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Fix problem with transitive generics in Signatures #613

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Fix problem with transitive generics in Signatures #613

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753390a
Allow generics in Signatures
gossi Aug 17, 2023
f79c9c5
attempt to add failing type tests
gossi Sep 9, 2023
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3 changes: 2 additions & 1 deletion packages/template/-private/signature.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,8 @@ export type ComponentSignatureBlocks<S> = S extends { Blocks: infer Blocks }

/** Given a component signature `S`, get back the `Element` type. */
export type ComponentSignatureElement<S> = S extends { Element: infer Element }
? NonNullable<Element> extends never
? NonNullable<Element> extends never
// ? Element extends null
Comment on lines +48 to +49
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this is a temporary revert. That is to write failing tests, which when switching back to the fix should be resolved.

? unknown
: Element
: unknown;
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54 changes: 54 additions & 0 deletions packages/template/__tests__/signature.test.ts
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Expand Up @@ -4,6 +4,7 @@ import {
ComponentSignatureBlocks,
ComponentSignatureElement,
} from '../-private/signature';
import { ComponentLike } from '../';

type LegacyArgs = {
foo: number;
Expand Down Expand Up @@ -153,3 +154,56 @@ interface FullLongSig {
expectTypeOf<ComponentSignatureArgs<FullLongSig>>().toEqualTypeOf<FullLongSig['Args']>();
expectTypeOf<ComponentSignatureBlocks<FullLongSig>>().toEqualTypeOf<FullLongSig['Blocks']>();
expectTypeOf<ComponentSignatureElement<FullLongSig>>().toEqualTypeOf<FullLongSig['Element']>();

// types to simulate the `(element)` helper
// Issue: https://github.com/typed-ember/glint/issues/610
type ElementFromTagName<T extends string> = T extends keyof HTMLElementTagNameMap
? HTMLElementTagNameMap[T]
: Element;
type ElementHelperPositional<T extends string> = [name: T];
type ElementHelperReturn<T extends string> = ComponentLike<{
Element: ElementFromTagName<T>;
Blocks: { default: [] };
}>;

interface ElementSignature<T extends string> {
Args: {
Positional: ElementHelperPositional<T>;
};
Return: ElementHelperReturn<T> | undefined;
}

// signature for a component receiving an `(element)`
interface ElementReceiverSignature<T extends string> {
Element: ElementFromTagName<T>;
Args: {
element: ElementSignature<T>['Return'];
};
Blocks: {
default: [];
};
}

expectTypeOf<ComponentSignatureArgs<ElementReceiverSignature<'div'>>>().toEqualTypeOf<{
Named: {
element: ElementSignature<'div'>['Return'];
};
Positional: []
}>();

expectTypeOf<ComponentSignatureArgs<ElementReceiverSignature<null>>>().toEqualTypeOf<{
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Actually, this line is the problematic part here, I'd say. For what I think needs to be tested, is how the components are invoked, rather than the static definition?

That is, in invocation, this should be null. But this is obviously a failure:

Type 'null' does not satisfy the constraint 'string'.

To my knowledge, to properly test this, is to provide broken types. How to do that?

Named: {
element: {
Args: {
Positional: ElementHelperPositional<never>;
};
Return: ComponentLike<{
Element: Element;
Blocks: { default: [] };
}> | undefined;
} | undefined;
};
Positional: []
}>();
expectTypeOf<ComponentSignatureElement<ElementReceiverSignature<'div'>>>().toEqualTypeOf<HTMLDivElement>();

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