Commits on Dec 1, 2022

1. fix(@angular-devkit/build-angular): downlevel class properties when t… …

   …argeting Safari <=v15
   
   The Angular compiler is dependent on static fields being attached to
   user-defined classes. e.g. `static ecmp = defineComponent`.
   
   These static fields sometimes rely on variables from outside of the
   class. e.g. the Angular compiler generates constants for content
   projection that are then accessed in the static field initializer.
   
   Surprisingly such access to these variables may break in Safari <=v15
   when a page is loaded without devtools open. The bug (already solved in
   v16 of Safari)- is very subtle, hard to re-reproduce but basically
   variable scope tracking is broken. This bug is triggered by additional
   parenthesis in the initializer expression. See:
   https://bugs.webkit.org/show_bug.cgi?id=236843.
   
   The TypeScript compiler may generate such additional parenthesis when
   it tries to adjust the `this` context when invoking methods, such as for
   defining animations in the `ecmp` definition.
   
   More details can be found here:
   angular#24355 (comment)
   
   To ensure Angular applications are not subject to this bug when
   targeting Safari <=v15. v15 Safari, both for iOS and Mac is still part of
   the default CLI browserslist with `last 2 Safari majors` (at time of
   writing).
   
   Note that it is important that the Babel plugin properly handles the
   downleveling of static block-defined members. TypeScript will transform
   static fields, like `static ecmp` into `static { this.ecmp = X }` when
   `useDefineForClassFields = false` (which is the case for CLI apps). The
   class properties plugin from Babel seems to handle this in an acceptable
   way. Unlike actual static fields, Babel will not use helpers like
   `defineProperty` for such extracted static blocks though. e.g.
   
   See repro: https://gist.github.com/devversion/dec0dea26e348c509921bf62079b60be
   
   ```js
   class Test {
     x = true;
   
     static b = true;
     static {
       this.a = true;
     }
   }
   
   // into
   
   class X {
     constructor() {
       _defineProperty(this, "x", true);
     }
   }
   _defineProperty(X, "b", true);
   X.a = true;
   ```
   
   note that in practice TypeScript with `useDefineForClassFields = false`
   will put non-static members into the constructor as normal assignments
   regardless- so there would be no change by the Babel plugin.
   
   Fixes angular#24355.

   

   devversion committed Dec 1, 2022
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