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| # Storing Metadata in `.d.ts` files | ||
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| Previous version of Angular used `metadata.json` files to store information about directives/component/pipes/ng-modules. | ||
| `ngc` compiler would than do a global analysis to generate the `.ngfactory.ts` files from the `metadata.json`. | ||
| Ivy strives for locality, which means that `ngtsc` should not need any global information in order to compile the system. | ||
| The above is mostly true. | ||
| Unfortunately, in order for `ngtsc` to generate code which is tree shakable `ngtsc` does need to have global knowledge. | ||
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| Here is an abbreviated example of breakage of tree-shake-ability. | ||
| ```typescript | ||
| @Directive({ | ||
| selector: '[tooltip]' | ||
| }) | ||
| export class TooltipDirective { | ||
| // ngtsc generates this: | ||
| static ngDirectiveDef = defineDirective(...); | ||
| } | ||
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| @Component({ | ||
| selector: 'my-app', | ||
| template: 'Hello World!' | ||
| }) | ||
| class MyAppComponent { | ||
| // ngtsc generates this: | ||
| static ngDirectiveDef = defineComponent({ | ||
| ... | ||
| directives: [ | ||
| // BREAKS TREE-SHAKING!!! | ||
| // TooltipDirective included here because it was declared in the NgModule | ||
| // ngtsc does not know it can be omitted. | ||
| // Only way for ngtsc to know that it can omit TooltipDirective is if it knows | ||
| // its selector and see if the selector matches the current component's template. | ||
| TooltipDirective | ||
| ] | ||
| }); | ||
| } | ||
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| @NgModule({ | ||
| declarations: [MyAppComponent, TooltipDirective], | ||
| bootstrap: [MyAppComponent], | ||
| }) | ||
| class MyAppModule { | ||
| // ngtsc generates this: | ||
| static ngDirectiveDef = defineNgModule(...); | ||
| } | ||
| ``` | ||
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| Notice that `ngtsc` can't remove `TooltipDirective` because it would need to know its selector and see if the directive matches in the component's template. | ||
| Knowing the selector breaks locality and so we make an exception for some locality information such as selector, inputs and outputs. | ||
| Since we are breaking the locality rule, we need to store the information someplace since `ngtsc` can't have access to the `TooltipDirective` source. | ||
| We store the information in the `.d.ts` file like so. | ||
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| ```typescript | ||
| class TooltipDirective { | ||
| static ngDirectiveDef: DirectiveDefWithMeta<TooltipDirective, '[tooltip]', '', {}, {}, []> | ||
| } | ||
| ``` |
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(keyup.enter)works in the current view engine so we should preserve this functionality, otherwise this is a breaking change.There was a problem hiding this comment.
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Yes, but it is all existing functionality from
Renderer2and so I don't think we need to track it here.