Don't serialize args in account.ts

src/account.ts

@@ -268,16 +268,16 @@ export class Account {
     /**
      * @param contractId NEAR account where the contract is deployed
      * @param methodName The method name on the contract as it is written in the contract code
-     * @param args Any arguments to the contract method, wrapped in JSON
-     * @param data The compiled contract code
-     * @param gas An amount of yoctoⓃ attached to cover the gas cost of this function call
-     * @param amount Payment in yoctoⓃ that is sent to the contract during this function call
+     * @param args arguments to pass to method. Can be either plain JS object which gets serialized as JSON automatically
+     *  or `Uint8Array` instance which represents bytes passed as is.
+     * @param gas max amount of gas that method call can use
+      * @param deposit amount of NEAR (in yoctoNEAR) to send together with the call
      * @returns {Promise<FinalExecutionOutcome>}
      */
     async functionCall(contractId: string, methodName: string, args: any, gas?: BN, amount?: BN): Promise<FinalExecutionOutcome> {
         args = args || {};
         this.validateArgs(args);
-        return this.signAndSendTransaction(contractId, [functionCall(methodName, Buffer.from(JSON.stringify(args)), gas || DEFAULT_FUNC_CALL_GAS, amount)]);
+        return this.signAndSendTransaction(contractId, [functionCall(methodName, args, gas || DEFAULT_FUNC_CALL_GAS, amount)]);
     }
 
     /**
@@ -316,6 +316,11 @@ export class Account {
     }
 
     private validateArgs(args: any) {
+        const isUint8Array = args.byteLength !== undefined && args.byteLength === args.length;
+        if (isUint8Array) {
+            return;
+        }
+
         if (Array.isArray(args) || typeof args !== 'object') {
             throw new PositionalArgsError();
         }

src/transaction.ts

@@ -51,8 +51,20 @@ export function deployContract(code: Uint8Array): Action {
     return new Action({ deployContract: new DeployContract({code}) });
 }
 
-export function functionCall(methodName: string, args: Uint8Array, gas: BN, deposit: BN): Action {
-    return new Action({functionCall: new FunctionCall({methodName, args, gas, deposit }) });
+/**
+ * Constructs {@link Action} instance representing contract method call.
+ *
+ * @param methodName the name of the method to call
+ * @param args arguments to pass to method. Can be either plain JS object which gets serialized as JSON automatically
+ *  or `Uint8Array` instance which represents bytes passed as is.
+ * @param gas max amount of gas that method call can use
+ * @param deposit amount of NEAR (in yoctoNEAR) to send together with the call
+ */
+export function functionCall(methodName: string, args: Uint8Array | object, gas: BN, deposit: BN): Action {
+    const anyArgs = args as any;
+    const isUint8Array = anyArgs.byteLength !== undefined && anyArgs.byteLength === anyArgs.length;
+    const serializedArgs = isUint8Array ? args : Buffer.from(JSON.stringify(args));
+    return new Action({functionCall: new FunctionCall({methodName, args: serializedArgs, gas, deposit }) });
 }
 
 export function transfer(deposit: BN): Action {

test/transaction.test.js

@@ -0,0 +1,28 @@
+const { functionCall } = require('../lib/transaction');
+const BN = require('bn.js');
+
+test('functionCall with already serialized args', () => {
+    const serializedArgs = Buffer.from('{}');
+    const action = functionCall('methodName', serializedArgs, new BN(1), new BN(2));    
+    expect(action).toMatchObject({ 
+        functionCall: {
+            methodName: 'methodName',
+            args: serializedArgs,
+            gas: new BN(1),
+            deposit: new BN(2)
+        }
+    });
+});
+
+test('functionCall with non-serialized args', () => {
+    const serializedArgs = Buffer.from('{}');
+    const action = functionCall('methodName', {}, new BN(1), new BN(2));    
+    expect(action).toMatchObject({ 
+        functionCall: {
+            methodName: 'methodName',
+            args: serializedArgs,
+            gas: new BN(1),
+            deposit: new BN(2)
+        }
+    });
+});