web3.js: Implement addSignature in VersionedTransaction

[vsakos]

Problem

Unlike the legacy Transaction class, the new VersionedTransaction class has no addSignature() function to add signatures that were generated externally (by a third party library, browser extension etc.).

Summary of Changes

Implemented addSignature(publicKey: PublicKey, signature: Uint8Array)

[codecov]

Codecov Report

Merging #27945 (7601207) into master (e6687b8) will increase coverage by 0.4%.
The diff coverage is 96.6%.

@@            Coverage Diff            @@
##           master   #27945     +/-   ##
=========================================
+ Coverage    77.3%    77.7%   +0.4%     
=========================================
  Files          55       55             
  Lines        2889     2916     +27     
  Branches      402      404      +2     
=========================================
+ Hits         2234     2267     +33     
+ Misses        514      509      -5     
+ Partials      141      140      -1     

[steveluscher]

Thanks for this! Let's get some tests written to cover this functionality and the invariants you want to trip, and let's ship it – unless @jstarry has additional thoughts.

Pull request has been modified.

[vsakos]

@steveluscher Pushed the updated error for invalid signers, added the check for signature length and a test.

[steveluscher]

For sure want these to be separate tests, so that when they fail, the reader doesn't have to dig to find out what functionality was broken.

describe('addSignature', () => {
  it('appends an externally generated signature at the correct index', () => { /* ... */ })
  it('fatals when the signature is the wrong length', () => { /* ... */ })
  it('fatals when adding a signature for a public key that has not been marked as a signer', () => { /* ... */ })
});

Pull request has been modified.

[vsakos]

@steveluscher I created a VersionedTransaction group with separate tests for addSignature (using the same transaction instance). What do you think of this?

[steveluscher]

Thank you!