[pickers] DateBuilderReturnType provides wrong type with no arg

[alexey-kozlenkov]

Steps to reproduce

Add this test case to test/utils/pickers/describeGregorianAdapter/testCalculations.ts:

  describe('Method: date', () => {
    //...

    it('should work without args', () => {
      const date = adapter.date().valueOf()

      expect(Math.abs(date - Date.now())).to.be.lessThan(5)
    })
  })

Current behavior

adapter.date() return type is Date | null

Expected behavior

adapter.date() return type should be just Date - same if undefined passed explicitly adapter.date(undefined)

Context

This might be happening because of Distributive conditional types and has an easy fix in types packages/x-date-pickers/src/models/adapters.ts:

-export type DateBuilderReturnType<T extends string | null | undefined, TDate> = T extends null
+export type DateBuilderReturnType<T extends string | null | undefined, TDate> = [T] extends [null]
   ? null
   : TDate;

Your environment

npx @mui/envinfo

  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.

Search keywords: DateBuilderReturnType mui-x-date-pickers

[michelengelen]

Hey @alexey-kozlenkov
Looks like a good fix.
Would you mind opening a PR for this?

[alexey-kozlenkov]

@michelengelen sure, let me try to do that

[github-actions]

⚠️ This issue has been closed. If you have a similar problem but not exactly the same, please open a new issue.
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