reduxjs/reselect v4.1.3

on GitHub

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