Compile away next/link proptypes in production (#5155)

This saves 7KB as prop-types-exact is not needed in production.

build/webpack.js

@@ -245,6 +245,15 @@ export default async function getBaseWebpackConfig (dir: string, {dev = false, i
       }),
       dev && !isServer && new FriendlyErrorsWebpackPlugin(),
       new webpack.IgnorePlugin(/(precomputed)/, /node_modules.+(elliptic)/),
+      // This removes prop-types-exact in production, as it's not used there.
+      !dev && new webpack.IgnorePlugin({
+        checkResource: (resource) => {
+          return /prop-types-exact/.test(resource)
+        },
+        checkContext: (context) => {
+          return context.indexOf(NEXT_PROJECT_ROOT_DIST) !== -1
+        }
+      }),
       // Even though require.cache is server only we have to clear assets from both compilations
       // This is because the client compilation generates the build manifest that's used on the server side
       dev && new NextJsRequireCacheHotReloader(),

lib/error.js

@@ -9,10 +9,6 @@ export default class Error extends React.Component {
     return { statusCode }
   }
 
-  static propTypes = {
-    statusCode: PropTypes.number
-  }
-
   render () {
     const { statusCode } = this.props
     const title = statusCode === 404
@@ -35,6 +31,12 @@ export default class Error extends React.Component {
   }
 }
 
+if (process.env.NODE_ENV === 'development') {
+  Error.propTypes = {
+    statusCode: PropTypes.number
+  }
+}
+
 const styles = {
   error: {
     color: '#000',

lib/link.js

@@ -3,7 +3,6 @@
 import { resolve, format, parse } from 'url'
 import React, { Component, Children } from 'react'
 import PropTypes from 'prop-types'
-import exact from 'prop-types-exact'
 import Router, { _rewriteUrlForNextExport } from './router'
 import { warn, execOnce, getLocationOrigin } from './utils'
 
@@ -35,28 +34,6 @@ function memoizedFormatUrl (formatUrl) {
 }
 
 class Link extends Component {
-  static propTypes = exact({
-    href: PropTypes.oneOfType([PropTypes.string, PropTypes.object]).isRequired,
-    as: PropTypes.oneOfType([PropTypes.string, PropTypes.object]),
-    prefetch: PropTypes.bool,
-    replace: PropTypes.bool,
-    shallow: PropTypes.bool,
-    passHref: PropTypes.bool,
-    scroll: PropTypes.bool,
-    children: PropTypes.oneOfType([
-      PropTypes.element,
-      (props, propName) => {
-        const value = props[propName]
-
-        if (typeof value === 'string') {
-          warnLink(`Warning: You're using a string directly inside <Link>. This usage has been deprecated. Please add an <a> tag as child of <Link>`)
-        }
-
-        return null
-      }
-    ]).isRequired
-  })
-
   componentDidMount () {
     this.prefetch()
   }
@@ -177,4 +154,30 @@ class Link extends Component {
   }
 }
 
+if (process.env.NODE_ENV === 'development') {
+  // This module gets removed by webpack.IgnorePlugin
+  const exact = require('prop-types-exact')
+  Link.propTypes = exact({
+    href: PropTypes.oneOfType([PropTypes.string, PropTypes.object]).isRequired,
+    as: PropTypes.oneOfType([PropTypes.string, PropTypes.object]),
+    prefetch: PropTypes.bool,
+    replace: PropTypes.bool,
+    shallow: PropTypes.bool,
+    passHref: PropTypes.bool,
+    scroll: PropTypes.bool,
+    children: PropTypes.oneOfType([
+      PropTypes.element,
+      (props, propName) => {
+        const value = props[propName]
+
+        if (typeof value === 'string') {
+          warnLink(`Warning: You're using a string directly inside <Link>. This usage has been deprecated. Please add an <a> tag as child of <Link>`)
+        }
+
+        return null
+      }
+    ]).isRequired
+  })
+}
+
 export default Link