implement equality of struct (#1)

deepequal.go

@@ -0,0 +1,149 @@
+// Some code is written referencing following codes:
+// - deepequal.go in "reflect" package authored by Go Authors
+// - deepequal.go in "github.com/weaveworks/scope/test/reflect" package authored by Weaveworks Ltd
+
+package teq
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// 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  unsafe.Pointer
+	a2  unsafe.Pointer
+	typ reflect.Type
+}
+
+const maxDepth = 1_000
+
+func (teq Teq) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool, depth int) bool {
+	if depth > maxDepth {
+		panic("maximum depth exceeded")
+	}
+	if !v1.IsValid() || !v2.IsValid() {
+		return v1.IsValid() == v2.IsValid()
+	}
+	if v1.Type() != v2.Type() {
+		return false
+	}
+
+	if hard(v1.Kind()) {
+		if v1.CanAddr() && v2.CanAddr() {
+			addr1 := v1.Addr().UnsafePointer()
+			addr2 := v2.Addr().UnsafePointer()
+
+			// Short circuit
+			if uintptr(addr1) == uintptr(addr2) {
+				return true
+			}
+			if uintptr(addr1) > uintptr(addr2) {
+				// Canonicalize order to reduce number of entries in visited.
+				addr1, addr2 = addr2, addr1
+			}
+
+			// Short circuit if references are already seen.
+			typ := v1.Type()
+			v := visit{addr1, addr2, typ}
+			if visited[v] {
+				return true
+			}
+
+			// Remember for later.
+			visited[v] = true
+		}
+	}
+
+	eqFn, ok := eqs[v1.Kind()]
+	if !ok {
+		panic("not implemented")
+	}
+	var n next = func(v1, v2 reflect.Value) bool {
+		return teq.deepValueEqual(v1, v2, visited, depth+1)
+	}
+	return eqFn(teq, v1, v2, n)
+}
+
+type next func(v1, v2 reflect.Value) bool
+
+var eqs = map[reflect.Kind]func(teq Teq, v1, v2 reflect.Value, nx next) bool{
+	reflect.Array:      arrayEq,
+	reflect.Slice:      todo,
+	reflect.Interface:  interfaceEq,
+	reflect.Pointer:    pointerEq,
+	reflect.Struct:     structEq,
+	reflect.Map:        todo,
+	reflect.Func:       todo,
+	reflect.Int:        intEq,
+	reflect.Int8:       intEq,
+	reflect.Int16:      intEq,
+	reflect.Int32:      intEq,
+	reflect.Int64:      intEq,
+	reflect.Uint:       uintEq,
+	reflect.Uint8:      uintEq,
+	reflect.Uint16:     uintEq,
+	reflect.Uint32:     uintEq,
+	reflect.Uint64:     uintEq,
+	reflect.Uintptr:    uintEq,
+	reflect.String:     stringEq,
+	reflect.Bool:       boolEq,
+	reflect.Float32:    floatEq,
+	reflect.Float64:    floatEq,
+	reflect.Complex64:  complexEq,
+	reflect.Complex128: complexEq,
+}
+
+func hard(k reflect.Kind) bool {
+	switch k {
+	case reflect.Array, reflect.Slice, reflect.Map, reflect.Struct:
+		return true
+	}
+	return false
+}
+
+func todo(teq Teq, v1, v2 reflect.Value, nx next) bool {
+	panic("not implemented")
+}
+
+func arrayEq(teq Teq, v1, v2 reflect.Value, nx next) bool {
+	for i := 0; i < v1.Len(); i++ {
+		if !nx(v1.Index(i), v2.Index(i)) {
+			return false
+		}
+	}
+	return true
+}
+
+func interfaceEq(teq Teq, v1, v2 reflect.Value, nx next) bool {
+	if v1.IsNil() || v2.IsNil() {
+		return v1.IsNil() == v2.IsNil()
+	}
+	return nx(v1.Elem(), v2.Elem())
+}
+
+func pointerEq(teq Teq, v1, v2 reflect.Value, nx next) bool {
+	if v1.UnsafePointer() == v2.UnsafePointer() {
+		return true
+	}
+	return nx(v1.Elem(), v2.Elem())
+}
+
+func structEq(teq Teq, v1, v2 reflect.Value, nx next) bool {
+	for i, n := 0, v1.NumField(); i < n; i++ {
+		if !nx(v1.Field(i), v2.Field(i)) {
+			return false
+		}
+	}
+	return true
+}
+
+func intEq(_ Teq, v1, v2 reflect.Value, _ next) bool     { return v1.Int() == v2.Int() }
+func uintEq(_ Teq, v1, v2 reflect.Value, _ next) bool    { return v1.Uint() == v2.Uint() }
+func stringEq(_ Teq, v1, v2 reflect.Value, _ next) bool  { return v1.String() == v2.String() }
+func boolEq(_ Teq, v1, v2 reflect.Value, _ next) bool    { return v1.Bool() == v2.Bool() }
+func floatEq(_ Teq, v1, v2 reflect.Value, _ next) bool   { return v1.Float() == v2.Float() }
+func complexEq(_ Teq, v1, v2 reflect.Value, _ next) bool { return v1.Complex() == v2.Complex() }

teq.go

@@ -0,0 +1,33 @@
+package teq
+
+import (
+	"reflect"
+)
+
+type Teq struct{}
+
+func (teq Teq) Equal(t TestingT, expected, actual any) bool {
+	t.Helper()
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("panic: %v", r)
+		}
+	}()
+	ok := teq.equal(expected, actual)
+	if !ok {
+		t.Errorf("expected %v, got %v", expected, actual)
+	}
+	return ok
+}
+
+func (teq Teq) equal(x, y any) bool {
+	if x == nil || y == nil {
+		return x == y
+	}
+	v1 := reflect.ValueOf(x)
+	v2 := reflect.ValueOf(y)
+	if v1.Type() != v2.Type() {
+		return false
+	}
+	return teq.deepValueEqual(v1, v2, make(map[visit]bool), 0)
+}

teq_test.go

@@ -0,0 +1,138 @@
+package teq_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/seiyab/teq"
+)
+
+type test struct {
+	a             any
+	b             any
+	expected      []string
+	pendingFormat bool // for development. we don't have stable format yet.
+}
+
+type group struct {
+	name  string
+	tests []test
+}
+
+func TestEqual(t *testing.T) {
+	assert := teq.Teq{}
+
+	groups := []group{
+		{"primitives", primitives()},
+		{"structs", structs()},
+		{"recursions", recursions()},
+	}
+
+	for _, group := range groups {
+		t.Run(group.name, func(t *testing.T) {
+			for _, test := range group.tests {
+				name := fmt.Sprintf("%T(%v) == %T(%v)", test.a, test.a, test.b, test.b)
+				t.Run(name, func(t *testing.T) {
+					mt := &mockT{}
+					assert.Equal(mt, test.a, test.b)
+					if len(mt.errors) != len(test.expected) {
+						if len(mt.errors) > len(test.expected) {
+							for _, e := range mt.errors {
+								t.Logf("got %q", e)
+							}
+						}
+						t.Fatalf("expected %d errors, got %d", len(test.expected), len(mt.errors))
+					}
+					if test.pendingFormat {
+						return
+					}
+					for i, e := range test.expected {
+						if mt.errors[i] != e {
+							t.Errorf("expected %q, got %q at i = %d", e, mt.errors[i], i)
+						}
+					}
+				})
+			}
+		})
+	}
+}
+
+func primitives() []test {
+	return []test{
+		{1, 1, nil, false},
+		{1, 2, []string{"expected 1, got 2"}, false},
+		{uint8(1), uint8(1), nil, false},
+		{uint8(1), uint8(2), []string{"expected 1, got 2"}, false},
+		{1.5, 1.5, nil, false},
+		{1.5, 2.5, []string{"expected 1.5, got 2.5"}, false},
+		{"a", "a", nil, false},
+		{"a", "b", []string{"expected a, got b"}, false},
+
+		{"a", 1, []string{"expected a, got 1"}, false},
+	}
+}
+
+func structs() []test {
+	type s struct {
+		i int
+	}
+	type anotherS struct {
+		i int
+	}
+
+	type withPointer struct {
+		i *int
+	}
+
+	return []test{
+		{s{1}, s{1}, nil, false},
+		{s{1}, s{2}, []string{"expected {1}, got {2}"}, false},
+		{s{1}, anotherS{1}, []string{"expected {1}, got {1}"}, false},
+
+		{withPointer{ref(1)}, withPointer{ref(1)}, nil, false},
+		{withPointer{ref(1)}, withPointer{ref(2)}, []string{"expected {1}, got {2}"}, true},
+	}
+}
+
+func recursions() []test {
+	type privateRecursiveStruct struct {
+		i int
+		r *privateRecursiveStruct
+	}
+	r1_1 := privateRecursiveStruct{1, nil}
+	r1_1.r = &r1_1
+	r1_2 := privateRecursiveStruct{1, nil}
+	r1_2.r = &r1_2
+	r1_3 := privateRecursiveStruct{2, nil}
+	r1_3.r = &r1_3
+	r1_4 := privateRecursiveStruct{4, nil}
+	r1_5 := privateRecursiveStruct{4, nil}
+	r1_4.r = &r1_5
+	r1_5.r = &r1_4
+	r1_6 := privateRecursiveStruct{4, nil}
+	r1_6.r = &r1_6
+
+	type PublicRecursiveStruct struct {
+		I int
+		R *PublicRecursiveStruct
+	}
+	r2_1 := PublicRecursiveStruct{1, nil}
+	r2_1.R = &r2_1
+	r2_2 := PublicRecursiveStruct{1, nil}
+	r2_2.R = &r2_2
+
+	return []test{
+		{r1_1, r1_1, nil, false},
+		{r1_1, r1_2, nil, false},
+		{r1_1, r1_3, []string{"expected {1, <cyclic>}, got {2, <cyclic>}"}, true},
+		{r1_4, r1_5, nil, false},
+		{r1_4, r1_6, nil, false},
+
+		{r2_1, r2_1, nil, false},
+		{r2_1, r2_2, nil, false},
+	}
+}
+
+func ref[T any](v T) *T {
+	return &v
+}

testingt.go

@@ -3,6 +3,7 @@ package teq
 import "testing"
 
 type TestingT interface {
+	Helper()
 	Errorf(format string, args ...interface{})
 }