Previously, the angular.io app was broken on IE 11. In particular, pages
that included Custom Elements would fail to load, because the
`Reflect.construct()` method (which the Custom Elements ES5 shim relies
on) was not available.

This commit fixes this by loading the polyfill for `Reflect.construct()`
on browsers that do not support ES2015 (including IE 11).

PR Close #41162

…angular#41162)

The custom elements spec is not compatible with ES5 style classes. This
means ES2015 code compiled to ES5 will not work with a native
implementation of Custom Elements. To support browsers that natively
support Custom Elements but not ES2015 modules, we load
`@webcomponents/custom-elements/src/native-shim.js`, which minimally
augments the native implementation to be compatible with ES5 code.
(See [here][1] for more details.)

Previously, the shim was included in `polyfills.ts`, which meant it was
loaded in all browsers (even those supporting ES2015 modules and thus
not needing the shim).

This commit moves the shim from `polyfills.ts` to a `nomodule` script
tag in `index.html`. This will ensure that it is only loaded in browsers
that do not support ES2015 modules and thus do not needed the shim.

NOTE:
This commit also reduces size of the polyfills bundle by ~400B
(52609B --> 52215B).

[1]: https://www.npmjs.com/package/@webcomponents/custom-elements#es5-vs-es2015

PR Close angular#41162

Previously, the angular.io app was broken on IE 11. In particular, pages
that included Custom Elements would fail to load, because the
`Reflect.construct()` method (which the Custom Elements ES5 shim relies
on) was not available.

This commit fixes this by loading the polyfill for `Reflect.construct()`
on browsers that do not support ES2015 (including IE 11).

PR Close angular#41162

…nts but not ES2015

Before angular#41162, angular.io was broken on IE 11 due to missing a polyfill
for an API (`Reflect.construct()`) needed by the Custom Elements ES5
shim. angular#41162 tried to fix this by loading the necessary polyfill
(`es.reflect.construct.js`) on browsers that do not support ES2015
modules (including IE 11).

It turns out that the fix in angular#41162 was itself broken, because the
`es.reflect.consruct.js` script (included directly in the page via a
`<script>` tag) was in CommonJS format (which cannot run in the browser
as is). By chance, this still allowed browsers that supported neither
Custom Elements nor ES2015 modules (such as IE 11) to work correctly as
a side-effect of loading the `@webcomponents/custom-elements` polyfill
after the Custom Elements ES5 shim (`native-shim.js`). However, on the
few browsers that natively support Custom Elements but not ES2015
modules, angular.io would still be broken.

This commit correctly fixes angular.io on all browsers by properly
bundling the polyfills and transpiling to ES5.

Implementation-wise, we use [esbuild][1] for bundling the polyfills (and
converting from CommonJS to a browser-compatible, IIFE-based format) and
[swc][2] for downleveling the code to ES5 (since `esbuild` only supports
ES2015+).

[1]: https://esbuild.github.io/
[2]: https://swc.rs/

…#41162) (#41184)

The custom elements spec is not compatible with ES5 style classes. This
means ES2015 code compiled to ES5 will not work with a native
implementation of Custom Elements. To support browsers that natively
support Custom Elements but not ES2015 modules, we load
`@webcomponents/custom-elements/src/native-shim.js`, which minimally
augments the native implementation to be compatible with ES5 code.
(See [here][1] for more details.)

Previously, the shim was included in `polyfills.ts`, which meant it was
loaded in all browsers (even those supporting ES2015 modules and thus
not needing the shim).

This commit moves the shim from `polyfills.ts` to a `nomodule` script
tag in `index.html`. This will ensure that it is only loaded in browsers
that do not support ES2015 modules and thus do not needed the shim.

NOTE:
This commit also reduces size of the polyfills bundle by ~400B
(52609B --> 52215B).

[1]: https://www.npmjs.com/package/@webcomponents/custom-elements#es5-vs-es2015

PR Close #41162

PR Close #41184

Previously, the angular.io app was broken on IE 11. In particular, pages
that included Custom Elements would fail to load, because the
`Reflect.construct()` method (which the Custom Elements ES5 shim relies
on) was not available.

This commit fixes this by loading the polyfill for `Reflect.construct()`
on browsers that do not support ES2015 (including IE 11).

PR Close #41162

PR Close #41184

…nts but not ES2015 (#41183)

Before #41162, angular.io was broken on IE 11 due to missing a polyfill
for an API (`Reflect.construct()`) needed by the Custom Elements ES5
shim. #41162 tried to fix this by loading the necessary polyfill
(`es.reflect.construct.js`) on browsers that do not support ES2015
modules (including IE 11).

It turns out that the fix in #41162 was itself broken, because the
`es.reflect.consruct.js` script (included directly in the page via a
`<script>` tag) was in CommonJS format (which cannot run in the browser
as is). By chance, this still allowed browsers that supported neither
Custom Elements nor ES2015 modules (such as IE 11) to work correctly as
a side-effect of loading the `@webcomponents/custom-elements` polyfill
after the Custom Elements ES5 shim (`native-shim.js`). However, on the
few browsers that natively support Custom Elements but not ES2015
modules, angular.io would still be broken.

This commit correctly fixes angular.io on all browsers by properly
bundling the polyfills and transpiling to ES5.

Implementation-wise, we use [esbuild][1] for bundling the polyfills (and
converting from CommonJS to a browser-compatible, IIFE-based format) and
[swc][2] for downleveling the code to ES5 (since `esbuild` only supports
ES2015+).

[1]: https://esbuild.github.io/
[2]: https://swc.rs/

PR Close #41183

…nts but not ES2015 (#41183)

Before #41162, angular.io was broken on IE 11 due to missing a polyfill
for an API (`Reflect.construct()`) needed by the Custom Elements ES5
shim. #41162 tried to fix this by loading the necessary polyfill
(`es.reflect.construct.js`) on browsers that do not support ES2015
modules (including IE 11).

It turns out that the fix in #41162 was itself broken, because the
`es.reflect.consruct.js` script (included directly in the page via a
`<script>` tag) was in CommonJS format (which cannot run in the browser
as is). By chance, this still allowed browsers that supported neither
Custom Elements nor ES2015 modules (such as IE 11) to work correctly as
a side-effect of loading the `@webcomponents/custom-elements` polyfill
after the Custom Elements ES5 shim (`native-shim.js`). However, on the
few browsers that natively support Custom Elements but not ES2015
modules, angular.io would still be broken.

This commit correctly fixes angular.io on all browsers by properly
bundling the polyfills and transpiling to ES5.

Implementation-wise, we use [esbuild][1] for bundling the polyfills (and
converting from CommonJS to a browser-compatible, IIFE-based format) and
[swc][2] for downleveling the code to ES5 (since `esbuild` only supports
ES2015+).

[1]: https://esbuild.github.io/
[2]: https://swc.rs/

PR Close #41183