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Showing content from https://github.com/microsoft/TypeScript/issues/30825 below:

add stricter Omit helper type · Issue #30825 · microsoft/TypeScript · GitHub

omit strict

The new Omit type does not restrict the omitted keys to be keys actually present on the given type. There should be some avenue to express "omit, but only with keys that are present", likely either a change to Omit or some other Omit-like type.

Copied from pelotom/type-zoo#31.

The benefit that a stricter type has is primarily:

• Preventing typos.
• Allowing the compiler to pick up on rename refactors automatically.

Currently, permissive Omit acts as a "barrier" that prevents rename refactors from passing through, which means that any such refactor generates whole bunches of errors that have to be manually fixed. If the field in question is optional, this can actually introduce bugs.

And some further color:

I generally use Omit with string literal unions (as opposed to, say, generic types that extends string), because I often use them for defining higher-order React components that wrap another component except for this one prop. As such, in my use case, I never want a permissive Omit.

interface ImplementationDetailProps {
  publiclyVisibleFoo: Foo;
  filePrivateBar: Bar;
}

class ImplementationDetail extends React.Component<ImplementationDetailProps> { ... }

export type PublicProps = Omit<ImplementationDetailProps, "filePrivateBar">;

export class Public extends React.Component<PublicProps> { ... }

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

sindresorhus, aeruhxi, scttcper, Rowno, BendingBender and 71 moreleoyli, G-Rath, gkalpak, billyjanitsch, gins3000 and 3 more

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