**Description:**
Helper methods were exporting twice, `_` and it's own function name.
We can map the build script to export `_` as it's own name (filename).
Therefore we export only once as `_`, and map the name on the build
script.
```js
// helpers/_foo.js
function _foo() {
// ...
}
export { _foo as _ }
```
```js
// index.js
// We know the func name will be `_foo` based on the filename.
export { _ as _foo } from '_foo.js'
```
Closes#9203
---------
Co-authored-by: magic-akari <akari.ccino@gmail.com>
**Description:**
Fixes stray export in `_using_ctx.js` inside of `packages/helpers`. This was causing build failures in my project, and I believe it was an errant export from a previous version of the helpers package.
**Description:**
At some point the spec text of ES decorators was changed to also have
addInitializer for field decorators. This is already used e.g. in mobx.
This simple change removes the special case that was present for field
decorators and seems to fix the issue for me.
This change is backwards compatible since it only affects code that was
broken before.
**Related issue:**
- Closes#8525
**Description:**
This PR implements the [decorator
metadata](https://github.com/tc39/proposal-decorator-metadata) proposal,
that is now at Stage 3.
As the decorator metadata proposal is a small extension of the decorator
proposal and is not possible to compile the metadata without transpiling
decorators, I opted to implement it into the existing decorator
transformer (and helper)
**Related issue:**
- Closes#7957
