Merge pull request #256 from reactjs/sync-66820686

Sync with reactjs.org @ 6682068

Author: taehwanno

content/blog/2016-07-11-introducing-reacts-error-code-system.md

@@ -9,7 +9,7 @@ Prior to this release, we stripped out error messages at build-time and this is
 
 > Minified exception occurred; use the non-minified dev environment for the full error message and additional helpful warnings.
 
-In order to make debugging in production easier, we're introducing an Error Code System in [15.2.0](https://github.com/facebook/react/releases/tag/v15.2.0). We developed a [gulp script](https://github.com/facebook/react/blob/master/scripts/error-codes/gulp-extract-errors.js) that collects all of our `invariant` error messages and folds them to a [JSON file](https://github.com/facebook/react/blob/master/scripts/error-codes/codes.json), and at build-time Babel uses the JSON to [rewrite](https://github.com/facebook/react/blob/master/scripts/error-codes/replace-invariant-error-codes.js) our `invariant` calls in production to reference the corresponding error IDs. Now when things go wrong in production, the error that React throws will contain a URL with an error ID and relevant information. The URL will point you to a page in our documentation where the original error message gets reassembled.
+In order to make debugging in production easier, we're introducing an Error Code System in [15.2.0](https://github.com/facebook/react/releases/tag/v15.2.0). We developed a [script](https://github.com/facebook/react/blob/master/scripts/error-codes/extract-errors.js) that collects all of our `invariant` error messages and folds them to a [JSON file](https://github.com/facebook/react/blob/master/scripts/error-codes/codes.json), and at build-time Babel uses the JSON to [rewrite](https://github.com/facebook/react/blob/master/scripts/error-codes/transform-error-messages.js) our `invariant` calls in production to reference the corresponding error IDs. Now when things go wrong in production, the error that React throws will contain a URL with an error ID and relevant information. The URL will point you to a page in our documentation where the original error message gets reassembled.
 
 While we hope you don't see errors often, you can see how it works [here](/docs/error-decoder.html?invariant=109&args[]=Foo). This is what the same error from above will look like:
 

content/blog/2020-09-22-introducing-the-new-jsx-transform.md

@@ -20,7 +20,7 @@ Upgrading to the new transform is completely optional, but it has a few benefits
 **This upgrade will not change the JSX syntax and is not required.** The old JSX transform will keep working as usual, and there are no plans to remove the support for it.
 
 
-[React 17 RC](/blog/2020/08/10/react-v17-rc.html) already includes support for the new transform, so go give it a try! To make it easier to adopt, after React 17 is released, we also plan to backport its support to React 16.x, React 15.x, and React 0.14.x. You can find the upgrade instructions for different tools [below](#how-to-upgrade-to-the-new-jsx-transform).
+[React 17 RC](/blog/2020/08/10/react-v17-rc.html) already includes support for the new transform, so go give it a try! To make it easier to adopt, **we've also backported its support** to React 16.14.0, React 15.7.0, and React 0.14.10. You can find the upgrade instructions for different tools [below](#how-to-upgrade-to-the-new-jsx-transform).
 
 Now let's take a closer look at the differences between the old and the new transform.
 
@@ -92,7 +92,7 @@ If you aren't ready to upgrade to the new JSX transform or if you are using JSX
 
 If you want to upgrade, you will need two things:
 
-* **A version of React that supports the new transform** (currently, only [React 17 RC](/blog/2020/08/10/react-v17-rc.html) supports it, but after React 17.0 has been released, we plan to make additional compatible releases for 0.14.x, 15.x, and 16.x).
+* **A version of React that supports the new transform** ([React 17 RC](/blog/2020/08/10/react-v17-rc.html) and higher supports it, but we've also released React 16.14.0, React 15.7.0, and React 0.14.10 for people who are still on the older major versions).
 * **A compatible compiler** (see instructions for different tools below).
 
 Since the new JSX transform doesn't require React to be in scope, [we've also prepared an automated script](#removing-unused-react-imports) that will remove the unnecessary imports from your codebase.
@@ -111,7 +111,7 @@ Gatsby [v2.24.5](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby/
 
 >Note
 >
->If you get [this Gatsby error](https://github.com/gatsbyjs/gatsby/issues/26979) after upgrading to React `17.0.0-rc.2`, run `npm update` to fix it.
+>If you get [this Gatsby error](https://github.com/gatsbyjs/gatsby/issues/26979) after upgrading to React 17 RC, run `npm update` to fix it.
 
 ### Manual Babel Setup {#manual-babel-setup}
 
@@ -172,6 +172,8 @@ Starting from Babel 8, `"automatic"` will be the default runtime for both plugin
 > Note
 >
 > If you use JSX with a library other than React, you can use [the `importSource` option](https://babeljs.io/docs/en/babel-preset-react#importsource) to import from that library instead -- as long as it provides the necessary entry points. Alternatively, you can keep using the classic transform which will continue to be supported.
+>
+> If you're a library author and you are implementing the `/jsx-runtime` entry point for your library, keep in mind that [there is a case](https://github.com/facebook/react/issues/20031#issuecomment-710346866) in which even the new transform has to fall back to `createElement` for backwards compatibility. In that case, it will auto-import `createElement` directly from the *root* entry point specified by `importSource`.
 
 ### ESLint {#eslint}