Incompatibility in AbstractSigner: sendTransaction Passes Transaction with Private Properties to signTransaction Expecting TransactionRequest with Unresolved Properties

[taylorjdawson]

In upgrading from v5 to v6, I had to override sendTransaction due to a nuanced type issue between AbstractSigner and Transaction.

The core of the issue is that sendTransaction generates a Transaction instance via Transaction.from(), which is then passed to signTransaction.

Although signTransaction is designed to accept a TransactionRequest, the structural similarities between TransactionRequest and Transaction mean TypeScript doesn't identify this as an error, despite a crucial difference: Transaction's properties are private.

This distinction becomes problematic when resolveProperties is invoked on the TransactionRequest within signTransaction, leading to an empty object because Object.keys() cannot access Transaction's private properties.

Importantly, TransactionRequest may contain properties as promises, necessitating the use of resolveProperties to ensure proper handling.

This subtlety in how Transaction instances and TransactionRequest objects are treated, especially regarding promise properties and the need for resolveProperties, indicates a potential area for improvement in ethers library's type system.

Either the AbstractSigner's sendTransaction implementation needs to pass in the appropriate type to signTransaction or signTransaction's param type needs to be updated such that the developer implementing a customer signer is aware that an instance of Transaction may be passed to it.

My current solution is to override the sendTransaction method but this came after hours of trying to figure out why the signature was different between calling signTransaction and the signature produced after calling sendTransaction.