cmd/viewer, types/views: implement support for json/v2 (#16852)

This adds support for having every viewer type implement
jsonv2.MarshalerTo and jsonv2.UnmarshalerFrom.

This provides a significant boost in performance
as the json package no longer needs to validate
the entirety of the JSON value outputted by MarshalJSON,
nor does it need to identify the boundaries of a JSON value
in order to call UnmarshalJSON.

For deeply nested and recursive MarshalJSON or UnmarshalJSON calls,
this can improve runtime from O(N²) to O(N).

This still references "github.com/go-json-experiment/json"
instead of the experimental "encoding/json/v2" package
now available in Go 1.25 under goexperiment.jsonv2
so that code still builds without the experiment tag.
Of note, the "github.com/go-json-experiment/json" package
aliases the standard library under the right build conditions.

Updates tailscale/corp#791

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

cmd/viewer/tests/tests_view.go

@@ -6,10 +6,12 @@
 package tests
 
 import (
-	"encoding/json"
+	jsonv1 "encoding/json"
 	"errors"
 	"net/netip"
 
+	jsonv2 "github.com/go-json-experiment/json"
+	"github.com/go-json-experiment/json/jsontext"
 	"golang.org/x/exp/constraints"
 	"tailscale.com/types/views"
 )
@@ -44,8 +46,17 @@ func (v StructWithPtrsView) AsStruct() *StructWithPtrs {
 	return v.ж.Clone()
 }
 
-func (v StructWithPtrsView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithPtrsView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithPtrsView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithPtrsView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -54,7 +65,20 @@ func (v *StructWithPtrsView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithPtrs
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithPtrsView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithPtrs
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -108,8 +132,17 @@ func (v StructWithoutPtrsView) AsStruct() *StructWithoutPtrs {
 	return v.ж.Clone()
 }
 
-func (v StructWithoutPtrsView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithoutPtrsView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithoutPtrsView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithoutPtrsView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -118,7 +151,20 @@ func (v *StructWithoutPtrsView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithoutPtrs
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithoutPtrsView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithoutPtrs
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -162,8 +208,17 @@ func (v MapView) AsStruct() *Map {
 	return v.ж.Clone()
 }
 
-func (v MapView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v MapView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v MapView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *MapView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -172,7 +227,20 @@ func (v *MapView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x Map
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *MapView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x Map
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -268,8 +336,17 @@ func (v StructWithSlicesView) AsStruct() *StructWithSlices {
 	return v.ж.Clone()
 }
 
-func (v StructWithSlicesView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithSlicesView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithSlicesView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithSlicesView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -278,7 +355,20 @@ func (v *StructWithSlicesView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithSlices
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithSlicesView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithSlices
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -342,8 +432,17 @@ func (v StructWithEmbeddedView) AsStruct() *StructWithEmbedded {
 	return v.ж.Clone()
 }
 
-func (v StructWithEmbeddedView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithEmbeddedView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithEmbeddedView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithEmbeddedView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -352,7 +451,20 @@ func (v *StructWithEmbeddedView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithEmbedded
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithEmbeddedView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithEmbedded
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -398,8 +510,17 @@ func (v GenericIntStructView[T]) AsStruct() *GenericIntStruct[T] {
 	return v.ж.Clone()
 }
 
-func (v GenericIntStructView[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v GenericIntStructView[T]) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v GenericIntStructView[T]) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *GenericIntStructView[T]) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -408,7 +529,20 @@ func (v *GenericIntStructView[T]) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x GenericIntStruct[T]
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *GenericIntStructView[T]) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x GenericIntStruct[T]
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -470,8 +604,17 @@ func (v GenericNoPtrsStructView[T]) AsStruct() *GenericNoPtrsStruct[T] {
 	return v.ж.Clone()
 }
 
-func (v GenericNoPtrsStructView[T]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v GenericNoPtrsStructView[T]) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v GenericNoPtrsStructView[T]) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *GenericNoPtrsStructView[T]) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -480,7 +623,20 @@ func (v *GenericNoPtrsStructView[T]) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x GenericNoPtrsStruct[T]
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *GenericNoPtrsStructView[T]) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x GenericNoPtrsStruct[T]
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -542,8 +698,17 @@ func (v GenericCloneableStructView[T, V]) AsStruct() *GenericCloneableStruct[T,
 	return v.ж.Clone()
 }
 
-func (v GenericCloneableStructView[T, V]) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v GenericCloneableStructView[T, V]) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v GenericCloneableStructView[T, V]) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *GenericCloneableStructView[T, V]) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -552,7 +717,20 @@ func (v *GenericCloneableStructView[T, V]) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x GenericCloneableStruct[T, V]
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *GenericCloneableStructView[T, V]) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x GenericCloneableStruct[T, V]
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -617,8 +795,17 @@ func (v StructWithContainersView) AsStruct() *StructWithContainers {
 	return v.ж.Clone()
 }
 
-func (v StructWithContainersView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithContainersView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithContainersView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithContainersView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -627,7 +814,20 @@ func (v *StructWithContainersView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithContainers
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithContainersView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithContainers
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -689,8 +889,17 @@ func (v StructWithTypeAliasFieldsView) AsStruct() *StructWithTypeAliasFields {
 	return v.ж.Clone()
 }
 
-func (v StructWithTypeAliasFieldsView) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v StructWithTypeAliasFieldsView) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v StructWithTypeAliasFieldsView) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *StructWithTypeAliasFieldsView) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -699,7 +908,20 @@ func (v *StructWithTypeAliasFieldsView) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x StructWithTypeAliasFields
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *StructWithTypeAliasFieldsView) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x StructWithTypeAliasFields
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x
@@ -787,10 +1009,17 @@ func (v GenericTypeAliasStructView[T, T2, V2]) AsStruct() *GenericTypeAliasStruc
 	return v.ж.Clone()
 }
 
+// MarshalJSON implements [jsonv1.Marshaler].
 func (v GenericTypeAliasStructView[T, T2, V2]) MarshalJSON() ([]byte, error) {
-	return json.Marshal(v.ж)
+	return jsonv1.Marshal(v.ж)
 }
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v GenericTypeAliasStructView[T, T2, V2]) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *GenericTypeAliasStructView[T, T2, V2]) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -799,7 +1028,20 @@ func (v *GenericTypeAliasStructView[T, T2, V2]) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x GenericTypeAliasStruct[T, T2, V2]
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
+		return err
+	}
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *GenericTypeAliasStructView[T, T2, V2]) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x GenericTypeAliasStruct[T, T2, V2]
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
 		return err
 	}
 	v.ж = &x

cmd/viewer/viewer.go

@@ -49,8 +49,17 @@ func (v {{.ViewName}}{{.TypeParamNames}}) AsStruct() *{{.StructName}}{{.TypePara
 	return v.ж.Clone()
 }
 
-func (v {{.ViewName}}{{.TypeParamNames}}) MarshalJSON() ([]byte, error) { return json.Marshal(v.ж) }
+// MarshalJSON implements [jsonv1.Marshaler].
+func (v {{.ViewName}}{{.TypeParamNames}}) MarshalJSON() ([]byte, error) {
+	return jsonv1.Marshal(v.ж)
+}
 
+// MarshalJSONTo implements [jsonv2.MarshalerTo].
+func (v {{.ViewName}}{{.TypeParamNames}}) MarshalJSONTo(enc *jsontext.Encoder) error {
+	return jsonv2.MarshalEncode(enc, v.ж)
+}
+
+// UnmarshalJSON implements [jsonv1.Unmarshaler].
 func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSON(b []byte) error {
 	if v.ж != nil {
 		return errors.New("already initialized")
@@ -59,10 +68,23 @@ func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSON(b []byte) error {
 		return nil
 	}
 	var x {{.StructName}}{{.TypeParamNames}}
-	if err := json.Unmarshal(b, &x); err != nil {
+	if err := jsonv1.Unmarshal(b, &x); err != nil {
 		return err
 	}
-	v.ж=&x
+	v.ж = &x
+	return nil
+}
+
+// UnmarshalJSONFrom implements [jsonv2.UnmarshalerFrom].
+func (v *{{.ViewName}}{{.TypeParamNames}}) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	if v.ж != nil {
+		return errors.New("already initialized")
+	}
+	var x {{.StructName}}{{.TypeParamNames}}
+	if err := jsonv2.UnmarshalDecode(dec, &x); err != nil {
+		return err
+	}
+	v.ж = &x
 	return nil
 }
 
@@ -125,8 +147,10 @@ func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, _ *
 	if !ok || codegen.IsViewType(t) {
 		return
 	}
-	it.Import("encoding/json")
-	it.Import("errors")
+	it.Import("jsonv1", "encoding/json")
+	it.Import("jsonv2", "github.com/go-json-experiment/json")
+	it.Import("", "github.com/go-json-experiment/json/jsontext")
+	it.Import("", "errors")
 
 	args := struct {
 		StructName     string
@@ -182,11 +206,11 @@ func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, _ *
 			switch elem.String() {
 			case "byte":
 				args.FieldType = it.QualifiedName(fieldType)
-				it.Import("tailscale.com/types/views")
+				it.Import("", "tailscale.com/types/views")
 				writeTemplate("byteSliceField")
 			default:
 				args.FieldType = it.QualifiedName(elem)
-				it.Import("tailscale.com/types/views")
+				it.Import("", "tailscale.com/types/views")
 				shallow, deep, base := requiresCloning(elem)
 				if deep {
 					switch elem.Underlying().(type) {
@@ -252,7 +276,7 @@ func genView(buf *bytes.Buffer, it *codegen.ImportTracker, typ *types.Named, _ *
 				writeTemplate("unsupportedField")
 				continue
 			}
-			it.Import("tailscale.com/types/views")
+			it.Import("", "tailscale.com/types/views")
 			args.MapKeyType = it.QualifiedName(key)
 			mElem := m.Elem()
 			var template string

cmd/viewer/viewer_test.go

@@ -20,19 +20,19 @@ func TestViewerImports(t *testing.T) {
 		name        string
 		content     string
 		typeNames   []string
-		wantImports []string
+		wantImports [][2]string
 	}{
 		{
 			name:        "Map",
 			content:     `type Test struct { Map map[string]int }`,
 			typeNames:   []string{"Test"},
-			wantImports: []string{"tailscale.com/types/views"},
+			wantImports: [][2]string{{"", "tailscale.com/types/views"}},
 		},
 		{
 			name:        "Slice",
 			content:     `type Test struct { Slice []int }`,
 			typeNames:   []string{"Test"},
-			wantImports: []string{"tailscale.com/types/views"},
+			wantImports: [][2]string{{"", "tailscale.com/types/views"}},
 		},
 	}
 	for _, tt := range tests {
@@ -68,9 +68,9 @@ func TestViewerImports(t *testing.T) {
 				genView(&output, tracker, namedType, pkg)
 			}
 
-			for _, pkgName := range tt.wantImports {
-				if !tracker.Has(pkgName) {
-					t.Errorf("missing import %q", pkgName)
+			for _, pkg := range tt.wantImports {
+				if !tracker.Has(pkg[0], pkg[1]) {
+					t.Errorf("missing import %q", pkg)
 				}
 			}
 		})