fix: refactor createByteLengthFunction, warn if fails

src/fallback.ts

@@ -334,6 +334,20 @@ export class GrpcClient {
 
     return serviceStub;
   }
+
+  /**
+   * Creates a 'bytelength' function for a given proto message class.
+   *
+   * See {@link BundleDescriptor} about the meaning of the return value.
+   *
+   * @param {function} message - a constructor function that is generated by
+   *   protobuf.js. Assumes 'encoder' field in the message.
+   * @return {function(Object):number} - a function to compute the byte length
+   *   for an object.
+   */
+  static createByteLengthFunction(message: typeof protobuf.Message) {
+    return gax.createByteLengthFunction(message);
+  }
 }
 
 /**

src/gax.ts

@@ -18,6 +18,8 @@
  * Google API Extensions
  */
 
+import type {Message} from 'protobufjs';
+import {warn} from './warnings';
 import {BundleOptions} from './bundlingCalls/bundleExecutor';
 import {toLowerCamelCase} from './util';
 
@@ -702,3 +704,20 @@ export function constructSettings(
 
   return defaults;
 }
+
+export function createByteLengthFunction(message: typeof Message) {
+  return function getByteLength(obj: {}) {
+    try {
+      return message.encode(obj).finish().length;
+    } catch (err) {
+      const stringified = JSON.stringify(obj);
+      warn(
+        'error_encoding_protobufjs_object',
+        `Cannot encode protobuf.js object: ${stringified}: ${err}`
+      );
+      // We failed to encode the object properly, let's just return an upper boundary of its length.
+      // It's only needed for calculating the size of the batch, so it's safe if it's bigger than needed.
+      return stringified.length;
+    }
+  };
+}

src/grpc.ts

@@ -531,14 +531,8 @@ export class GrpcClient {
    * @return {function(Object):number} - a function to compute the byte length
    *   for an object.
    */
-  static createByteLengthFunction(message: {
-    encode: (obj: {}) => {
-      finish: () => Array<{}>;
-    };
-  }) {
-    return function getByteLength(obj: {}) {
-      return message.encode(obj).finish().length;
-    };
+  static createByteLengthFunction(message: typeof protobuf.Message) {
+    return gax.createByteLengthFunction(message);
   }
 }