When compiling libraries, this feature extracts the minimal information
from the directives/pipes/modules of the library into `.ngsummary.json` files,
so that applications that use this library only need to be recompiled
if one of the summary files change, but not on every change
of the libraries (e.g. one of the templates).
Only works if individual codegen for libraries is enabled,
see the `generateCodeForLibraries: false` option.
Closes#12787
## Inheritance Semantics:
Decorators:
1) list the decorators of the class and its parents in the ancestor first order
2) only use the last decorator of each kind (e.g. @Component / ...)
Constructor parameters:
If a class inherits from a parent class and does not declare
a constructor, it inherits the parent class constructor,
and with it the parameter metadata of that parent class.
Lifecycle hooks:
Follow the normal class inheritance model,
i.e. lifecycle hooks of parent classes will be called
even if the method is not overwritten in the child class.
## Example
E.g. the following is a valid use of inheritance and it will
also inherit all metadata:
```
@Directive({selector: 'someDir'})
class ParentDirective {
constructor(someDep: SomeDep) {}
ngOnInit() {}
}
class ChildDirective extends ParentDirective {}
```
Closes#11606Closes#12892
- `NgHost` to `CompilerHost`
- `AotCompilerHost.resolveFileToImport` to `AotCompilerHost.fileNameToModuleName`
- `AotCompilerHoset.resolveImportToFile` to `AotCompilerHost.moduleNameToFileName`
This is needed to resolve symbols without `.d.ts` files.
This bumps the version of the metadata from 1 to 2.
This adds logic into `ng_host.ts` to automatically upgrade
version 1 to version 2 metadata by adding the exported symbols
from the `.d.ts` file.
