737506e79c
Currently we read lifecycle hooks eagerly during `ɵɵdefineComponent`.
The result is that it is not possible to do any sort of meta-programing
such as mixins or adding lifecycle hooks using custom decorators since
any such code executes after `ɵɵdefineComponent` has extracted the
lifecycle hooks from the prototype. Additionally the behavior is
inconsistent between AOT and JIT mode. In JIT mode overriding lifecycle
hooks is possible because the whole `ɵɵdefineComponent` is placed in
getter which is executed lazily. This is because JIT mode must compile a
template which can be specified as `templateURL` and those we are
waiting for its resolution.
- `+` `ɵɵdefineComponent` becomes smaller as it no longer needs to copy
lifecycle hooks from prototype to `ComponentDef`
- `-` `ɵɵNgOnChangesFeature` feature is now always included with the
codebase as it is no longer tree shakable.
Previously we have read lifecycle hooks from prototype in the
`ɵɵdefineComponent` so that lifecycle hook access would be monomorphic.
This decision was made before we had `T*` data structures. By not
reading the lifecycle hooks we are moving the megamorhic read form
`ɵɵdefineComponent` to instructions. However, the reads happen on
`firstTemplatePass` only and are subsequently cached in the `T*` data
structures. The result is that the overall performance should be same
(or slightly better as the intermediate `ComponentDef` has been
removed.)
- [ ] Remove `ɵɵNgOnChangesFeature` from compiler. (It will no longer
be a feature.)
- [ ] Discuss the future of `Features` as they hinder meta-programing.
Fix #30497
PR Close #35464
Bundle
js_expected_symbol_test
This folder contains tests which assert that most of the code is tree shaken away. This is asserted by keeping gold files of all symbols which are expected to be retained. When doing renaming it is often necessary to update the gold files, to do so use these commands:
yarn bazel run --config=ivy //packages/core/test/bundling/cyclic_import:symbol_test.accept
yarn bazel run --config=ivy //packages/core/test/bundling/hello_world:symbol_test.accept
yarn bazel run --config=ivy //packages/core/test/bundling/injection:symbol_test.accept
yarn bazel run --config=ivy //packages/core/test/bundling/todo:symbol_test.accept