Allow listeners passed into runtime.onMessage.addListener to return void

[namukang]

Previously, listeners for runtime.onMessage.addListener could return Promise<unknown> | true | void:

webextension-polyfill-ts/out/namespaces/runtime.d.ts

Line 584 in b6e8bd1

) => Promise<unknown> | true | void

Currently, they require a return value of Promise<unknown> | true | undefined:

webextension-polyfill-ts/out/namespaces/runtime.d.ts

Line 583 in 75f8b24

) => Promise<unknown> | true | undefined

Commit where change was made: 85437fc

I believe the correct type should be void rather than undefined so that listeners can return without having to specify undefined.

[Lusito]

The people at DefinitelyTyped are a bit hard on disabling their linting rules globally, so this was the easy fix.

Can you show me an example where this is an issue for you? I don't believe you need to specify undefined for it to work.

[Lusito]

For reference, this is where the discussion at DT happened: DefinitelyTyped/DefinitelyTyped#69704
And this is the issue from the linting rule, still in discussion: typescript-eslint/typescript-eslint#5752

So there are 3 ways to solve this:

1. convince DT maintainers to allow a global disable of the rule.
2. rewrite the generator code, so that it adds a rule-disable comment per line (won't be easy)
3. convince the maintainers of typescript-eslint to make this case allowed in their rule and wait for DT to update their dependency on it.

[namukang]

Sure, here's an example:

Here's a minimal message listener that logs all received messages:

browser.runtime.onMessage.addListener((message) => {
  console.log(message);
});

With the updated type definition for runtime.onMessage.addListener, the above results in the following type error:

Argument of type '(message: unknown) => void' is not assignable to parameter of type '(message: unknown, sender: MessageSender, sendResponse: (message: unknown) => void) => true | Promise<unknown> | undefined'.
  Type 'void' is not assignable to type 'true | Promise<unknown> | undefined'.ts(2345)

As a result, the message listener needs to include an extra return undefined to resolve it:

browser.runtime.onMessage.addListener((message) => {
  console.log(message);
  return undefined;
});

I was hoping that reverting the type definition would be a quick fix, but given the issues you referenced above, I understand the decision you made and agree that it seems like a lot of effort given the upstream challenges.

Thanks for following up with me and sharing the context behind it! (Also, as someone who loves type-safety and has been using this library since it was webextension-polyfill-ts, thank you so much for all your work and effort! <3)

[Lusito]

I might have found a solution, that even improves types to only allow sendResponse with return true. Let's see if this gets approved: DefinitelyTyped/DefinitelyTyped#72037