Add JSX.ElementChildrenAttribute change to TypeScript 5.8 release notes

[nmattia]

🔎 Search Terms

tsx, jsx, children, 5.8

🕗 Version & Regression Information

• This changed between versions 5.7.3 and 5.8
• This changed in commit or PR 60880

⏯ Playground Link

No response

💻 Code

declare global {
  namespace JSX {
    type Element = HTMLElement; /* return type for 'jsx()' */

    /* accepted element tags & attributes */
    type IntrinsicElements = {
      /* All HTML elements */
      [Tag in keyof HTMLElementTagNameMap]: {
        [T in HTMLElementStringAttributes<Tag>]?: string | Dyn<string>;
      } & {
        [T in HTMLElementNumberAttributes<Tag>]?: number | Dyn<number>;
      } & (Tag extends keyof TwrlOverrides ? TwrlOverrides[Tag] : {}) & {
          style?: string /* note: This should probably be CSSStyleDeclaration */;
          // BREAKS HERE without this: children?: Children /* defines the type of children */;
        };
    };
  }
}

🙁 Actual behavior

The breaking change is not listed in the 5.8 Release Notes

🙂 Expected behavior

The breaking change should be listed in the 5.8 Release Notes

Additional information about the issue

I ran into issues when upgrading TypeScript and narrowed it down to 5.7.3 to 5.8. The issues is that children is not inferred by default.

Luckily I came across this discussion: #61354

This led me to this PR: #60880

It would have been much faster if the (breaking) change had been mentioned in the 5.8 release notes. Moreover, one (apparent?) side effect of #61354 is that children does not have a default anymore (i.e. if JSX.ElementChildrenAttribute is not set, pre-5.8 children would be accepted; post-5.8 not anymore).

Here's the JSX implementation that surfaced the issue for me:

declare global {
  namespace JSX {
    type Element = HTMLElement; /* return type for 'jsx()' */

    /* accepted element tags & attributes */
    type IntrinsicElements = {
      /* All HTML elements */
      [Tag in keyof HTMLElementTagNameMap]: {
        [T in HTMLElementStringAttributes<Tag>]?: string | Dyn<string>;
      } & {
        [T in HTMLElementNumberAttributes<Tag>]?: number | Dyn<number>;
      } & (Tag extends keyof TwrlOverrides ? TwrlOverrides[Tag] : {}) & {
          style?: string /* note: This should probably be CSSStyleDeclaration */;
          children?: Children /* defines the type of children */; // <- this is now REQUIRED
        };
    };
  }
}

Fix: nmattia/twrl@d83fde4#diff-8e3158c55134a198f9c40ac714ce358df04312a9ca77d7726e1813fb2ba5b5c0R34