chore: Refactor MDX protobuf generation to use the newer opaque api.

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)