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Remove type and optionality constraints from @continuationToken decorator #9078

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Remove type and optionality constraints from @continuationToken decorator #9078

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Copilot AI commented Nov 24, 2025 •
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The @continuationToken decorator enforced that properties be of type string, preventing nullable types like string | null and rejecting non-string types entirely. This constraint was unnecessarily restrictive for pagination patterns.

Changes

  • packages/compiler/src/lib/paging.ts: Removed validation function from continuationTokenDecorator that enforced string type requirement
  • packages/compiler/test/decorators/paging.test.ts: Added tests covering nullable types, optional properties, and non-string types

Usage

The decorator now accepts any type without validation:

model ListPageInfo {
  @pageItems items: string[];
  
  // Now supported: nullable non-optional
  @continuationToken endCursor: string | null;
  
  // Already worked, still works: optional
  @continuationToken token?: string;
  
  // Now supported: non-string types
  @continuationToken offset: int32;
}

Backward compatible - all existing usage continues to work unchanged.

Original prompt

This section details on the original issue you should resolve

<issue_title>[Bug]: Continuation token must allow nullable non optional fields</issue_title>
<issue_description>### Describe the bug

Currently @continuationToken supports only string type for the field. Like this.

model ListPageInfo {
    startCursor?: string;

    @continuationToken
    endCursor?: string;

    hasNext: boolean;
    hasPrev: boolean;
}

While having optional field is fine, for typescript case, to enforce more consistent typing I prefer to make fields nullable instead, therefore compiler would highlight missing expected nullable field.

Therefore @continuationToken should support more than field optionality way of representing the token which might be or might not be, but the field is always present otherwise.

Reproduction

model ListPageInfo {
    startCursor?: string;

    @continuationToken
    endCursor: string | null;

    hasNext: boolean;
    hasPrev: boolean;
}

decorator gives:
Cannot apply continuationToken decorator to string | null since it is not assignable to stringTypeSpec(decorator-wrong-target)

Checklist

<agent_instructions>Remove the constraint that requires the target property of @continuationToken to be a string and the constraint that requires it to be a required property. Correct any tests and add new tests to verify that an optional property cna be marked with this decorator.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@timotheeguerin This feels resonable, not sure it should even force it to be a string

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Copilot AI changed the title [WIP] Fix continuation token to support nullable fields Remove type and optionality constraints from @continuationToken decorator Nov 24, 2025
Copilot AI requested a review from markcowl November 24, 2025 19:31
Copilot finished work on behalf of markcowl November 24, 2025 19:31
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npm i https://pkg.pr.new/microsoft/typespec/@typespec/compiler@9078

commit: ffa089c

@microsoft-github-policy-service microsoft-github-policy-service bot added the compiler:core Issues for @typespec/compiler label Dec 2, 2025
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github-actions bot commented Dec 2, 2025 •
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All changed packages have been documented.

  • ✅ @typespec/compiler
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@typespec/compiler - feature ✏️

Remove type constraints from @continuationToken decorator

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@markcowl markcowl Awaiting requested review from markcowl markcowl is a code owner

@bterlson bterlson Awaiting requested review from bterlson bterlson will be requested when the pull request is marked ready for review bterlson is a code owner

@timotheeguerin timotheeguerin Awaiting requested review from timotheeguerin timotheeguerin will be requested when the pull request is marked ready for review timotheeguerin is a code owner

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@AlitzelMendez AlitzelMendez Awaiting requested review from AlitzelMendez AlitzelMendez will be requested when the pull request is marked ready for review AlitzelMendez is a code owner

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[Bug]: Continuation token must allow nullable non optional fields

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@markcowl @timotheeguerin