FindStructTypeFields support for types.Provider (#814)

cel/env.go

@@ -773,6 +773,13 @@ func (p *interopCELTypeProvider) FindStructType(typeName string) (*types.Type, b
 	return nil, false
 }
 
+// FindStructFieldNames returns an empty set of field for the interop provider.
+//
+// To inspect the field names, migrate to a `types.Provider` implementation.
+func (p *interopCELTypeProvider) FindStructFieldNames(typeName string) ([]string, bool) {
+	return []string{}, false
+}
+
 // FindStructFieldType returns a types.FieldType instance for the given fully-qualified typeName and field
 // name, if one exists.
 //

cel/env_test.go

@@ -385,6 +385,10 @@ func (p *customCELProvider) FindStructType(typeName string) (*types.Type, bool)
 	return p.provider.FindStructType(typeName)
 }
 
+func (p *customCELProvider) FindStructFieldNames(typeName string) ([]string, bool) {
+	return p.provider.FindStructFieldNames(typeName)
+}
+
 func (p *customCELProvider) FindStructFieldType(structType, fieldName string) (*types.FieldType, bool) {
 	return p.provider.FindStructFieldType(structType, fieldName)
 }

common/types/provider.go

@@ -54,6 +54,10 @@ type Provider interface {
 	// Returns false if not found.
 	FindStructType(structType string) (*Type, bool)
 
+	// FindStructFieldNames returns thet field names associated with the type, if the type
+	// is found.
+	FindStructFieldNames(structType string) ([]string, bool)
+
 	// FieldStructFieldType returns the field type for a checked type value. Returns
 	// false if the field could not be found.
 	FindStructFieldType(structType, fieldName string) (*FieldType, bool)
@@ -173,6 +177,23 @@ func (p *Registry) FindFieldType(structType, fieldName string) (*ref.FieldType,
 		GetFrom: field.GetFrom}, true
 }
 
+// FindStructFieldNames returns the set of field names for the given struct type,
+// if the type exists in the registry.
+func (p *Registry) FindStructFieldNames(structType string) ([]string, bool) {
+	msgType, found := p.pbdb.DescribeType(structType)
+	if !found {
+		return []string{}, false
+	}
+	fieldMap := msgType.FieldMap()
+	fields := make([]string, len(fieldMap))
+	idx := 0
+	for f := range fieldMap {
+		fields[idx] = f
+		idx++
+	}
+	return fields, true
+}
+
 // FindStructFieldType returns the field type for a checked type value. Returns
 // false if the field could not be found.
 func (p *Registry) FindStructFieldType(structType, fieldName string) (*FieldType, bool) {

common/types/provider_test.go

@@ -18,6 +18,7 @@ import (
 	"bytes"
 	"fmt"
 	"reflect"
+	"sort"
 	"strings"
 	"testing"
 	"time"
@@ -132,6 +133,39 @@ func TestRegistryFindStructType(t *testing.T) {
 	}
 }
 
+func TestRegistryFindStructFieldNames(t *testing.T) {
+	reg := newTestRegistry(t, &exprpb.Decl{}, &exprpb.Reference{})
+	tests := []struct {
+		typeName string
+		fields   []string
+	}{
+		{
+			typeName: "google.api.expr.v1alpha1.Reference",
+			fields:   []string{"name", "overload_id", "value"},
+		},
+		{
+			typeName: "google.api.expr.v1alpha1.Decl",
+			fields:   []string{"name", "ident", "function"},
+		},
+		{
+			typeName: "invalid.TypeName",
+			fields:   []string{},
+		},
+	}
+
+	for _, tst := range tests {
+		tc := tst
+		t.Run(fmt.Sprintf("%s", tc.typeName), func(t *testing.T) {
+			fields, _ := reg.FindStructFieldNames(tc.typeName)
+			sort.Strings(fields)
+			sort.Strings(tc.fields)
+			if !reflect.DeepEqual(fields, tc.fields) {
+				t.Errorf("got %v, wanted %v", fields, tc.fields)
+			}
+		})
+	}
+}
+
 func TestRegistryFindStructFieldType(t *testing.T) {
 	reg := newTestRegistry(t)
 	err := reg.RegisterDescriptor(proto3pb.GlobalEnum_GOO.Descriptor().ParentFile())

ext/native.go

@@ -151,6 +151,24 @@ func (tp *nativeTypeProvider) FindStructType(typeName string) (*types.Type, bool
 	return tp.baseProvider.FindStructType(typeName)
 }
 
+// FindStructFieldNames looks up the type definition first from the native types, then from
+// the backing provider type set. If found, a set of field names corresponding to the type
+// will be returned.
+func (tp *nativeTypeProvider) FindStructFieldNames(typeName string) ([]string, bool) {
+	if t, found := tp.nativeTypes[typeName]; found {
+		fieldCount := t.refType.NumField()
+		fields := make([]string, fieldCount)
+		for i := 0; i < fieldCount; i++ {
+			fields[i] = t.refType.Field(i).Name
+		}
+		return fields, true
+	}
+	if celTypeFields, found := tp.baseProvider.FindStructFieldNames(typeName); found {
+		return celTypeFields, true
+	}
+	return tp.baseProvider.FindStructFieldNames(typeName)
+}
+
 // FindStructFieldType looks up a native type's field definition, and if the type name is not a native
 // type then proxies to the composed types.Provider
 func (tp *nativeTypeProvider) FindStructFieldType(typeName, fieldName string) (*types.FieldType, bool) {

ext/native_test.go

@@ -17,6 +17,7 @@ package ext
 import (
 	"fmt"
 	"reflect"
+	"sort"
 	"strings"
 	"testing"
 	"time"
@@ -162,6 +163,40 @@ func TestNativeTypes(t *testing.T) {
 	}
 }
 
+func TestNativeFindStructFieldNames(t *testing.T) {
+	env := testNativeEnv(t)
+	provider := env.CELTypeProvider()
+	tests := []struct {
+		typeName string
+		fields   []string
+	}{
+		{
+			typeName: "ext.TestNestedType",
+			fields:   []string{"NestedListVal", "NestedMapVal"},
+		},
+		{
+			typeName: "google.expr.proto3.test.TestAllTypes.NestedMessage",
+			fields:   []string{"bb"},
+		},
+		{
+			typeName: "invalid.TypeName",
+			fields:   []string{},
+		},
+	}
+
+	for _, tst := range tests {
+		tc := tst
+		t.Run(fmt.Sprintf("%s", tc.typeName), func(t *testing.T) {
+			fields, _ := provider.FindStructFieldNames(tc.typeName)
+			sort.Strings(fields)
+			sort.Strings(tc.fields)
+			if !reflect.DeepEqual(fields, tc.fields) {
+				t.Errorf("got %v, wanted %v", fields, tc.fields)
+			}
+		})
+	}
+}
+
 func TestNativeTypesStaticErrors(t *testing.T) {
 	var nativeTests = []struct {
 		expr string