Linter for action reads in state, function-based-actions

Is your feature request related to a problem? Please describe.
I want to be able to quickly fail should I attempt to read the wrong state item.

@action(reads=["foo"], ...)
def my_action(state: State) -> State:
    bar = state["bar"] # not in reads...
    ...

We know for sure that this should fail.

Describe the solution you'd like
A checker to warn this. We won't be able to catch all cases (for whatever reason), but given the following assumptions (that we can check for), we should be able to get it working to be correct.

The state parameter is not overwritten with another state parameter
Only strings in reads
State access is done with brackets

Then we can walk through the AST to (a) ensure this and (b) check that all state parameters if that's the case.

Describe alternatives you've considered
Having a better error message, adding that as well.

Additional context
Just developing and liked this idea

This is not an easy bit of coding (I'm sure chatGPT can help), but it's self-contained and very testable, so should be doable for most engineers.

See this claude chat to get started! https://claude.site/artifacts/502ab996-3352-4809-bd35-4a3493e1583d

@elijahbenizzy

Hey, is this still an issue? If that's the case I would like to work on it @elijahbenizzy

@elijahbenizzy

Hi @elijahbenizzy

I’d like to work on this issue if it’s still open.

I understand the goal is to statically detect undeclared state reads in function-based actions (under the assumptions listed). I’ll take some time to go through the action and state internals and come back with a concrete proposal before starting implementation.

Please let me know if that sounds good.

@elijahbenizzy

Hi @elijahbenizzy

I’d like to work on this issue if it’s still open.

Based on a quick pass through the function-based action implementation, this seems feasible via a scoped AST check:

Target FunctionBasedAction / FunctionBasedStreamingAction
Parse the source of the originating function
Detect state["<key>"] accesses with string literals
Compare against the declared reads=[...]
Fail fast when undeclared reads are detected

I’d plan to run this validation at application build time (not decorator import time) and scope it strictly to the assumptions listed in the issue.

Before starting, can you confirm:

Build-time validation is the right hook?
Hard error vs warning for the initial behavior?

Thanks!

Thanks for assigning! I’ll start implementing the AST-based validation and follow up with a PR once I have initial tests in place.

@elijahbenizzy

@elijahbenizzy
Opened PR: #656

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Linter for action reads in state, function-based-actions #407

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Linter for action reads in state, function-based-actions #407

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elijahbenizzy commented on Oct 24, 2024

fediazgon commented on Jan 13, 2026

Smitaambiger commented on Feb 9, 2026

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