ConditionalPickDeep: Fix returning {} instead of never when no keys match#1360
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sindresorhus merged 3 commits intosindresorhus:mainfrom Feb 14, 2026
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sindresorhus
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Feb 9, 2026
som-sm
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Feb 12, 2026
source/conditional-pick-deep.d.ts
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| type _NeverIfEmpty<Type> = [keyof Type] extends [never] ? never : Type; |
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This is incorrect, because keyof Type would be never even for unions with no common properties. For example, ConditionalPickDeep<{a: string} | {b: string}>, string> should return {a: string} | {b: string}, but with this change it returns never.
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| type _NeverIfEmpty<Type> = [keyof Type] extends [never] ? never : Type; | |
| type _NeverIfEmpty<Type> = Type extends EmptyObject ? never : Type; |
The above is better because it lets Type distribute, and EmptyObject is preferable to keyof Type since EmptyObject is already used to achieve the same behavior in nested cases.
type-fest/source/conditional-pick-deep.d.ts
Line 118 in 3995003
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Good catch, fixed. Also added a test for the union case with no common properties.
som-sm
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Feb 14, 2026
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Fixes #1358
Summary
Conditionat any depth,ConditionalPickDeeppreviously returned{}(empty object type). This allowed any properties to be assigned without type errors._NeverIfEmptyhelper that checks if the result has no keys and returnsneverin that case. This is applied only at the top level to avoid interfering with the internal recursiveEmptyObjectexclusion logic.Note
This is the deep variant of the same issue fixed in #1359 for
ConditionalPick.