Closes: #6244
This will block the following keys:
```
NODE_.+
__.+
```
There doesn't seem to be a way to simulate a failed build or else I'd add tests for it.
original code in `/lib/router/router.js`
```
urlIsNew (pathname, query) {
return this.pathname !== pathname || !shallowEquals(query, this.query)
}
```
the urlIsNew compare `this.pathname` to an argument `pathname`
the invokers:
```
// If asked to change the current URL we should reload the current page
// (not location.reload() but reload getInitialProps and other Next.js stuffs)
// We also need to set the method = replaceState always
// as this should not go into the history (That's how browsers work)
if (!this.urlIsNew(asPathname, asQuery)) {
method = 'replaceState'
}
```
the parameter here is `asPathname` destructured from `asPath`
so here is a problem when we reuse a single page rendered in two asPaths
pages/a.js
```
<>
<Link href='/a'><a>goto a</a></Link>
<Link href='/a' as='/b'><a>goto b</a></Link>
</>
```
If we navigate to page /a, then click 'goto b', actually the history is replaced, not pushed.
It is expected that history could be correctly pushed and popped as long as the browser url is changed.
This PR fixes the buggy `Head.propTypes` here:
https://github.com/zeit/next.js/blob/v8.0.0-canary.3/packages/next-server/lib/head.js#L107
Currently, `Head.propTypes` allows one child node like this:
```jsx
import Head from 'next/head'
// …
<Head>
<title>Title</title>
</Head>
```
But more than one child node mistakenly causes a prop type error like this:
```jsx
<Head>
<title>Title</title>
<meta name="description" content="Description." />
</Head>
```
```
Warning: Failed prop type: Invalid prop `children` supplied to `Head`.
```
This PR aims at replacing next-server/lib/event-emitter.js by mitt.
Fix https://github.com/zeit/next.js/issues/4908
event-emitter.js is ~400 bytes gzipped vs mitt is 200 bytes
Saw a reply on the original pull request that the WebSocket using a random port broke their set up so I added a `--websocket` or `-w` argument similar to the `-p` argument to allow manually setting this port also.
Fixes#5845
Implement tslint for core files
**What is this?**
Implements tslint for both next and next-server, but keeps standardjs/eslint for the .js files that are still there, we're gradually migrating to Typescript.
**How does it work?**
Before every commit (pre-commit) we execute the following `tslint` command:
`tslint -c tslint.json 'packages/**/*.ts`
**TSLint Rules**
In order to avoid as much changes as possible I marked some rules as false. This way we can improve the linter but making sure this step will not break things. (see tslint.json)
**Note**
After merging this PR, you'll need to update your dependencies since it adds tslint to package.json
