fix: support serialization of partially signed transactions

web3.js/module.d.ts

@@ -617,6 +617,11 @@ declare module '@solana/web3.js' {
     signatures?: Array<SignaturePubkeyPair>;
   };
 
+  export type SerializeConfig = {
+    requireAllSignatures?: boolean;
+    verifySignatures?: boolean;
+  };
+
   export class Transaction {
     signatures: Array<SignaturePubkeyPair>;
     signature?: Buffer;
@@ -640,7 +645,7 @@ declare module '@solana/web3.js' {
     addSignature(pubkey: PublicKey, signature: Buffer): void;
     setSigners(...signer: Array<PublicKey>): void;
     verifySignatures(): boolean;
-    serialize(): Buffer;
+    serialize(config?: SerializeConfig): Buffer;
   }
 
   // === src/stake-program.js ===

web3.js/module.flow.js

@@ -621,6 +621,11 @@ declare module '@solana/web3.js' {
     signatures?: Array<SignaturePubkeyPair>,
   |};
 
+  declare export type SerializeConfig = {
+    requireAllSignatures?: boolean,
+    verifySignatures?: boolean,
+  };
+
   declare export class Transaction {
     signatures: Array<SignaturePubkeyPair>;
     signature: ?Buffer;
@@ -644,7 +649,7 @@ declare module '@solana/web3.js' {
     addSignature(pubkey: PublicKey, signature: Buffer): void;
     setSigners(...signers: Array<PublicKey>): void;
     verifySignatures(): boolean;
-    serialize(): Buffer;
+    serialize(config?: SerializeConfig): Buffer;
   }
 
   // === src/stake-program.js ===

web3.js/src/transaction.js

@@ -62,6 +62,18 @@ export type TransactionInstructionCtorFields = {|
   data?: Buffer,
 |};
 
+/**
+ * Configuration object for Transaction.serialize()
+ *
+ * @typedef {Object} SerializeConfig
+ * @property {boolean|undefined} requireAllSignatures Require all transaction signatures be present (default: true)
+ * @property {boolean|undefined} verifySignatures Verify provided signatures (default: true)
+ */
+export type SerializeConfig = {
+  requireAllSignatures?: boolean,
+  verifySignatures?: boolean,
+};
+
 /**
  * Transaction Instruction class
  */
@@ -462,37 +474,49 @@ export class Transaction {
    * Verify signatures of a complete, signed Transaction
    */
   verifySignatures(): boolean {
-    return this._verifySignatures(this.serializeMessage());
+    return this._verifySignatures(this.serializeMessage(), true);
   }
 
   /**
    * @private
    */
-  _verifySignatures(signData: Buffer): boolean {
-    let verified = true;
+  _verifySignatures(signData: Buffer, requireAllSignatures: boolean): boolean {
     for (const {signature, publicKey} of this.signatures) {
-      if (
-        !nacl.sign.detached.verify(signData, signature, publicKey.toBuffer())
-      ) {
-        verified = false;
+      if (signature === null) {
+        if (requireAllSignatures) {
+          return false;
+        }
+      } else {
+        if (
+          !nacl.sign.detached.verify(signData, signature, publicKey.toBuffer())
+        ) {
+          return false;
+        }
       }
     }
-    return verified;
+    return true;
   }
 
   /**
    * Serialize the Transaction in the wire format.
-   *
-   * The Transaction must have a valid `signature` before invoking this method
    */
-  serialize(): Buffer {
+  serialize(config?: SerializeConfig): Buffer {
     const {signatures} = this;
-    if (!signatures || signatures.length === 0) {
+
+    const {requireAllSignatures, verifySignatures} = Object.assign(
+      {requireAllSignatures: true, verifySignatures: true},
+      config,
+    );
+
+    if (requireAllSignatures && signatures.length === 0) {
       throw new Error('Transaction has not been signed');
     }
 
     const signData = this.serializeMessage();
-    if (!this._verifySignatures(signData)) {
+    if (
+      verifySignatures &&
+      !this._verifySignatures(signData, requireAllSignatures)
+    ) {
       throw new Error('Transaction has not been signed correctly');
     }
 

web3.js/test/transaction.test.js

@@ -136,9 +136,41 @@ test('partialSign', () => {
   partialTransaction.setSigners(account1.publicKey, account2.publicKey);
   expect(partialTransaction.signatures[0].signature).toBeNull();
   expect(partialTransaction.signatures[1].signature).toBeNull();
-  partialTransaction.partialSign(account1, account2);
+
+  partialTransaction.partialSign(account1);
+  expect(partialTransaction.signatures[0].signature).not.toBeNull();
+  expect(partialTransaction.signatures[1].signature).toBeNull();
+
+  expect(() => partialTransaction.serialize()).toThrow();
+  expect(() =>
+    partialTransaction.serialize({requireAllSignatures: false}),
+  ).not.toThrow();
+
+  partialTransaction.partialSign(account2);
+
+  expect(partialTransaction.signatures[0].signature).not.toBeNull();
+  expect(partialTransaction.signatures[1].signature).not.toBeNull();
+
+  expect(() => partialTransaction.serialize()).not.toThrow();
 
   expect(partialTransaction).toEqual(transaction);
+
+  if (
+    partialTransaction.signatures[0].signature != null /* <-- pacify flow */
+  ) {
+    partialTransaction.signatures[0].signature[0] = 0;
+    expect(() =>
+      partialTransaction.serialize({requireAllSignatures: false}),
+    ).toThrow();
+    expect(() =>
+      partialTransaction.serialize({
+        verifySignatures: false,
+        requireAllSignatures: false,
+      }),
+    ).not.toThrow();
+  } else {
+    throw new Error('unreachable');
+  }
 });
 
 describe('dedupe', () => {
@@ -392,6 +424,9 @@ test('serialize unsigned transaction', () => {
   expect(() => {
     expectedTransaction.serialize();
   }).toThrow(Error);
+  expect(() => {
+    expectedTransaction.serialize({verifySignatures: false});
+  }).toThrow(Error);
   expect(() => {
     expectedTransaction.serializeMessage();
   }).toThrow('Transaction feePayer required');
@@ -407,6 +442,18 @@ test('serialize unsigned transaction', () => {
   // Serializing the message is allowed when signature array has null signatures
   expectedTransaction.serializeMessage();
 
+  const expectedSerializationWithNoSignatures = Buffer.from(
+    'AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' +
+      'AAAAAAAAAAAAAAAAAAABAAEDE5j2LG0aRXxRumpLXz29L2n8qTIWIY3ImX5Ba9F9k8r9' +
+      'Q5/Mtmcn8onFxt47xKj+XdXXd3C8j/FcPu7csUrz/AAAAAAAAAAAAAAAAAAAAAAAAAAA' +
+      'AAAAAAAAAAAAAAAAxJrndgN4IFTxep3s6kO0ROug7bEsbx0xxuDkqEvwUusBAgIAAQwC' +
+      'AAAAMQAAAAAAAAA=',
+    'base64',
+  );
+  expect(
+    expectedTransaction.serialize({requireAllSignatures: false}),
+  ).toStrictEqual(expectedSerializationWithNoSignatures);
+
   // Properly signed transaction succeeds
   expectedTransaction.partialSign(sender);
   expect(expectedTransaction.signatures.length).toBe(1);