Add timestamp.valid evaluator

internal/evaluator/builder.go

@@ -235,6 +235,7 @@ func (bldr *Builder) buildValue(
 		bldr.processEnumConstraints,
 		bldr.processMapConstraints,
 		bldr.processRepeatedConstraints,
+		bldr.processTimestampConstraints,
 	}
 
 	for _, step := range steps {
@@ -464,6 +465,29 @@ func (bldr *Builder) processRepeatedConstraints(
 	return nil
 }
 
+func (bldr *Builder) processTimestampConstraints(
+	fdesc protoreflect.FieldDescriptor,
+	fieldConstraints *validate.FieldConstraints,
+	_ bool,
+	valEval *value,
+	_ MessageCache,
+) error {
+	if fdesc.Kind() != protoreflect.MessageKind ||
+		fdesc.Message().FullName() != "google.protobuf.Timestamp" {
+		return nil
+	}
+
+	secondsDesc := fdesc.Message().Fields().ByName("seconds")
+	nanosDesc := fdesc.Message().Fields().ByName("nanos")
+	timestampEval := timestampPB{
+		SecondsDescriptor: secondsDesc,
+		NanosDescriptor:   nanosDesc,
+		Valid:             fieldConstraints.GetTimestamp().GetValid(),
+	}
+	valEval.Append(timestampEval)
+	return nil
+}
+
 type MessageCache map[protoreflect.MessageDescriptor]*message
 
 func (c MessageCache) Clone() MessageCache {

internal/evaluator/timestamp.go

@@ -0,0 +1,64 @@
+// Copyright 2023 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package evaluator
+
+import (
+	"buf.build/gen/go/bufbuild/protovalidate/protocolbuffers/go/buf/validate"
+	"github.com/bufbuild/protovalidate-go/internal/errors"
+	"google.golang.org/protobuf/reflect/protoreflect"
+	"google.golang.org/protobuf/types/known/timestamppb"
+)
+
+// timestampPB is a specialized evaluator for applying some validate.TimestampRules (only the
+// `valid` rule currently) to a google.protobuf.Timestamp message. This is handled outside
+// CEL which handles google.protobuf.Timestamp as an abstract type, thus not allowing access
+// to the message fields.
+type timestampPB struct {
+	SecondsDescriptor protoreflect.FieldDescriptor
+	NanosDescriptor   protoreflect.FieldDescriptor
+	Valid             bool
+}
+
+func (t timestampPB) Evaluate(val protoreflect.Value, failFast bool) error {
+	seconds := val.Message().Get(t.SecondsDescriptor).Int()
+	nanos := val.Message().Get(t.NanosDescriptor).Int()
+
+	timestamp := &timestamppb.Timestamp{Seconds: seconds, Nanos: int32(nanos)}
+
+	err := &errors.ValidationError{Violations: []*validate.Violation{}}
+	if t.Valid {
+		terr := timestamp.CheckValid()
+		if terr != nil {
+			err.Violations = append(err.Violations, &validate.Violation{
+				ConstraintId: "timestamp.valid",
+				Message:      terr.Error(),
+			})
+			if failFast {
+				return err
+			}
+		}
+	}
+
+	if len(err.Violations) > 0 {
+		return err
+	}
+	return nil
+}
+
+func (t timestampPB) Tautology() bool {
+	return !t.Valid
+}
+
+var _ evaluator = timestampPB{}