Add optionality to mapped type substitutions based on existence of an optional modifiers prop #57493
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… optional modifiers prop
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added
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| @@ -18514,10 +18514,20 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| return !!(getUnionType([intersectTypes(type1, type2), neverType]).flags & TypeFlags.Never); | |||
| } | |||
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| function hasOptionalModifiersProperty(mappedType: MappedType) { | |||
| const modifiersType = getApparentType(getModifiersTypeFromMappedType(mappedType)); | |||
| if (!(modifiersType.flags & TypeFlags.Object)) { | |||
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TODO: might also have to handle intersection (that's what isWeakType is doing) and I need to recheck behavior with unions
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recheck behavior with union types later
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@Mateusnasciment Please try to keep comments actionable and on-topic
| @@ -205,6 +206,9 @@ keyofAndIndexedAccess2.ts(108,5): error TS2322: Type '123' is not assignable to | |||
| type StrictExtract<T, U> = T extends U ? U extends T ? T : never : never; | |||
| type StrictExclude<T, U> = T extends StrictExtract<T, U> ? never : T; | |||
| type A<T> = { [Q in { [P in keyof T]: P; }[keyof T]]: T[Q]; }; | |||
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I'm not sure what's the best strategy to avoid circularity here. I didn't look into it yet. I'm hitting the 🛌 but maybe somebody would chime in with some suggestions in the meantime ;p
| function substituteIndexedMappedType(objectType: MappedType, index: Type) { | ||
| const mapper = createTypeMapper([getTypeParameterFromMappedType(objectType)], [index]); | ||
| const templateMapper = combineTypeMappers(objectType.mapper, mapper); | ||
| return instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper); | ||
| const type = instantiateType(getTemplateTypeFromMappedType(objectType.target as MappedType || objectType), templateMapper); | ||
| return addOptionality(type, /*isProperty*/ true, hasOptionalModifiersProperty(objectType)); |
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TODO: this should get the list of known optional properties and check if index is assignable to that, if the substitution happens using a known non-optional property then the optionality shouldn't be added
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I have what I think it the right fix in #57549. The main difference is that my PR is based on computing combined modifier flags, which I think is a better approach. It avoids resolving the members, which may cause circularities as you've observed. Also, member resolution is based on what members are known to be present, not which members might be present. |
fixes #57487