feat(core): make SimpleChanges generic #64535
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Moves the `SimpleChange` and lifecycle hook interfaces so that they can import other symbols from `core`.
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Currently it's easy to make a mistake when accessing properties on `SimpleChanges`, because the keys aren't typed. These changes add an optional generic to the interface so that users can get a compilation error if they make a typo. A few things to note: 1. The generic argument is optional and we revert to the old behavior if one isn't passed for backwards compatibility. 2. All of the keys are optional, because they aren't guaranteed to be present for any `ngOnChanges` invocation. 3. We unwrap the values of input signals to match the behavior at runtime. Fixes angular#17560.
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Oct 20, 2025
| export type SimpleChanges<T = unknown> = T extends object | ||
| ? { | ||
| [Key in keyof T]?: SimpleChange< | ||
| T[Key] extends {[ɵINPUT_SIGNAL_BRAND_READ_TYPE]: infer V} ? V : T[Key] |
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Do you know we have a helper for this already? (e.g. for type checking?)
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AFAIK we don't, I only found the function that asserts if a type is a writable signal. Initially I wanted to use the public InputSignal type, but it would've gotten complicated since we have some variations like InputSignalWithTransform.
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Passing TGP after some client app cleanups. |
kirjs
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Oct 20, 2025
| expect(ngModel.control.disabled).toEqual(false); | ||
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| ngModel.ngOnChanges({isDisabled: new SimpleChange('', false, false)}); | ||
| ngModel.ngOnChanges({isDisabled: new SimpleChange('' as any, false, false)}); |
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Why do you need to cast those?
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It's because the types for the previous and current value don't match. I think it's testing something that isn't officially supported through types.
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Currently it's easy to make a mistake when accessing properties on `SimpleChanges`, because the keys aren't typed. These changes add an optional generic to the interface so that users can get a compilation error if they make a typo. A few things to note: 1. The generic argument is optional and we revert to the old behavior if one isn't passed for backwards compatibility. 2. All of the keys are optional, because they aren't guaranteed to be present for any `ngOnChanges` invocation. 3. We unwrap the values of input signals to match the behavior at runtime. Fixes #17560. PR Close #64535
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Currently it's easy to make a mistake when accessing properties on
SimpleChanges, because the keys aren't typed. These changes add an optional generic to the interface so that users can get a compilation error if they make a typo.A few things to note:
ngOnChangesinvocation.Fixes #17560.