNil() && v2.IsNil() {
+			return true
+		}
+		// Can't do better than this:
+		return false
+	default:
+		// Normal equality suffices
+		if v1.CanInterface() && v2.CanInterface() {
+			return v1.Interface() == v2.Interface()
+		}
+		return v1.CanInterface() == v2.CanInterface()
+	}
+}
+
+// DeepEqual is like reflect.DeepEqual, but focused on semantic equality
+// instead of memory equality.
+//
+// It will use e's equality functions if it finds types that match.
+//
+// An empty slice *is* equal to a nil slice for our purposes; same for maps.
+//
+// Unexported field members are not compared.
+func (e Equalities) DeepEqual(a1, a2 interface{}) bool {
+	if a1 == nil || a2 == nil {
+		return a1 == a2
+	}
+	v1 := reflect.ValueOf(a1)
+	v2 := reflect.ValueOf(a2)
+	if v1.Type() != v2.Type() {
+		return false
+	}
+	return e.deepValueEqual(v1, v2, make(map[visit]bool), 0)
+}

pkg/conversion/deep_equal_test.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package conversion
+
+import (
+	"testing"
+)
+
+func TestEqualities(t *testing.T) {
+	e := Equalities{}
+	err := e.AddFuncs(
+		func(a, b int) bool {
+			return a+1 == b
+		},
+	)
+	if err != nil {
+		t.Fatalf("Unexpected: %v", err)
+	}
+
+	table := []struct {
+		a, b  interface{}
+		equal bool
+	}{
+		{1, 2, true},
+		{2, 1, false},
+		{"foo", "foo", true},
+		{map[string]int{"foo": 1}, map[string]int{"foo": 2}, true},
+		{map[string]int{}, map[string]int(nil), true},
+		{[]int{}, []int(nil), true},
+	}
+
+	for _, item := range table {
+		if e, a := item.equal, e.DeepEqual(item.a, item.b); e != a {
+			t.Errorf("Expected (%+v == %+v) == %v, but got %v", item.a, item.b, e, a)
+		}
+	}
+}