feat: adds has module

[ahrjarrett]

changelog

new module: has

• has.oneProperty

  • has.oneProperty lets you express the type of an object that contains exactly 1 property.

  For example:

  /** 
   * @example
   *  const one = singleton({ a: 1 })       // ✅
   * 
   *  const zero = singleton({})            // 🚫
   *  //    ^? const zero: never
   * 
   *  const two = singleton({ a: 1, b: 2 }) // 🚫
   *  //    ^? const two: never
   */
  declare function singleton<const T extends has.oneProperty<T>>(
    objectWithExactlyOneProperty: T
  ): T

• has.oneProperty.debug

  • has.oneProperty.debug is like has.oneProperty, but raises a TypeError if T has 0 or 2+ properties

• has.oneElement

  • has.oneElement lets you express the type of an tuple that contains exactly 1 property.

  For example:

  /** 
   * @example
   *  const one = singleton([1])    // ✅
   *  //    ^? const one: readonly [1]
   * 
   *  const zero = singleton([])    // 🚫
   *  //    ^? const zero: never
   *  const two = singleton([1, 2]) // 🚫
   *  //    ^? const two: never
   */
  declare function oneNumber<const T extends has.oneElement<T, number>>(
    tupleContainingOneNumber: T
  ): T

• has.oneElement.debug

  • has.oneElement.debug is like has.oneElement, but raises a TypeError if T has 0 or 2+ elements

Notes

• Both has.oneProperty and has.oneElement both accept 2 additional optional type parameters:
  1. an invariant param, which allows you to apply an additional constraint on the type of the property itself; and
  2. a debug flag, which, if non-never, changes the behavior of has.one* to raise a TypeError if T fails to satisfy the constraint

[changeset-bot]

🦋 Changeset detected

Latest commit: 0dbbab0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
any-ts	Minor

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