request: log topics type could be narrowed

[0xOlias]

Is there an existing issue for this?

• I have searched the existing issues

Package Version

0.1.6

Current Behavior

Event logs returned by viem have a topics property typed like this:

type TopicFilter = (null | string | string[])[]

type Log = {
  /** List of order-dependent topics */
  topics: TopicFilter
}

Expected Behavior

While the topics property of the filter argument to RPC methods like eth_getLogs and eth_newFilter can contain elements that are an array of strings or null, I'm fairly certain that the topics property for any given Log object returned by these RPC methods will only ever contain strings (Solidity docs reference).

type Topics = string[]

type Log = {
  /** List of order-dependent topics */
  topics: Topics
}

It may be possible to narrow the type further like this:

type Hex = `0x${string}`

type Topics = [Hex, Hex | undefined, Hex | undefined, Hex | undefined]

but I'm not certain that the first topic must be defined (can an anonymous event have 0 indexed arguments?).

Steps To Reproduce

No response

Link to Minimal Reproducible Example (StackBlitz, CodeSandbox, GitHub repo etc.)

No response

Anything else?

No response

[ryandotsmith]

Yellow Paper section 4.3.1:

A log entry, $O$, is a tuple of the logger's address, $O_a$, a possibly empty series of 32-byte log topics, $O_{\mathbf{t}}$ and some number of bytes of data, $O_{\mathbf{d}}$:

$$O \equiv (O_{\mathrm{a}}, ({O_{\mathbf{t}}}0, {O{\mathbf{t}}}1, ...), O{\mathbf{d}})$$

Topics can be empty. For example: this transaction contains logs with empty topics.

[0xOlias]

Thanks! So, the best type is probably:

type Topics = Hex[];

Although it is guaranteed that the length of the array will be <= 4, and that could be represented as a union of tuples:

type Topics = [] | [Hex] | [Hex, Hex] | [Hex, Hex, Hex] | [Hex, Hex, Hex, Hex];

In any case, the current type of (null | string | string[])[] is incorrect because AFAIK topic elements will never be null and will never be string[].