refactor: improve inferred types for selector subscriptions #5096
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currently if you do not provide explicit type in the selector, then the handler function will have `unknown` params. This is because TS does not know which generic type to use for `SelectorReturnValue`. I tried using the `NoInfer` type to prevent the handler function from winning the inference, but unfortunately `NoInfer` does not work with return values. The other option was to switch the handler fn and selector fn around, however this is a destructive change. By making the handler fn use its own generics (which are constrained by the original `SelectorReturnValue`), we effectively defer or ensure that the handler doesn't win the inference.
Prithpal-Sooriya
changed the title
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Welp, NVM this fails. It works in the typescript playground (looking at types). But then it breaks when trying to use it lol |
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This is something that's bothered me for a while, so I appreciate you trying to figure it out at least! |
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Agreed, thanks! That |
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Explanation
This was a low hanging fruit to investigate the subscription selector/handler inference (for fun during Quality Quest).
Currently if you do not provide explicit type in the selector, then the handler function will have
unknownparams. This is because TS does not know which which function (handler or selector) to assign the generic typeSelectorReturnValue.Here is a TypeScript Playground with a simplified example.
Playground Link
References
Changelog
@metamask/base-controllerSelectorEventHandlerto use a deferred version ofSelectorReturnValue, so that TS will pick up and use the selectors return value as the Generic.Checklist