This release rewrites the TS type inference of input selector parameters for correctness, fixes inference of createStructuredSelector
inputs, and fixes an issue with the OutputSelectorFields
type not being exported.
Changelog
Input Selector Parameter Inference Improvements
Reselect's types have always been extremely tricky, because it involves passing multiple input selectors with potentially heterogeneous, and then nested function composition of multiple selectors. Additionally, the input selectors can be passed as individual arguments or a single array of input selectors.
The 4.0.0 typedefs dealt with this by hand-writing dozens of overloads, which was absolutely impossible to maintain.
In 4.1, we took advantage of TS's improved abilities to infer array/tuple types to consolidate the typedefs.
One of the issues that happened as a result was that arguments at the same input parameter index were being "unioned" together, rather than "intersectioned". For example, in this complex selector:
const input1 = (
_: StateA,
{ testNumber }: { testNumber: number },
c: number,
d: string
) => testNumber
const input2 = (
_: StateA,
{ testString }: { testString: string },
c: number | string
) => testString
const input3 = (
_: StateA,
{ testBoolean }: { testBoolean: boolean },
c: number | string,
d: string
) => testBoolean
const input4 = (_: StateA, { testString2 }: { testString2: string }) =>
testString2
const testSelector = createSelector(
input1,
input2,
input3,
input4,
(testNumber, testString, testBoolean) => testNumber + testString
)
The second arg should end up as an object like {testNumber: number, testString: string, testBoolean: boolean, testString2: string}
. However, it was ending up as four separate one-field objects. Similarly, the combination of number
and number | string
should be narrowed down to just number
as an acceptable value.
We've rewritten the types to successfully accomplish that (although it took a lot of collective effort and headbanging to actually pull this off!) This should now give much more correct results when determining the final parameters that can be passed to a selector.
createStructuredSelector
Fixes
Similarly, createStructuredSelector
wasn't always inferring its arguments properly. We were able to reuse the parameter inference work here as well.
OutputSelectorFields
Exported
The public OutputSelector
type depended on an internal OutputSelectorFields
type, but since OSF
wasn't being exported, TS would throw errors when trying to generate declaration files that exported selectors. That is now public as well.
What's Changed
- Rewrite function parameter type inference to fix assorted issues by @markerikson in #549
Full Changelog: v4.1.2...v4.1.3