microsoft / microsoft/tsdoc

RFC: @errorCode to provide context for errors for properties

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Dominant language
TypeScript
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Description

It would be nice to be able to inform users when they encounter specific errors related to a property.

In this example use case, we would like to inform the user that a property on a discriminated union can only be set when the discriminator matches the type.

interface Base {
  discriminator: boolean;
  foo: string | never;
}

interface UnionTypeA extends Base {
  discriminator: true;
  foo: string;
}

interface UnionTypeB extends Base {
  discriminator: false;

  /**
   *
   * {@errorCode 2322 | This property can only be set when discriminator is equal to `true`}
   *
   */
  foo: never;
}

type DiscriminatedUnion = UnionTypeA | UnionTypeB;

const bar: DiscriminatedUnion = {
  discriminator: false,
  foo: ""
}

The current error is shown as:
Screenshot 2024-08-23 at 11 35 35 AM

I based the syntax around what I have seen as prior art in the @link tag.

Apologies if this has been suggested or discussed before, I could not find anything from an initial search of issues.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reviewing the existing @link tag behavior and the proposed TypeScript discriminated-union example. Determine how an @errorCode tag should represent property-related diagnostics and what specification changes are needed; done means the syntax and expected error-context behavior are defined clearly enough for implementation.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
documentation
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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