add error

schema/errors.go

@@ -0,0 +1,20 @@
+// Copyright © 2024 Meroxa, 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 schema
+
+import "errors"
+
+// errInvalidProtoIsNil is returned when trying to convert a proto schema to a schema object.
+var errInvalidProtoIsNil = errors.New("invalid proto: nil")

schema/proto.go

@@ -14,7 +14,9 @@
 
 package schema
 
-import schemav1 "github.com/conduitio/conduit-commons/proto/schema/v1"
+import (
+	schemav1 "github.com/conduitio/conduit-commons/proto/schema/v1"
+)
 
 func _() {
 	// An "invalid array index" compiler error signifies that the constant values have changed.
@@ -49,7 +51,7 @@ func (s *Schema) FromProto(proto *schemav1.Schema) error {
 // populated.
 func (s *Schema) ToProto(proto *schemav1.Schema) error {
 	if proto == nil {
-		return nil
+		return errInvalidProtoIsNil
 	}
 
 	proto.Subject = s.Subject

schema/proto_test.go

@@ -47,22 +47,49 @@ func TestSchema_FromProto(t *testing.T) {
 func TestSchema_ToProto(t *testing.T) {
 	is := is.New(t)
 
-	s1 := Schema{
-		Subject: "subject",
-		Version: 1,
-		Type:    TypeAvro,
-		Bytes:   []byte("bytes"),
+	testCases := []struct {
+		name    string
+		in      *schemav1.Schema
+		want    *schemav1.Schema
+		wantErr error
+	}{
+		{
+			name:    "when proto object is nil",
+			in:      nil,
+			want:    nil,
+			wantErr: errInvalidProtoIsNil,
+		},
+		{
+			name: "when proto object is not nil",
+			in:   &schemav1.Schema{},
+			want: &schemav1.Schema{
+				Subject: "subject",
+				Version: 1,
+				Type:    schemav1.Schema_TYPE_AVRO,
+				Bytes:   []byte("bytes"),
+			},
+		},
 	}
 
-	want := &schemav1.Schema{
-		Subject: s1.Subject,
-		Version: 1,
-		Type:    schemav1.Schema_TYPE_AVRO,
-		Bytes:   s1.Bytes,
-	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			is := is.New(t)
 
-	var got schemav1.Schema
-	err := s1.ToProto(&got)
-	is.NoErr(err)
-	is.Equal(&got, want)
+			s1 := Schema{
+				Subject: "subject",
+				Version: 1,
+				Type:    TypeAvro,
+				Bytes:   []byte("bytes"),
+			}
+
+			err := s1.ToProto(tc.in)
+
+			if tc.wantErr == nil {
+				is.NoErr(err)
+				is.Equal(tc.in, tc.want)
+			} else {
+				is.Equal(err.Error(), tc.wantErr.Error())
+			}
+		})
+	}
 }