`signer` should be optional when calling `toMetaMaskSmartAccount`

[jeffsmale90]

When creating a MetaMaskSmartAccount abstraction, the caller must provide a signer, so the abstraction can perform signatures.

In some cases, the caller may not have the signer available, but may still be able to derive value from the abstraction. For instance Multisig accounts with distributed signers, or a backend account deployer.

The signer argument in the toMetaMaskSmartAccount should be optional. If this argument is not specified, any function call that requires a signer should throw an error with a useful message indicating that the function is not available without a signer, and how the caller may specify the signer in order to perform signing operations.

Related to #62

[patchy-the-bot]

Hi @jeffsmale90, @mj-kiwi, I'm thinking to make the following changes:

Proposed changes

Summary

Make the signer parameter optional in toMetaMaskSmartAccount and throw descriptive errors when signer-dependent functions are called without a signer.

Approach

packages/smart-accounts-kit/src/types.ts

• Update ToMetaMaskSmartAccountParameters<TImplementation> type to make signer optional
• Change signer: SignerConfigByImplementation<TImplementation> to signer?: SignerConfigByImplementation<TImplementation>
• Update JSDoc comments to reflect that signer is now optional

packages/smart-accounts-kit/src/toMetaMaskSmartAccount.ts

• Modify resolveSigner call to handle optional signer parameter
• Update signDelegation and signUserOperation functions to check if signer exists before attempting operations
• Add descriptive error messages when signer is required but not provided:
  • "Cannot sign delegation: signer not provided. Specify a signer in toMetaMaskSmartAccount() to perform signing operations."
  • "Cannot sign user operation: signer not provided. Specify a signer in toMetaMaskSmartAccount() to perform signing operations."
• Conditionally pass signer properties to toSmartAccount only when signer is available

packages/smart-accounts-kit/src/signer.ts

• Update resolveSigner function signature to accept optional signer parameter
• Return null or undefined when signer is not provided instead of throwing errors
• Add overloaded function signatures to handle both optional and required signer cases
• Update function to gracefully handle the case where no signer is provided

packages/smart-accounts-kit/test/toMetaMaskSmartAccount.test.ts

• Add test cases for creating smart accounts without signers for each implementation
• Add test cases verifying that signing operations throw appropriate errors when no signer is provided
• Add test cases for functions that should work without a signer (like getAddress, getNonce, encodeCalls)
• Test error messages match the expected format for consistency with codebase patterns

Files to modify

• packages/smart-accounts-kit/src/types.ts
• packages/smart-accounts-kit/src/toMetaMaskSmartAccount.ts
• packages/smart-accounts-kit/src/signer.ts
• packages/smart-accounts-kit/test/toMetaMaskSmartAccount.test.ts

---

Let me know what you think with 👍 or 👎 reaction.