Repository navigation
Applying a constrained generic with type parameters as the argument type doesn't properly catch constrained fields #52309
Description
Bug Report
🔎 Search Terms
generic constraints, generic types, multiple generics, generic type variable, type parameters
🕗 Version & Regression Information
This is the behavior in every version I tried, and I reviewed the FAQ for entries about generics.
⏯ Playground Link
Playground link with relevant code
💻 Code
type PropertiesType = {[key:string]: any};
type RequiredPropertiesType<Props extends PropertiesType> = (Exclude<keyof Props, symbol>)[];
interface JSONSchemaObjectType<
Props extends PropertiesType,
RequiredProps extends RequiredPropertiesType<Props>
> {
properties: Props;
required?: RequiredProps;
additionalProperties?: boolean;
}
const DefineObject = <
Props extends PropertiesType,
RequiredProps extends RequiredPropertiesType<Props>,
Def extends JSONSchemaObjectType<Props, RequiredProps>
>(definition: Def) => {
// noop
}
DefineObject({
properties: {
test: "hi"
},
required: ["test", "broken like me"] // <-- no static type error
})🙁 Actual behavior
The required array accepts values that are not keys used in it's sibling properties
🙂 Expected behavior
The required array is constrained to the keys used in it's sibling properties
Activity
whzx5byb commentedon Jan 20, 2023
You should explicitly provide the constraint as a context to help infer the correct type of
Props:shapirone commentedon Jan 20, 2023
whzx5byb this constrains the argument but causes any conditional typing that relies on
definitionbeing a generic to failRyanCavanaugh commentedon Jan 26, 2023
Can you go into more detail? The above solution is effectively correct; there's not a way to exclude candidates from inference like you would need in order to make this to work.
RyanCavanaugh commentedon Feb 2, 2023
Treating as duplicate of #14829
shapirone commentedon Feb 2, 2023
Sorry for the silence here, I've been looking into the resulting conditional typing failure and haven't been able to reproduce what we're seeing in a simplified TS Playground. Applying the recommended solution appropriately applied the constraint on the
requiredfield, but caused static type test failures that I assumed were related to inference from our conditional typing.I've since realized that the test failures we're seeing are resolved if we assign the result of
DefineObjectto a variable and reference that variable in the surrounding function call, rather than usingDefineObjectdirectly as the object value. Code sample below to illustrateI'm still working on providing a Playground example, but please let me know if this behavior is familiar to you, if I should close this issue and open a new issue when I have more details, or if a pointer to where this creates problems in our actual code base would be helpful 🙇
typescript-bot commentedon Feb 4, 2023
This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.