Aliter: Implement DeliverMax alias in Payment transactions, through autofill method

packages/xrpl/src/client/index.ts

@@ -645,8 +645,8 @@ class Client extends EventEmitter<EventTypes> {
   ): Promise<T> {
     const tx = { ...transaction }
 
+    // the below two functions accept only Transaction objects.
     setValidAddresses(tx)
-
     setTransactionFlagsToNumber(tx)
 
     const promises: Array<Promise<void>> = []
@@ -666,7 +666,35 @@ class Client extends EventEmitter<EventTypes> {
       promises.push(checkAccountDeleteBlockers(this, tx))
     }
 
-    return Promise.all(promises).then(() => tx)
+    // further manipulation of tx_ uses non-SubmittableTransaction types, hence we need a typecast to any
+    let tx_ = tx as any
+
+    if (tx_.TransactionType === 'Payment') {
+      if (tx_.Amount == null) {
+        // If only DeliverMax is provided, use it to populate the Amount field
+        if (tx_.DeliverMax != null) {
+          tx_.Amount = tx_.DeliverMax
+        }
+      }
+
+      // If Amount is not identical to DeliverMax, throw an error
+      if (
+        tx_.DeliverMax != null &&
+        tx_.Amount != null &&
+        tx_.Amount !== tx_.DeliverMax
+      ) {
+        throw new ValidationError(
+          'PaymentTransaction: Amount and DeliverMax fields must be identical',
+        )
+      }
+
+      // remove the DeliverMax field
+      if (tx_.DeliverMax != null) {
+        delete tx_.DeliverMax
+      }
+    }
+
+    return Promise.all(promises).then(() => tx_)
   }
 
   /**

packages/xrpl/test/client/autofill.test.ts

@@ -7,6 +7,7 @@ import {
   Payment,
   Transaction,
 } from '../../src'
+import { ValidationError } from '../../src/errors'
 import rippled from '../fixtures/rippled'
 import {
   setupClient,
@@ -46,6 +47,121 @@ describe('client.autofill', function () {
   })
   afterEach(async () => teardownClient(testContext))
 
+  it('Validate Payment transaction v2 API: Payment Transaction: Specify Only Amount field', async function () {
+    const amount_ = '1234'
+    const paytxn = {
+      TransactionType: 'Payment',
+      Account: 'rUn84CUYbNjRoTQ6mSW7BVJPSVJNLb1QLo',
+      Amount: amount_,
+      Destination: 'rfkE1aSy9G8Upk4JssnwBxhEv5p4mn2KTy',
+      DestinationTag: 1,
+      Fee: '12',
+      Flags: 2147483648,
+      LastLedgerSequence: 65953073,
+      Sequence: 65923914,
+      SigningPubKey:
+        '02F9E33F16DF9507705EC954E3F94EB5F10D1FC4A354606DBE6297DBB1096FE654',
+      TxnSignature:
+        '3045022100E3FAE0EDEC3D6A8FF6D81BC9CF8288A61B7EEDE8071E90FF9314CB4621058D10022043545CF631706D700CEE65A1DB83EFDD185413808292D9D90F14D87D3DC2D8CB',
+      InvoiceID:
+        '6F1DFD1D0FE8A32E40E1F2C05CF1C15545BAB56B617F9C6C2D63A6B704BEF59B',
+      Paths: [
+        [{ currency: 'BTC', issuer: 'r9vbV3EHvXWjSkeQ6CAcYVPGeq7TuiXY2X' }],
+      ],
+      SendMax: '100000000',
+    } as any
+    const txResult = await testContext.client.autofill(paytxn)
+
+    assert.strictEqual(txResult.Amount, amount_)
+  })
+
+  it('Validate Payment transaction v2 API: Payment Transaction: Specify Only DeliverMax field', async function () {
+    const amount_ = '1234'
+    const paytxn = {
+      TransactionType: 'Payment',
+      Account: 'rUn84CUYbNjRoTQ6mSW7BVJPSVJNLb1QLo',
+      DeliverMax: amount_,
+      Destination: 'rfkE1aSy9G8Upk4JssnwBxhEv5p4mn2KTy',
+      DestinationTag: 1,
+      Fee: '12',
+      Flags: 2147483648,
+      LastLedgerSequence: 65953073,
+      Sequence: 65923914,
+      SigningPubKey:
+        '02F9E33F16DF9507705EC954E3F94EB5F10D1FC4A354606DBE6297DBB1096FE654',
+      TxnSignature:
+        '3045022100E3FAE0EDEC3D6A8FF6D81BC9CF8288A61B7EEDE8071E90FF9314CB4621058D10022043545CF631706D700CEE65A1DB83EFDD185413808292D9D90F14D87D3DC2D8CB',
+      InvoiceID:
+        '6F1DFD1D0FE8A32E40E1F2C05CF1C15545BAB56B617F9C6C2D63A6B704BEF59B',
+      Paths: [
+        [{ currency: 'BTC', issuer: 'r9vbV3EHvXWjSkeQ6CAcYVPGeq7TuiXY2X' }],
+      ],
+      SendMax: '100000000',
+    } as any
+    const txResult = await testContext.client.autofill(paytxn)
+
+    assert.strictEqual(txResult.Amount, amount_)
+  })
+
+  it('Validate Payment transaction v2 API: Payment Transaction: identical DeliverMax and Amount fields', async function () {
+    const amount_ = '1234'
+    const paytxn = {
+      TransactionType: 'Payment',
+      Account: 'rUn84CUYbNjRoTQ6mSW7BVJPSVJNLb1QLo',
+      DeliverMax: amount_,
+      Amount: amount_,
+      Destination: 'rfkE1aSy9G8Upk4JssnwBxhEv5p4mn2KTy',
+      DestinationTag: 1,
+      Fee: '12',
+      Flags: 2147483648,
+      LastLedgerSequence: 65953073,
+      Sequence: 65923914,
+      SigningPubKey:
+        '02F9E33F16DF9507705EC954E3F94EB5F10D1FC4A354606DBE6297DBB1096FE654',
+      TxnSignature:
+        '3045022100E3FAE0EDEC3D6A8FF6D81BC9CF8288A61B7EEDE8071E90FF9314CB4621058D10022043545CF631706D700CEE65A1DB83EFDD185413808292D9D90F14D87D3DC2D8CB',
+      InvoiceID:
+        '6F1DFD1D0FE8A32E40E1F2C05CF1C15545BAB56B617F9C6C2D63A6B704BEF59B',
+      Paths: [
+        [{ currency: 'BTC', issuer: 'r9vbV3EHvXWjSkeQ6CAcYVPGeq7TuiXY2X' }],
+      ],
+      SendMax: '100000000',
+    } as any
+    const txResult = await testContext.client.autofill(paytxn)
+
+    assert.strictEqual(txResult.Amount, amount_)
+    assert.strictEqual('DeliverMax' in txResult, false)
+  })
+
+  it('Validate Payment transaction v2 API: Payment Transaction: differing DeliverMax and Amount fields', async function () {
+    const amount_ = '1234'
+    const deliverMax_ = '5678'
+    const paytxn = {
+      TransactionType: 'Payment',
+      Account: 'rUn84CUYbNjRoTQ6mSW7BVJPSVJNLb1QLo',
+      DeliverMax: deliverMax_,
+      Amount: amount_,
+      Destination: 'rfkE1aSy9G8Upk4JssnwBxhEv5p4mn2KTy',
+      DestinationTag: 1,
+      Fee: '12',
+      Flags: 2147483648,
+      LastLedgerSequence: 65953073,
+      Sequence: 65923914,
+      SigningPubKey:
+        '02F9E33F16DF9507705EC954E3F94EB5F10D1FC4A354606DBE6297DBB1096FE654',
+      TxnSignature:
+        '3045022100E3FAE0EDEC3D6A8FF6D81BC9CF8288A61B7EEDE8071E90FF9314CB4621058D10022043545CF631706D700CEE65A1DB83EFDD185413808292D9D90F14D87D3DC2D8CB',
+      InvoiceID:
+        '6F1DFD1D0FE8A32E40E1F2C05CF1C15545BAB56B617F9C6C2D63A6B704BEF59B',
+      Paths: [
+        [{ currency: 'BTC', issuer: 'r9vbV3EHvXWjSkeQ6CAcYVPGeq7TuiXY2X' }],
+      ],
+      SendMax: '100000000',
+    } as any
+
+    await assertRejects(testContext.client.autofill(paytxn), ValidationError)
+  })
+
   it('should not autofill if fields are present', async function () {
     const tx: Transaction = {
       TransactionType: 'DepositPreauth',