From 8142aa6c1da89772640f02fb15f577f2b40217cf Mon Sep 17 00:00:00 2001
From: Trent Nelson <trent@solana.com>
Date: Thu, 23 Apr 2020 15:44:19 -0600
Subject: [PATCH] feat: allow external signatures on `Transactions`

Adds a helper for adding externally created signature/pubkey pairs
to `Transactions`
---
 web3.js/module.d.ts        |  1 +
 web3.js/module.flow.js     |  1 +
 web3.js/src/transaction.js | 22 +++++++++++++++-------
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/web3.js/module.d.ts b/web3.js/module.d.ts
index 94d54a376d..e90c245667 100644
--- a/web3.js/module.d.ts
+++ b/web3.js/module.d.ts
@@ -406,6 +406,7 @@ declare module '@solana/web3.js' {
     signData: Buffer;
     sign(...signers: Array<Account>): void;
     signPartial(...partialSigners: Array<PublicKey | Account>): void;
+    addSignature(pubkey: PublicKey, signature: Buffer): void;
     addSigner(signer: Account): void;
     verifySignatures(): boolean;
     serialize(): Buffer;
diff --git a/web3.js/module.flow.js b/web3.js/module.flow.js
index fc7d90e229..93e98719f4 100644
--- a/web3.js/module.flow.js
+++ b/web3.js/module.flow.js
@@ -415,6 +415,7 @@ declare module '@solana/web3.js' {
     sign(...signers: Array<Account>): void;
     signPartial(...partialSigners: Array<PublicKey | Account>): void;
     addSigner(signer: Account): void;
+    addSignature(pubkey: PublicKey, signature: Buffer): void;
     verifySignatures(): boolean;
     serialize(): Buffer;
   }
diff --git a/web3.js/src/transaction.js b/web3.js/src/transaction.js
index a1ffeb1250..bf66d801b4 100644
--- a/web3.js/src/transaction.js
+++ b/web3.js/src/transaction.js
@@ -398,16 +398,24 @@ export class Transaction {
    * `signPartial`
    */
   addSigner(signer: Account) {
-    const index = this.signatures.findIndex(sigpair =>
-      signer.publicKey.equals(sigpair.publicKey),
-    );
-    if (index < 0) {
-      throw new Error(`Unknown signer: ${signer.publicKey.toString()}`);
-    }
-
     const signData = this.signData;
     const signature = nacl.sign.detached(signData, signer.secretKey);
+    this.addSignature(signer.publicKey, signature);
+  }
+
+  /**
+   * Add an externally created signature to a transaction
+   */
+  addSignature(pubkey: PublicKey, signature: Buffer) {
     invariant(signature.length === 64);
+
+    const index = this.signatures.findIndex(sigpair =>
+      pubkey.equals(sigpair.publicKey),
+    );
+    if (index < 0) {
+      throw new Error(`Unknown signer: ${pubkey.toString()}`);
+    }
+
     this.signatures[index].signature = Buffer.from(signature);
   }