angular-cn/packages/compiler-cli/test/ngtsc/fake_core
Alex Rickabaugh bb290cefae fix(core): make QueryList implement Iterable in the type system (#33536)
Originally, QueryList implemented Iterable and provided a Symbol.iterator
on its prototype. This caused issues with tree-shaking, so QueryList was
refactored and the Symbol.iterator added in its constructor instead. As
part of this change, QueryList no longer implemented Iterable directly.

Unfortunately, this meant that QueryList was no longer assignable to
Iterable or, consequently, NgIterable. NgIterable is used for NgFor's input,
so this meant that QueryList was not usable (in a type sense) for NgFor
iteration. View Engine's template type checking would not catch this, but
Ivy's did.

As a fix, this commit adds the declaration (but not the implementation) of
the Symbol.iterator function back to QueryList. This has no runtime effect,
so it doesn't affect tree-shaking of QueryList, but it ensures that
QueryList is assignable to NgIterable and thus usable with NgFor.

Fixes #29842

PR Close #33536
2019-11-19 13:43:53 -08:00
..
BUILD.bazel build: convert entry_point to label (#30627) 2019-06-11 00:03:11 +00:00
README.md
index.ts fix(core): make QueryList implement Iterable in the type system (#33536) 2019-11-19 13:43:53 -08:00
package.json

README.md

fake_core is a library designed to expose some of the same symbols as @angular/core, without requiring compilation of the whole of @angular/core. This enables unit tests for the compiler to be written without incurring long rebuilds for every change.

  • @angular/core is compiled with @angular/compiler-cli, and therefore has an implicit dependency on it. Therefore core must be rebuilt if the compiler changes.
  • Tests for the compiler which intend to build code that depends on @angular/core must have a data dependency on @angular/core. Therefore core must be built to run the compiler tests, and thus rebuilt if the compiler changes.

This rebuild cycle is expensive and slow. fake_core avoids this by exposing a subset of the @angular/core API, which enables applications to be built by the ngtsc compiler without needing a full version of core present at compile time.