Update oneof required semantics to be exactly one field passes field …

…required

proto/protovalidate-testing/buf/validate/conformance/cases/oneofs.proto

@@ -17,6 +17,7 @@ syntax = "proto3";
 package buf.validate.conformance.cases;
 
 import "buf/validate/validate.proto";
+import "google/protobuf/duration.proto";
 
 message TestOneofMsg {
   bool val = 1 [(buf.validate.field).bool.const = true];
@@ -45,6 +46,7 @@ message OneofRequired {
     int32 y = 2;
     int32 name_with_underscores = 3;
     int32 under_and_1_number = 4;
+    google.protobuf.Duration duration = 5;
   }
 }
 

proto/protovalidate/buf/validate/validate.proto

@@ -92,12 +92,12 @@ message MessageConstraints {
 
 // The `OneofConstraints` message type enables you to manage constraints for
 // oneof fields in your protobuf messages. Use the `required` constraint to ensure
-// that exactly one of the fields within a oneof is set; validation will fail
-// if none of the fields in the oneof are set:
+// that exactly one of the fields within a oneof is not empty; validation will fail
+// if all of the fields in the oneof are empty:
 message OneofConstraints {
   // `required` is an optional boolean attribute that ensures that
-  // exactly one of the field options in a oneof is set; validation fails if
-  // no fields in the oneof are set.
+  // exactly one of the field options in a oneof is not empty; validation fails if
+  // all fields in the oneof are empty.
   //
   // ```proto
   // message MyMessage {

tools/protovalidate-conformance/internal/cases/cases_oneof.go

@@ -19,6 +19,7 @@ import (
 	"github.com/bufbuild/protovalidate/tools/internal/gen/buf/validate/conformance/cases"
 	"github.com/bufbuild/protovalidate/tools/protovalidate-conformance/internal/results"
 	"github.com/bufbuild/protovalidate/tools/protovalidate-conformance/internal/suites"
+	"google.golang.org/protobuf/types/known/durationpb"
 )
 
 func oneofSuite() suites.Suite {
@@ -59,10 +60,22 @@ func oneofSuite() suites.Suite {
 			Message:  &cases.Oneof{O: &cases.Oneof_Z{Z: &cases.TestOneofMsg{}}},
 			Expected: results.Violations(&validate.Violation{FieldPath: "z.val", ConstraintId: "bool.const"}),
 		},
-		"required/valid": {
+		"required/valid_scalar": {
+			Message:  &cases.OneofRequired{O: &cases.OneofRequired_X{X: "foo"}},
+			Expected: results.Success(true),
+		},
+		"required/empty_scalar": {
 			Message:  &cases.OneofRequired{O: &cases.OneofRequired_X{X: ""}},
+			Expected: results.Violations(&validate.Violation{FieldPath: "o", ConstraintId: "required"}),
+		},
+		"required/valid_message": {
+			Message:  &cases.OneofRequired{O: &cases.OneofRequired_Duration{Duration: &durationpb.Duration{}}},
 			Expected: results.Success(true),
 		},
+		"required/empty_message": {
+			Message:  &cases.OneofRequired{O: &cases.OneofRequired_Duration{Duration: nil}},
+			Expected: results.Violations(&validate.Violation{FieldPath: "o", ConstraintId: "required"}),
+		},
 		"required/invalid": {
 			Message:  &cases.OneofRequired{},
 			Expected: results.Violations(&validate.Violation{FieldPath: "o", ConstraintId: "required"}),