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Apply uncalled function checks to ternaries #36048
Description
Search Terms
ts2774 ternary condition error function called uncalled
Suggestion
TS2774 (implemented in #32802), i.e. the "This condition will always return true since the function is always defined. Did you mean to call it instead?" error, provides a helpful hint for developers referencing a function in an if statement without calling it. However, the same check doesn't apply to ternaries, which is missing an opportunity to save some debug time and counterintuitive for devs who know about TS2774. I propose reusing TS2774 for developers who forget to call a function in a ternary.
Examples
Now:
const isString = (value: unknown) => typeof value === "string"
// Error (TS2774)
if (isString) {
}
// No error
isString ? true : falseIf this suggestion is adopted:
const isString = (value: unknown) => typeof value === "string"
// Error (TS2774)
if (isString) {
}
// Error(TS2774)
isString ? true : falseChecklist
My suggestion meets these guidelines:
- [✔️] This wouldn't be a breaking change in existing TypeScript/JavaScript code
- [✔️] This wouldn't change the runtime behavior of existing JavaScript code
- [✔️] This could be implemented without emitting different JS based on the types of the expressions
- [✔️] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
- [✔️] This feature would agree with the rest of TypeScript's Design Goals.
Activity
RyanCavanaugh commentedon Jan 7, 2020
Seems reasonable; we'd have to assess for breakage but I suspect this would turn out well
dragomirtitian commentedon Jan 21, 2020
Ryan Cavanaugh (@RyanCavanaugh) Are you taking PRs on this one?
[-]Apply TS2774 to ternaries[/-][+]Apply uncalled function checks to ternaries[/+]DanielRosenwasser commentedon Jan 21, 2020
Yes
DanielRosenwasser commentedon Jan 28, 2020
Just assigning Nathan Shively-Sanders (@sandersn) so that we can follow up on the PR for 3.9 sooner rather than later.
DanielRosenwasser commentedon Feb 20, 2020
Thanks Oleksandr Tarasiuk (@a-tarasyuk)!