chore: Refactor MDX protobuf generation to use the newer opaque api. (#1072)

This updates protobuf code generator to generate the newer style opaque api. This is safer to use and more in line
with other generated Google API stubs. This does not change the API structure in any way.

Author: hessjcg

build.sh

@@ -34,14 +34,19 @@ function clean() {
 ## generate - Generates all required files, before building
 function generate() {
   get_protoc
+
+  pbFile="internal/mdx/metadata_exchange.pb.go"
+  # Delete the old MDX pb file
+  rm "$pbFile"
+
   PATH="${SCRIPT_DIR}/.tools/protoc/bin:$PATH" "${SCRIPT_DIR}/.tools/protoc/bin/protoc" \
     --proto_path=. \
     --go_out=. \
+    --go_opt=default_api_level=API_OPAQUE \
     internal/mdx/metadata_exchange.proto \
     --go_opt=paths=source_relative
 
   # Add the copyright header to the generated protobuf file
-  pbFile="internal/mdx/metadata_exchange.pb.go"
   mv "${pbFile}" "${pbFile}.tmp"
   cat > "${pbFile}" <<EOF
 // Copyright 2025 Google LLC

dialer.go

@@ -835,5 +835,5 @@ func newMDXRequest(ci cloudsql.ConnectionInfo, cfg dialConfig, metadataExchangeD
 		return nil
 	}
 
-	return &mdx.MetadataExchangeRequest{ClientProtocolType: &cpt}
+	return mdx.MetadataExchangeRequest_builder{ClientProtocolType: &cpt}.Build()
 }

dialer_test.go

@@ -1752,7 +1752,7 @@ func TestNewMDXRequest(t *testing.T) {
 			cfg: dialConfig{
 				mdxClientProtocolType: cloudsql.ClientProtocolTCP,
 			},
-			want: &mdx.MetadataExchangeRequest{ClientProtocolType: &tcp},
+			want: mdx.MetadataExchangeRequest_builder{ClientProtocolType: &tcp}.Build(),
 		},
 		{
 			desc: "when client protocol is CLIENT_PROTOCOL_UDS",
@@ -1762,7 +1762,7 @@ func TestNewMDXRequest(t *testing.T) {
 			cfg: dialConfig{
 				mdxClientProtocolType: cloudsql.ClientProtocolUDS,
 			},
-			want: &mdx.MetadataExchangeRequest{ClientProtocolType: &uds},
+			want: mdx.MetadataExchangeRequest_builder{ClientProtocolType: &uds}.Build(),
 		},
 		{
 			desc: "when client protocol is CLIENT_PROTOCOL_TLS",
@@ -1772,7 +1772,7 @@ func TestNewMDXRequest(t *testing.T) {
 			cfg: dialConfig{
 				mdxClientProtocolType: cloudsql.ClientProtocolTLS,
 			},
-			want: &mdx.MetadataExchangeRequest{ClientProtocolType: &tlsRes},
+			want: mdx.MetadataExchangeRequest_builder{ClientProtocolType: &tlsRes}.Build(),
 		},
 	}
 

internal/cloudsql/metadataexchange.go

@@ -196,23 +196,19 @@ func (c *MDXConn) readMDX() (*mdx.MetadataExchangeResponse, error) {
 
 // IsResponseOk returns true if a response was received and ResponseStatusCode == OK.
 func (c *MDXConn) IsResponseOk() bool {
-	return c.res.ResponseStatusCode != nil &&
-		*c.res.ResponseStatusCode == mdx.MetadataExchangeResponse_OK
+	return c.res.GetResponseStatusCode() == mdx.MetadataExchangeResponse_OK
 }
 
 // GetErrorMessage returns the ErrorMessage in the MDX Response.
 func (c *MDXConn) GetErrorMessage() string {
-	if c.res.ErrorMessage != nil {
-		return *c.res.ErrorMessage
-	}
-	return ""
+	return c.res.GetErrorMessage()
 }
 
 // writeMDX writes the MDX response back to the socket.
 func (c *MDXConn) writeMDX(req *mdx.MetadataExchangeRequest) error {
 	// ctx only used for debug logging
 	ctx := context.Background()
-	c.logger.Debugf(ctx, "[%v] Writing MDX request, protocol:%v...", c.cn, req.ClientProtocolType)
+	c.logger.Debugf(ctx, "[%v] Writing MDX request, protocol:%v...", c.cn, req.GetClientProtocolType())
 
 	buf := buffPool.get()
 	defer buffPool.put(buf)

internal/cloudsql/metadataexchange_test.go

@@ -65,9 +65,9 @@ func newFakeConn(bytesToRead []byte) *fakeConn {
 }
 
 func newMDXResponseBytes(data []byte) (*mdx.MetadataExchangeResponse, []byte) {
-	res := &mdx.MetadataExchangeResponse{
+	res := mdx.MetadataExchangeResponse_builder{
 		ResponseStatusCode: ptr(mdx.MetadataExchangeResponse_OK),
-	}
+	}.Build()
 	resBytes, err := proto.Marshal(res)
 	if err != nil {
 		panic(err)
@@ -82,7 +82,9 @@ func newMDXResponseBytes(data []byte) (*mdx.MetadataExchangeResponse, []byte) {
 }
 
 func newMDXRequestBytes(data []byte) (*mdx.MetadataExchangeRequest, []byte) {
-	req := &mdx.MetadataExchangeRequest{UserAgent: proto.String("hello")}
+	req := mdx.MetadataExchangeRequest_builder{
+		UserAgent: proto.String("hello"),
+	}.Build()
 	resBytes, err := proto.Marshal(req)
 	if err != nil {
 		panic(err)
@@ -195,9 +197,9 @@ func TestMDXConn_Request_Response_WriteRead(t *testing.T) {
 	if !mdxConn.HasMDXResponse() {
 		t.Fatalf("expected no MDX response, got response")
 	}
-	if *mdxConn.GetMDXResponse().ResponseStatusCode != *res.ResponseStatusCode {
+	if mdxConn.GetMDXResponse().GetResponseStatusCode() != res.GetResponseStatusCode() {
 		t.Fatalf("expected status code %v, got %v",
-			res.ResponseStatusCode, mdxConn.GetMDXResponse().ResponseStatusCode)
+			res.GetResponseStatusCode(), mdxConn.GetMDXResponse().GetResponseStatusCode())
 	}
 }
 
@@ -216,9 +218,9 @@ func TestMDXConn_Request_Response_ReadWrite(t *testing.T) {
 	if !mdxConn.HasMDXResponse() {
 		t.Fatalf("expected no MDX response, got response")
 	}
-	if *mdxConn.GetMDXResponse().ResponseStatusCode != *res.ResponseStatusCode {
+	if mdxConn.GetMDXResponse().GetResponseStatusCode() != res.GetResponseStatusCode() {
 		t.Fatalf("expected status code %v, got %v",
-			res.ResponseStatusCode, mdxConn.GetMDXResponse().ResponseStatusCode)
+			res.GetResponseStatusCode(), mdxConn.GetMDXResponse().GetResponseStatusCode())
 	}
 }