# Issue

The cache updates are performed in a wrong way, resulting in a duplicate collection:

**Error:**

```log
webpack-internal:///./node_modules/react-dom/cjs/react-dom.development.js:88 Warning: Encountered two children with the same key, `6f3f7265-0d97-4708-a3ea-7dee76dc0a0a`. Keys should be unique so that components maintain their identity across updates. Non-unique keys may cause children to be duplicated and/or omitted — the behavior is unsupported and could change in a future version.
```

**Video:**

![broken](https://user-images.githubusercontent.com/1265681/95336501-0c170180-08b1-11eb-9273-6ac9e37ceb41.gif)

# Fix

**Video:**

![fixed](https://user-images.githubusercontent.com/1265681/95336538-15a06980-08b1-11eb-8d5e-6acc07e16138.gif)

This adds the initial changes outlined in the [i18n routing RFC](https://github.com/vercel/next.js/discussions/17078). This currently treats the locale prefix on routes similar to how the basePath is treated in that the config doesn't require any changes to your pages directory and is automatically stripped/added based on the detected locale that should be used. 

Currently redirecting occurs on the `/` route if a locale is detected regardless of if an optional catch-all route would match the `/` route or not we may want to investigate whether we want to disable this redirection automatically if an `/index.js` file isn't present at root of the pages directory. 

TODO: 

- [x] ensure locale detection/populating works in serverless mode correctly
- [x] add tests for locale handling in different modes, fallback/getStaticProps/getServerSideProps

To be continued in fall-up PRs

- [ ] add tests for revalidate, auto-export, basePath + i18n
- [ ] add mapping of domains with locales
- [ ] investigate detecting locale against non-index routes and populating the locale in a cookie

x-ref: https://github.com/vercel/next.js/issues/17110

Fixes #17200

Addresses remaining comments from https://github.com/vercel/next.js/pull/17491.

Addresses https://github.com/vercel/next.js/issues/17453.

Follow-up to https://github.com/vercel/next.js/pull/17538 per https://github.com/vercel/next.js/pull/17538#discussion_r499647323 this updates the check to use the existing `hasNextSupport` export instead of checking the environment variable directly

Added a test case to make sure that creating a new project within the current directory works as expected.

Follow-up to https://github.com/vercel/next.js/pull/17533 this makes sure the file used to signal release stats should be skipped for a non-release merge is created in a location that is accessible by the stats action and also updates the release action info detection for the new workflow

This makes sure to normalize the params for optional catch-all routes on Vercel since for `fallback: true` pages the `[[...paramName]]` value will be provided for the undefined/root param which needs to be normalized. 

Tests have been added in https://github.com/vercel/vercel/pull/5247 and were manually tested with the changes in this PR with https://github.com/ijjk/next-update-loader

Fixes: https://github.com/vercel/next.js/issues/17220
x-ref: https://github.com/vercel/vercel/pull/5247

This adds a warning when `next export` and custom routes are defined  outside of a platform that supports them since they won't be applied anymore. 

Fixes #16431
* Added `.babelrc` with `next/babel` to remove the need of the React import on the `with-storybook` example. 

Noticed this method was left-over from previous query handling logic in `api-utils` while working on https://github.com/vercel/next.js/pull/17370 so this removes the extra code which should be safe since `api-utils` is an internal file that shouldn't be relied on externally. 

The page describing exportPathMap goes straight into an example without explaining what the config is for.

Co-authored-by: Nkodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

This adds a note about public files and pages taking higher priority over rewrites causing them to not be able to be rewritten unless the files are renamed first since this has been asked a few times. 

x-ref: https://github.com/vercel/next.js/discussions/17513
x-ref: https://github.com/vercel/next.js/discussions/9081#discussioncomment-22077
x-ref: https://github.com/vercel/next.js/discussions/9081#discussioncomment-21995

Fixes https://github.com/vercel/next.js/issues/17505

If this component is missing, an error will be printed to the console

```
Expected Document Component Head was not rendered. Make sure you render them in your custom `_document`
See more info here https://err.sh/next.js/missing-document-component
```

Additionally, any components which use CSS modules will fail with an error.

This is documented in https://nextjs.org/docs/advanced-features/custom-document

This handles the case where the children on a head element are undefined and not a string or an array of strings. This doesn't currently handle sub-children on head elements so additional handling will be needed if this is a feature we would like to support although can be discussed/investigated separately from this fix. 

Fixes: https://github.com/vercel/next.js/issues/17364  
Fixes: https://github.com/vercel/next.js/issues/6388
Closes: https://github.com/vercel/next.js/pull/16751

* Expose dotenv loading under separate package

* Update pre-compiled

* Rename package to @next/env

* Update lint ignores

* Update package.json
Co-authored-by: NJoe Haddad <joe.haddad@zeit.co>

Noticed while adding config checks for a new config that the `basePath` checks were wrapped in a `result.experimental` check and even though this should always be true from the default experimental value being an object the `basePath` checks shouldn't be wrapped in this check since it isn't experimental anymore. 

As clear from [#14233](https://github.com/vercel/next.js/pull/14233#issuecomment-645997757) that the 'with-algolia example is not SSR', I've updated the documentation to clear the confusion caused, as visible in #17229 

Fixes #17229

Wrong variable was being checked for the hydrate action on redux. This was causing the count to be reset to 0 instead of being 1 when initially loading index.js page.

Fixes #17299

The example has been emptied as it is no longer the recommended way to do it so it shouldn't be linked to

There was a blank line, this PR removes it :D

Prior to this pull request, Next.js would immediately decode all URLs sent to its server (via `path-match`).

This was rarely needed, and Next.js would typically re-encode the incoming request right away (see all the `encodeURIComponent`s removed in PR diff). This adds unnecessary performance overhead.

Long term, this will also help prevent weird encoding edge-cases like #10004, #10022, #11371, et al.

---

No new tests are necessary for this change because we've extensively tested these edge cases with existing tests.
One test was updated to reflect that we skip decoding in a 404 scenario.

Let's see if all the existing tests pass!