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zeevdrzeevdr
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feat(configwatcher): add NewGroup/Fill for struct-based field watching
Closes #18
1 parent 86cfde6 commit 5e0bd5f

2 files changed

Lines changed: 228 additions & 0 deletions

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‎sdk/configwatcher/fieldgroups.go‎

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package configwatcher
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import (
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"fmt"
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"reflect"
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"time"
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)
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// Group registers a set of watched fields mapped from a struct's `decree` tags.
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// Use [Watcher.NewGroup] to create one.
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type Group struct {
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getters []func(rv reflect.Value) // one per tagged field
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typ reflect.Type // struct type for validation
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}
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// NewGroup registers all `decree`-tagged fields in the struct pointed to by s
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// with the watcher and returns a Group. The struct pointer must remain valid
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// for the lifetime of the watcher.
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//
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// Example:
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//
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// type AppConfig struct {
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// Name string `decree:"app.name"`
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// Debug bool `decree:"app.debug"`
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// }
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// g, err := w.NewGroup(ctx, &AppConfig{})
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func (w *Watcher) NewGroup(s any) (*Group, error) {
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rv := reflect.ValueOf(s)
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if rv.Kind() != reflect.Ptr || rv.IsNil() || rv.Elem().Kind() != reflect.Struct {
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return nil, fmt.Errorf("configwatcher: NewGroup: s must be a non-nil pointer to a struct, got %T", s)
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}
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rv = rv.Elem()
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rt := rv.Type()
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g := &Group{typ: rt}
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for i := range rv.NumField() {
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field := rt.Field(i)
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tag := field.Tag.Get("decree")
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if tag == "" || tag == "-" {
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continue
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}
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fv := rv.Field(i)
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if !fv.CanSet() {
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continue
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}
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getter, err := registerGroupField(w, tag, fv)
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if err != nil {
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return nil, fmt.Errorf("configwatcher: NewGroup: field %s (decree:%q): %w", field.Name, tag, err)
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}
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idx := i
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g.getters = append(g.getters, func(target reflect.Value) {
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getter(target.Field(idx))
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})
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}
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return g, nil
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}
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// Fill populates the struct pointed to by s with the current values of all
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// watched fields. s must be the same type that was passed to NewGroup.
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func (g *Group) Fill(s any) error {
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rv := reflect.ValueOf(s)
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if rv.Kind() != reflect.Ptr || rv.IsNil() || rv.Elem().Kind() != reflect.Struct {
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return fmt.Errorf("configwatcher: Group.Fill: s must be a non-nil pointer to a struct")
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}
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rv = rv.Elem()
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if rv.Type() != g.typ {
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return fmt.Errorf("configwatcher: Group.Fill: type mismatch: got %s, want %s", rv.Type(), g.typ)
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}
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for _, get := range g.getters {
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get(rv)
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}
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return nil
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}
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var durType = reflect.TypeOf(time.Duration(0))
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func registerGroupField(w *Watcher, path string, fv reflect.Value) (func(dst reflect.Value), error) {
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switch {
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case fv.Type() == durType:
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val, err := w.Duration(path, 0)
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if err != nil {
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return nil, err
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}
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return func(dst reflect.Value) { dst.SetInt(int64(val.Get())) }, nil
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case fv.Kind() == reflect.String:
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val, err := w.String(path, "")
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if err != nil {
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return nil, err
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}
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return func(dst reflect.Value) { dst.SetString(val.Get()) }, nil
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case fv.Kind() == reflect.Bool:
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val, err := w.Bool(path, false)
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if err != nil {
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return nil, err
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}
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return func(dst reflect.Value) { dst.SetBool(val.Get()) }, nil
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case fv.Kind() >= reflect.Int && fv.Kind() <= reflect.Int64:
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val, err := w.Int(path, 0)
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if err != nil {
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return nil, err
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}
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return func(dst reflect.Value) { dst.SetInt(val.Get()) }, nil
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case fv.Kind() == reflect.Float64 || fv.Kind() == reflect.Float32:
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val, err := w.Float(path, 0)
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if err != nil {
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return nil, err
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}
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return func(dst reflect.Value) { dst.SetFloat(val.Get()) }, nil
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default:
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return nil, fmt.Errorf("unsupported field type %s", fv.Type())
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}
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}

‎sdk/configwatcher/fieldgroups_test.go‎

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package configwatcher
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import (
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"context"
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"testing"
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"time"
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"github.com/opendecree/decree/sdk/configclient"
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)
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func TestNewGroup_FillAllTypes(t *testing.T) {
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tr := &mockTransport{
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getConfigFn: func(_ context.Context, _ *configclient.GetConfigRequest) (*configclient.GetConfigResponse, error) {
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return &configclient.GetConfigResponse{
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Values: []configclient.ConfigValue{
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{FieldPath: "app.name", Value: configclient.StringVal("myapp")},
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{FieldPath: "app.debug", Value: configclient.BoolVal(true)},
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{FieldPath: "app.count", Value: configclient.IntVal(42)},
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{FieldPath: "app.rate", Value: configclient.FloatVal(1.5)},
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{FieldPath: "app.timeout", Value: configclient.DurationVal(5 * time.Second)},
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},
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}, nil
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},
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subscribeFn: func(ctx context.Context, _ *configclient.SubscribeRequest) (configclient.Subscription, error) {
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return newMockSubscription(ctx), nil
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},
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}
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type Config struct {
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Name string `decree:"app.name"`
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Debug bool `decree:"app.debug"`
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Count int64 `decree:"app.count"`
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Rate float64 `decree:"app.rate"`
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Timeout time.Duration `decree:"app.timeout"`
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Ignored string
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Skipped string `decree:"-"`
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}
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w := New(tr, "t1")
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g, err := w.NewGroup(&Config{})
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if err != nil {
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t.Fatalf("NewGroup: %v", err)
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}
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if err := w.Start(context.Background()); err != nil {
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t.Fatalf("Start: %v", err)
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}
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defer w.Close()
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var cfg Config
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if err := g.Fill(&cfg); err != nil {
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t.Fatalf("Fill: %v", err)
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}
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if cfg.Name != "myapp" {
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t.Errorf("Name = %q, want %q", cfg.Name, "myapp")
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}
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if !cfg.Debug {
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t.Error("Debug = false, want true")
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}
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if cfg.Count != 42 {
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t.Errorf("Count = %d, want 42", cfg.Count)
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}
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if cfg.Rate != 1.5 {
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t.Errorf("Rate = %f, want 1.5", cfg.Rate)
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}
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if cfg.Timeout != 5*time.Second {
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t.Errorf("Timeout = %v, want 5s", cfg.Timeout)
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}
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}
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func TestNewGroup_NonPointerError(t *testing.T) {
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tr := &mockTransport{
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getConfigFn: func(_ context.Context, _ *configclient.GetConfigRequest) (*configclient.GetConfigResponse, error) {
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return &configclient.GetConfigResponse{}, nil
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},
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subscribeFn: func(ctx context.Context, _ *configclient.SubscribeRequest) (configclient.Subscription, error) {
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return newMockSubscription(ctx), nil
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},
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}
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w := New(tr, "t1")
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type S struct{}
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_, err := w.NewGroup(S{})
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if err == nil {
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t.Error("expected error for non-pointer, got nil")
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}
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}
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func TestGroup_Fill_TypeMismatch(t *testing.T) {
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tr := &mockTransport{
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getConfigFn: func(_ context.Context, _ *configclient.GetConfigRequest) (*configclient.GetConfigResponse, error) {
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return &configclient.GetConfigResponse{}, nil
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},
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subscribeFn: func(ctx context.Context, _ *configclient.SubscribeRequest) (configclient.Subscription, error) {
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return newMockSubscription(ctx), nil
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},
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}
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w := New(tr, "t1")
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type A struct{ X string `decree:"x"` }
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type B struct{ X string `decree:"x"` }
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g, err := w.NewGroup(&A{})
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if err != nil {
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t.Fatalf("NewGroup: %v", err)
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}
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var b B
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if err := g.Fill(&b); err == nil {
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t.Error("expected type mismatch error, got nil")
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}
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}

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