mirror of
https://github.com/tailscale/tailscale.git
synced 2025-10-10 09:45:08 +00:00
types/opt: add generic Value[T any] for optional values of any types
Updates #12736 Signed-off-by: Nick Khyl <nickk@tailscale.com>
This commit is contained in:
Nick Khyl
122
types/opt/value.go
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122
types/opt/value.go
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@@ -0,0 +1,122 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package opt
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import (
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"fmt"
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"reflect"
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jsonv2 "github.com/go-json-experiment/json"
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"github.com/go-json-experiment/json/jsontext"
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)
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// Value is an optional value to be JSON-encoded.
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// With [encoding/json], a zero Value is marshaled as a JSON null.
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// With [github.com/go-json-experiment/json], a zero Value is omitted from the
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// JSON object if the Go struct field specified with omitzero.
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// The omitempty tag option should never be used with Value fields.
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type Value[T any] struct {
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value T
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set bool
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}
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// Equal reports whether the receiver and the other value are equal.
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// If the template type T in Value[T] implements an Equal method, it will be used
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// instead of the == operator for comparing values.
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type equatable[T any] interface {
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// Equal reports whether the receiver and the other values are equal.
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Equal(other T) bool
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}
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// ValueOf returns an optional Value containing the specified value.
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// It treats nil slices and maps as empty slices and maps.
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func ValueOf[T any](v T) Value[T] {
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return Value[T]{value: v, set: true}
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}
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// String implements [fmt.Stringer].
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func (o *Value[T]) String() string {
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if !o.set {
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return fmt.Sprintf("(empty[%T])", o.value)
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}
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return fmt.Sprint(o.value)
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}
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// Set assigns the specified value to the optional value o.
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func (o *Value[T]) Set(v T) {
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*o = ValueOf(v)
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}
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// Clear resets o to an empty state.
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func (o *Value[T]) Clear() {
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*o = Value[T]{}
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}
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// IsSet reports whether o has a value set.
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func (o *Value[T]) IsSet() bool {
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return o.set
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}
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// Get returns the value of o.
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// If a value hasn't been set, a zero value of T will be returned.
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func (o Value[T]) Get() T {
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return o.value
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}
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// Get returns the value and a flag indicating whether the value is set.
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func (o Value[T]) GetOk() (v T, ok bool) {
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return o.value, o.set
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}
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// Equal reports whether o is equal to v.
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// Two optional values are equal if both are empty,
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// or if both are set and the underlying values are equal.
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// If the template type T implements an Equal(T) bool method, it will be used
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// instead of the == operator for value comparison.
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// If T is not comparable, it returns false.
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func (o Value[T]) Equal(v Value[T]) bool {
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if o.set != v.set {
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return false
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}
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if !o.set {
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return true
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}
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ov := any(o.value)
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if eq, ok := ov.(equatable[T]); ok {
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return eq.Equal(v.value)
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}
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if reflect.TypeFor[T]().Comparable() {
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return ov == any(v.value)
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}
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return false
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}
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// MarshalJSONV2 implements [jsonv2.MarshalerV2].
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func (o Value[T]) MarshalJSONV2(enc *jsontext.Encoder, opts jsonv2.Options) error {
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if !o.set {
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return enc.WriteToken(jsontext.Null)
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}
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return jsonv2.MarshalEncode(enc, &o.value, opts)
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}
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// UnmarshalJSONV2 implements [jsonv2.UnmarshalerV2].
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func (o *Value[T]) UnmarshalJSONV2(dec *jsontext.Decoder, opts jsonv2.Options) error {
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if dec.PeekKind() == 'n' {
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*o = Value[T]{}
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_, err := dec.ReadToken() // read null
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return err
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}
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o.set = true
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return jsonv2.UnmarshalDecode(dec, &o.value, opts)
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}
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// MarshalJSON implements [json.Marshaler].
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func (o Value[T]) MarshalJSON() ([]byte, error) {
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return jsonv2.Marshal(o) // uses MarshalJSONV2
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}
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// UnmarshalJSON implements [json.Unmarshaler].
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func (o *Value[T]) UnmarshalJSON(b []byte) error {
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return jsonv2.Unmarshal(b, o) // uses UnmarshalJSONV2
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}
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296
types/opt/value_test.go
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296
types/opt/value_test.go
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@@ -0,0 +1,296 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package opt
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import (
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"encoding/json"
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"reflect"
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"testing"
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jsonv2 "github.com/go-json-experiment/json"
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)
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type testStruct struct {
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Int int `json:",omitempty,omitzero"`
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Str string `json:",omitempty"`
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}
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func TestValue(t *testing.T) {
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tests := []struct {
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name string
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in any
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jsonv2 bool
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want string // JSON
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wantBack any
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}{
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{
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name: "null_for_unset",
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in: struct {
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True Value[bool]
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False Value[bool]
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Unset Value[bool]
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ExplicitUnset Value[bool]
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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ExplicitUnset: Value[bool]{},
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},
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want: `{"True":true,"False":false,"Unset":null,"ExplicitUnset":null}`,
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wantBack: struct {
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True Value[bool]
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False Value[bool]
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Unset Value[bool]
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ExplicitUnset Value[bool]
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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Unset: Value[bool]{},
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ExplicitUnset: Value[bool]{},
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},
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},
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{
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name: "null_for_unset_jsonv2",
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in: struct {
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True Value[bool]
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False Value[bool]
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Unset Value[bool]
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ExplicitUnset Value[bool]
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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ExplicitUnset: Value[bool]{},
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},
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jsonv2: true,
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want: `{"True":true,"False":false,"Unset":null,"ExplicitUnset":null}`,
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wantBack: struct {
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True Value[bool]
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False Value[bool]
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Unset Value[bool]
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ExplicitUnset Value[bool]
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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Unset: Value[bool]{},
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ExplicitUnset: Value[bool]{},
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},
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},
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{
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name: "null_for_unset_omitzero",
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in: struct {
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True Value[bool] `json:",omitzero"`
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False Value[bool] `json:",omitzero"`
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Unset Value[bool] `json:",omitzero"`
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ExplicitUnset Value[bool] `json:",omitzero"`
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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ExplicitUnset: Value[bool]{},
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},
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want: `{"True":true,"False":false,"Unset":null,"ExplicitUnset":null}`,
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wantBack: struct {
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True Value[bool] `json:",omitzero"`
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False Value[bool] `json:",omitzero"`
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Unset Value[bool] `json:",omitzero"`
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ExplicitUnset Value[bool] `json:",omitzero"`
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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Unset: Value[bool]{},
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ExplicitUnset: Value[bool]{},
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},
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},
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{
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name: "null_for_unset_omitzero_jsonv2",
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in: struct {
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True Value[bool] `json:",omitzero"`
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False Value[bool] `json:",omitzero"`
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Unset Value[bool] `json:",omitzero"`
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ExplicitUnset Value[bool] `json:",omitzero"`
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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ExplicitUnset: Value[bool]{},
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},
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jsonv2: true,
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want: `{"True":true,"False":false}`,
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wantBack: struct {
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True Value[bool] `json:",omitzero"`
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False Value[bool] `json:",omitzero"`
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Unset Value[bool] `json:",omitzero"`
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ExplicitUnset Value[bool] `json:",omitzero"`
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}{
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True: ValueOf(true),
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False: ValueOf(false),
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Unset: Value[bool]{},
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ExplicitUnset: Value[bool]{},
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},
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},
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{
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name: "string",
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in: struct {
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EmptyString Value[string]
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NonEmpty Value[string]
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Unset Value[string]
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}{
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EmptyString: ValueOf(""),
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NonEmpty: ValueOf("value"),
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Unset: Value[string]{},
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},
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want: `{"EmptyString":"","NonEmpty":"value","Unset":null}`,
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wantBack: struct {
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EmptyString Value[string]
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NonEmpty Value[string]
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Unset Value[string]
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}{ValueOf(""), ValueOf("value"), Value[string]{}},
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},
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{
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name: "integer",
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in: struct {
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Zero Value[int]
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NonZero Value[int]
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Unset Value[int]
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}{
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Zero: ValueOf(0),
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NonZero: ValueOf(42),
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Unset: Value[int]{},
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},
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want: `{"Zero":0,"NonZero":42,"Unset":null}`,
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wantBack: struct {
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Zero Value[int]
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NonZero Value[int]
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Unset Value[int]
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}{ValueOf(0), ValueOf(42), Value[int]{}},
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},
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{
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name: "struct",
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in: struct {
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Zero Value[testStruct]
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NonZero Value[testStruct]
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Unset Value[testStruct]
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}{
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Zero: ValueOf(testStruct{}),
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NonZero: ValueOf(testStruct{Int: 42, Str: "String"}),
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Unset: Value[testStruct]{},
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},
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want: `{"Zero":{},"NonZero":{"Int":42,"Str":"String"},"Unset":null}`,
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wantBack: struct {
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Zero Value[testStruct]
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NonZero Value[testStruct]
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Unset Value[testStruct]
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}{ValueOf(testStruct{}), ValueOf(testStruct{Int: 42, Str: "String"}), Value[testStruct]{}},
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},
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{
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name: "struct_ptr",
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in: struct {
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Zero Value[*testStruct]
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NonZero Value[*testStruct]
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Unset Value[*testStruct]
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}{
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Zero: ValueOf(&testStruct{}),
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NonZero: ValueOf(&testStruct{Int: 42, Str: "String"}),
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Unset: Value[*testStruct]{},
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},
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want: `{"Zero":{},"NonZero":{"Int":42,"Str":"String"},"Unset":null}`,
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wantBack: struct {
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Zero Value[*testStruct]
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NonZero Value[*testStruct]
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Unset Value[*testStruct]
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}{ValueOf(&testStruct{}), ValueOf(&testStruct{Int: 42, Str: "String"}), Value[*testStruct]{}},
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},
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{
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name: "nil-slice-and-map",
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in: struct {
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Slice Value[[]int]
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Map Value[map[string]int]
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}{
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Slice: ValueOf[[]int](nil), // marshalled as []
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Map: ValueOf[map[string]int](nil), // marshalled as {}
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},
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want: `{"Slice":[],"Map":{}}`,
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wantBack: struct {
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Slice Value[[]int]
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Map Value[map[string]int]
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}{ValueOf([]int{}), ValueOf(map[string]int{})},
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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var j []byte
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var err error
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if tt.jsonv2 {
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j, err = jsonv2.Marshal(tt.in)
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} else {
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j, err = json.Marshal(tt.in)
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}
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if err != nil {
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t.Fatal(err)
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}
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if string(j) != tt.want {
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t.Errorf("wrong JSON:\n got: %s\nwant: %s\n", j, tt.want)
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}
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wantBack := tt.in
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if tt.wantBack != nil {
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wantBack = tt.wantBack
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}
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// And back again:
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newVal := reflect.New(reflect.TypeOf(tt.in))
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out := newVal.Interface()
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if tt.jsonv2 {
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err = jsonv2.Unmarshal(j, out)
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} else {
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err = json.Unmarshal(j, out)
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}
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if err != nil {
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t.Fatalf("Unmarshal %#q: %v", j, err)
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}
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got := newVal.Elem().Interface()
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if !reflect.DeepEqual(got, wantBack) {
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t.Errorf("value mismatch\n got: %+v\nwant: %+v\n", got, wantBack)
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}
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})
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}
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}
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func TestValueEqual(t *testing.T) {
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tests := []struct {
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o Value[bool]
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v Value[bool]
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want bool
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}{
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{ValueOf(true), ValueOf(true), true},
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{ValueOf(true), ValueOf(false), false},
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{ValueOf(true), Value[bool]{}, false},
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{ValueOf(false), ValueOf(false), true},
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{ValueOf(false), ValueOf(true), false},
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{ValueOf(false), Value[bool]{}, false},
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{Value[bool]{}, Value[bool]{}, true},
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{Value[bool]{}, ValueOf(true), false},
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{Value[bool]{}, ValueOf(false), false},
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}
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for _, tt := range tests {
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if got := tt.o.Equal(tt.v); got != tt.want {
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t.Errorf("(%v).Equals(%v) = %v; want %v", tt.o, tt.v, got, tt.want)
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}
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}
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}
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func TestIncomparableValueEqual(t *testing.T) {
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tests := []struct {
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o Value[[]bool]
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v Value[[]bool]
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want bool
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}{
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{ValueOf([]bool{}), ValueOf([]bool{}), false},
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{ValueOf([]bool{true}), ValueOf([]bool{true}), false},
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{Value[[]bool]{}, ValueOf([]bool{}), false},
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{ValueOf([]bool{}), Value[[]bool]{}, false},
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{Value[[]bool]{}, Value[[]bool]{}, true},
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}
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for _, tt := range tests {
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if got := tt.o.Equal(tt.v); got != tt.want {
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t.Errorf("(%v).Equals(%v) = %v; want %v", tt.o, tt.v, got, tt.want)
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}
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}
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}
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Reference in New Issue
Block a user