feat(@jest/types): infer argument types passed to test and describe functions from each tables
#12885
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| <T extends readonly [unknown, ...Array<unknown>]>(table: ReadonlyArray<T>): ( |
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An array of arrays is actually treated as array of tuples. Spreading ['abc', 123] as tuple gives a type a: string, b: number, spreading the same thing as an array results in a type a: string | number, b: string | number. The hard part was to capture indefinite number of tuple members. [unknown, ...Array<unknown>] looks clumsy, but does this job well.
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If a table is defined a variable (not inline), TypeScript treats it as Array<Array<...>>. This overload will catch this case.
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Finally this is here to allow typing template string literals through generic argument.
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Summary
This PR is filling one more gap of types. Currently types of arguments passed from
eachtables totestanddescribefunctions areany. In this field,@types/jestdoes better job. I was playing with for some time. The solutions is different than the one from DT – somewhat better, but with some limitations. Documentation noting the caveats is included (by the way, types from DT has similar issues).Probably I will have to revisit it later, but that is a strong start already.
Test plan
The detailed type tests for
eachnow live in a separate file. The type tests for global API were cleaned up and slightly extended. Could not leave them. Apologies for many tests. Just wanted to be sure that everything works.