Fix getAccountsWithOptionalFeePayer

packages/solana/lib/src/encoder/extensions.dart

@@ -71,14 +71,22 @@ extension InstructionListExt on List<Instruction> {
   List<AccountMeta> getAccountsWithOptionalFeePayer({
     String? feePayer,
   }) {
+    final programIds = <String>[];
     final accounts = expand<AccountMeta>(
-      (Instruction instruction) => [
-        ...instruction.accounts,
-
-        /// Append the instruction program id
-        AccountMeta.readonly(pubKey: instruction.programId, isSigner: false),
-      ],
+      (Instruction instruction) {
+        /// Store instruction programId
+        if (!programIds.contains(instruction.programId)) {
+          programIds.add(instruction.programId);
+        }
+        return instruction.accounts;
+      },
     ).toList();
+
+    /// Append programIds to accounts (at the end)
+    for (final programId in programIds) {
+      accounts.add(AccountMeta.readonly(pubKey: programId, isSigner: false));
+    }
+
     if (feePayer != null) {
       final index = accounts.indexWhere(
         (AccountMeta account) => account.pubKey == feePayer,

packages/solana/test/instruction_test.dart

@@ -0,0 +1,43 @@
+import 'package:solana/encoder.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('Account metas are correctly sorted', () {
+    final accounts = _instructionList.getAccountsWithOptionalFeePayer(
+        feePayer: '9KaA7vEBUdRCcBWxfuMjxYwKfvu8Us3Cg5gkhVFt2LNk');
+    for (var i = 0; i < accounts.length; i++) {
+      expect(accounts[i].pubKey, equals(_expectedResult[i]));
+    }
+  });
+}
+
+final _instructionList = [
+  Instruction(
+    programId: '6KR4qkJN91LGko2gdizheri8LMtCwsJrhtsQt6QPwCi5',
+    accounts: [
+      AccountMeta(
+          pubKey: 'JBm16mKFNXotwiYjdGuVJcLBeuJdQkT84aNBNhnakToW',
+          isWriteable: false,
+          isSigner: false),
+    ],
+    data: [],
+  ),
+  Instruction(
+    programId: 'DAz7SnxRL2HRZ2GPigdVRGkoF39bD4Qdv8td5wD3i35u',
+    accounts: [
+      AccountMeta(
+          pubKey: '2qXtx3xmmmJyA64vrszWAqSXEvYaQNAo1yL4tCxBYPZv',
+          isWriteable: false,
+          isSigner: false),
+    ],
+    data: [],
+  ),
+];
+
+final _expectedResult = [
+  '9KaA7vEBUdRCcBWxfuMjxYwKfvu8Us3Cg5gkhVFt2LNk',
+  'JBm16mKFNXotwiYjdGuVJcLBeuJdQkT84aNBNhnakToW',
+  '2qXtx3xmmmJyA64vrszWAqSXEvYaQNAo1yL4tCxBYPZv',
+  '6KR4qkJN91LGko2gdizheri8LMtCwsJrhtsQt6QPwCi5',
+  'DAz7SnxRL2HRZ2GPigdVRGkoF39bD4Qdv8td5wD3i35u',
+];