Image component foundation (#17343)

Co-authored-by: Tim Neutkens <timneutkens@me.com>
Co-authored-by: Tim Neutkens <tim@timneutkens.nl>

packages/next/build/webpack-config.ts

@@ -229,6 +229,25 @@ export default async function getBaseWebpackConfig(
     }
   }
 
+  if (config.images?.hosts) {
+    if (!config.images.hosts.default) {
+      // If the image component is being used, a default host must be provided
+      throw new Error(
+        'If the image configuration property is present in next.config.js, it must have a host named "default"'
+      )
+    }
+    Object.values(config.images.hosts).forEach((host: any) => {
+      if (!host.path) {
+        throw new Error(
+          'All hosts defined in the image configuration property of next.config.js must define a path'
+        )
+      }
+      // Normalize hosts so all paths have trailing slash
+      if (host.path[host.path.length - 1] !== '/') {
+        host.path += '/'
+      }
+    })
+  }
   const reactVersion = await getPackageVersion({ cwd: dir, name: 'react' })
   const hasReactRefresh: boolean = dev && !isServer
   const hasJsxRuntime: boolean =
@@ -583,6 +602,7 @@ export default async function getBaseWebpackConfig(
       'next/app',
       'next/document',
       'next/link',
+      'next/image',
       'next/error',
       'string-hash',
       'next/constants',
@@ -984,6 +1004,7 @@ export default async function getBaseWebpackConfig(
         'process.env.__NEXT_SCROLL_RESTORATION': JSON.stringify(
           config.experimental.scrollRestoration
         ),
+        'process.env.__NEXT_IMAGE_OPTS': JSON.stringify(config.images),
         'process.env.__NEXT_ROUTER_BASEPATH': JSON.stringify(config.basePath),
         'process.env.__NEXT_HAS_REWRITES': JSON.stringify(hasRewrites),
         'process.env.__NEXT_i18n_SUPPORT': JSON.stringify(

packages/next/build/webpack/loaders/next-serverless-loader.ts

@@ -684,7 +684,6 @@ const nextServerlessLoader: loader.Loader = function () {
 
         const previewData = tryGetPreviewData(req, res, options.previewProps)
         const isPreviewMode = previewData !== false
-
         if (process.env.__NEXT_OPTIMIZE_FONTS) {
           renderOpts.optimizeFonts = true
           /**

packages/next/client/image.tsx

@@ -0,0 +1,183 @@
+import React, { ReactElement } from 'react'
+import Head from '../next-server/lib/head'
+
+const loaders: { [key: string]: (props: LoaderProps) => string } = {
+  imgix: imgixLoader,
+  cloudinary: cloudinaryLoader,
+  default: defaultLoader,
+}
+type ImageData = {
+  hosts: {
+    [key: string]: {
+      path: string
+      loader: string
+    }
+  }
+  breakpoints?: number[]
+}
+
+type ImageProps = {
+  src: string
+  host: string
+  sizes: string
+  breakpoints: number[]
+  priority: boolean
+  unoptimized: boolean
+  rest: any[]
+}
+
+let imageData: any = process.env.__NEXT_IMAGE_OPTS
+const breakpoints = imageData.breakpoints || [640, 1024, 1600]
+
+function computeSrc(src: string, host: string, unoptimized: boolean): string {
+  if (unoptimized) {
+    return src
+  }
+  if (!host) {
+    // No host provided, use default
+    return callLoader(src, 'default')
+  } else {
+    let selectedHost = imageData.hosts[host]
+    if (!selectedHost) {
+      if (process.env.NODE_ENV !== 'production') {
+        console.error(
+          `Image tag is used specifying host ${host}, but that host is not defined in next.config`
+        )
+      }
+      return src
+    }
+    return callLoader(src, host)
+  }
+}
+
+function callLoader(src: string, host: string, width?: number): string {
+  let loader = loaders[imageData.hosts[host].loader || 'default']
+  return loader({ root: imageData.hosts[host].path, filename: src, width })
+}
+
+type SrcSetData = {
+  src: string
+  host: string
+  widths: number[]
+}
+
+function generateSrcSet({ src, host, widths }: SrcSetData): string {
+  // At each breakpoint, generate an image url using the loader, such as:
+  // ' www.example.com/foo.jpg?w=480 480w, '
+  return widths
+    .map((width: number) => `${callLoader(src, host, width)} ${width}w`)
+    .join(', ')
+}
+
+type PreloadData = {
+  src: string
+  host: string
+  widths: number[]
+  sizes: string
+  unoptimized: boolean
+}
+
+function generatePreload({
+  src,
+  host,
+  widths,
+  unoptimized,
+  sizes,
+}: PreloadData): ReactElement {
+  // This function generates an image preload that makes use of the "imagesrcset" and "imagesizes"
+  // attributes for preloading responsive images. They're still experimental, but fully backward
+  // compatible, as the link tag includes all necessary attributes, even if the final two are ignored.
+  // See: https://web.dev/preload-responsive-images/
+  return (
+    <Head>
+      <link
+        rel="preload"
+        as="image"
+        href={computeSrc(src, host, unoptimized)}
+        // @ts-ignore: imagesrcset and imagesizes not yet in the link element type
+        imagesrcset={generateSrcSet({ src, host, widths })}
+        imagesizes={sizes}
+      />
+    </Head>
+  )
+}
+
+export default function Image({
+  src,
+  host,
+  sizes,
+  unoptimized,
+  priority,
+  ...rest
+}: ImageProps) {
+  // Sanity Checks:
+  if (process.env.NODE_ENV !== 'production') {
+    if (unoptimized && host) {
+      console.error(`Image tag used specifying both a host and the unoptimized attribute--these are mutually exclusive. 
+          With the unoptimized attribute, no host will be used, so specify an absolute URL.`)
+    }
+  }
+  if (host && !imageData.hosts[host]) {
+    // If unregistered host is selected, log an error and use the default instead
+    if (process.env.NODE_ENV !== 'production') {
+      console.error(`Image host identifier ${host} could not be resolved.`)
+    }
+    host = 'default'
+  }
+
+  host = host || 'default'
+
+  // Normalize provided src
+  if (src[0] === '/') {
+    src = src.slice(1)
+  }
+
+  // Generate attribute values
+  const imgSrc = computeSrc(src, host, unoptimized)
+  const imgAttributes: { src: string; srcSet?: string } = { src: imgSrc }
+  if (!unoptimized) {
+    imgAttributes.srcSet = generateSrcSet({
+      src,
+      host: host,
+      widths: breakpoints,
+    })
+  }
+  // No need to add preloads on the client side--by the time the application is hydrated,
+  // it's too late for preloads
+  const shouldPreload = priority && typeof window === 'undefined'
+
+  return (
+    <div>
+      {shouldPreload
+        ? generatePreload({
+            src,
+            host,
+            widths: breakpoints,
+            unoptimized,
+            sizes,
+          })
+        : ''}
+      <img {...rest} {...imgAttributes} sizes={sizes} />
+    </div>
+  )
+}
+
+//BUILT IN LOADERS
+
+type LoaderProps = {
+  root: string
+  filename: string
+  width?: number
+}
+
+function imgixLoader({ root, filename, width }: LoaderProps): string {
+  return `${root}${filename}${width ? '?w=' + width : ''}`
+}
+
+function cloudinaryLoader({ root, filename, width }: LoaderProps): string {
+  return `${root}${width ? 'w_' + width + '/' : ''}${filename}`
+}
+
+function defaultLoader({ root, filename }: LoaderProps): string {
+  return `${root}${filename}`
+}

packages/next/image.d.ts

@@ -0,0 +1,2 @@
+export * from './dist/client/image'
+export { default } from './dist/client/image'

packages/next/image.js

@@ -0,0 +1 @@
+module.exports = require('./dist/client/image')

packages/next/next-server/server/config.ts

@@ -23,6 +23,7 @@ const defaultConfig: { [key: string]: any } = {
   target: 'server',
   poweredByHeader: true,
   compress: true,
+  images: { hosts: { default: { path: 'defaultconfig' } } },
   devIndicators: {
     buildActivity: true,
     autoPrerender: true,

packages/next/next-server/server/next-server.ts

@@ -137,6 +137,7 @@ export default class Server {
     ampOptimizerConfig?: { [key: string]: any }
     basePath: string
     optimizeFonts: boolean
+    images: string
     fontManifest: FontManifest
     optimizeImages: boolean
     locale?: string
@@ -188,6 +189,7 @@ export default class Server {
       customServer: customServer === true ? true : undefined,
       ampOptimizerConfig: this.nextConfig.experimental.amp?.optimizer,
       basePath: this.nextConfig.basePath,
+      images: JSON.stringify(this.nextConfig.images),
       optimizeFonts: this.nextConfig.experimental.optimizeFonts && !dev,
       fontManifest:
         this.nextConfig.experimental.optimizeFonts && !dev

test/integration/image-component/bad-next-config/pages/index.js

@@ -0,0 +1,7 @@
+import React from 'react'
+
+const page = () => {
+  return <div>Hello</div>
+}
+
+export default page

test/integration/image-component/bad-next-config/test/index.test.js

@@ -0,0 +1,76 @@
+/* eslint-env jest */
+
+import { join } from 'path'
+import { nextBuild } from 'next-test-utils'
+import fs from 'fs-extra'
+
+jest.setTimeout(1000 * 30)
+
+const appDir = join(__dirname, '../')
+const nextConfig = join(appDir, 'next.config.js')
+
+describe('Next.config.js images prop without default host', () => {
+  let build
+  beforeAll(async () => {
+    await fs.writeFile(
+      nextConfig,
+      `module.exports = {
+        images: {
+          hosts: {
+            secondary: {
+              path: 'https://examplesecondary.com/images/',
+              loader: 'cloudinary',
+            },
+          },
+          breakpoints: [480, 1024, 1600],
+        },
+      }`,
+      'utf8'
+    )
+    build = await nextBuild(appDir, [], {
+      stdout: true,
+      stderr: true,
+    })
+  })
+  it('Should error during build if images prop in next.config is malformed', () => {
+    expect(build.stderr).toContain(
+      'If the image configuration property is present in next.config.js, it must have a host named "default"'
+    )
+  })
+})
+
+describe('Next.config.js images prop without path', () => {
+  let build
+  beforeAll(async () => {
+    await fs.writeFile(
+      nextConfig,
+      `module.exports = {
+        images: {
+          hosts: {
+            default: {
+              path: 'https://examplesecondary.com/images/',
+              loader: 'cloudinary',
+            },
+            secondary: {
+              loader: 'cloudinary',
+            },
+          },
+          breakpoints: [480, 1024, 1600],
+        },
+      }`,
+      'utf8'
+    )
+    build = await nextBuild(appDir, [], {
+      stdout: true,
+      stderr: true,
+    })
+  })
+  afterAll(async () => {
+    await fs.remove(nextConfig)
+  })
+  it('Should error during build if images prop in next.config is malformed', () => {
+    expect(build.stderr).toContain(
+      'All hosts defined in the image configuration property of next.config.js must define a path'
+    )
+  })
+})

test/integration/image-component/basic/next.config.js

@@ -0,0 +1,15 @@
+module.exports = {
+  images: {
+    hosts: {
+      default: {
+        path: 'https://example.com/myaccount/',
+        loader: 'imgix',
+      },
+      secondary: {
+        path: 'https://examplesecondary.com/images/',
+        loader: 'cloudinary',
+      },
+    },
+    breakpoints: [480, 1024, 1600],
+  },
+}

test/integration/image-component/basic/pages/client-side.js

@@ -0,0 +1,31 @@
+import React from 'react'
+import Image from 'next/image'
+import Link from 'next/link'
+
+const ClientSide = () => {
+  return (
+    <div>
+      <p id="stubtext">This is a client side page</p>
+      <Image id="basic-image" src="foo.jpg"></Image>
+      <Image id="attribute-test" data-demo="demo-value" src="bar.jpg" />
+      <Image
+        id="secondary-image"
+        data-demo="demo-value"
+        host="secondary"
+        src="foo2.jpg"
+      />
+      <Image
+        id="unoptimized-image"
+        unoptimized
+        src="https://arbitraryurl.com/foo.jpg"
+      />
+      <Image id="priority-image-client" priority src="withpriorityclient.png" />
+      <Image id="preceding-slash-image" src="/fooslash.jpg" priority />
+      <Link href="/errors">
+        <a id="errorslink">Errors</a>
+      </Link>
+    </div>
+  )
+}
+
+export default ClientSide