Make sure animated assets aren't de-animated by optimizer

package.json

@@ -82,6 +82,7 @@
     "get-port": "5.1.1",
     "glob": "7.1.6",
     "gzip-size": "5.1.1",
+    "is-animated": "2.0.0",
     "isomorphic-unfetch": "3.0.0",
     "jest-circus": "26.0.1",
     "jest-cli": "24.9.0",

packages/next/compiled/is-animated/package.json

@@ -0,0 +1 @@
+{"name":"is-animated","main":"index.js","author":"Józef Sokołowski <j.k.sokolowski@gmail.com>","license":"MIT"}

packages/next/next-server/server/image-optimizer.ts

@@ -7,14 +7,18 @@ import { createHash } from 'crypto'
 import Server from './next-server'
 import { getContentType, getExtension } from './serve-static'
 import { fileExists } from '../../lib/file-exists'
+// @ts-ignore no types for is-animated
+import isAnimated from 'next/dist/compiled/is-animated'
 
 let sharp: typeof import('sharp')
 //const AVIF = 'image/avif'
 const WEBP = 'image/webp'
 const PNG = 'image/png'
 const JPEG = 'image/jpeg'
+const GIF = 'image/gif'
 const MIME_TYPES = [/* AVIF, */ WEBP, PNG, JPEG]
 const CACHE_VERSION = 1
+const ANIMATABLE_TYPES = [WEBP, PNG, GIF]
 
 export async function imageOptimizer(
   server: Server,
@@ -146,6 +150,18 @@ export async function imageOptimizer(
   const expireAt = maxAge * 1000 + now
   let contentType: string
 
+  if (
+    upstreamType &&
+    ANIMATABLE_TYPES.includes(upstreamType) &&
+    isAnimated(upstreamBuffer)
+  ) {
+    if (upstreamType) {
+      res.setHeader('Content-Type', upstreamType)
+    }
+    res.end(upstreamBuffer)
+    return { finished: true }
+  }
+
   if (mimeType) {
     contentType = mimeType
   } else if (upstreamType?.startsWith('image/') && getExtension(upstreamType)) {

packages/next/taskfile.js

@@ -241,6 +241,14 @@ export async function ncc_ignore_loader(task, opts) {
     .target('compiled/ignore-loader')
 }
 // eslint-disable-next-line camelcase
+externals['is-animated'] = 'next/dist/compiled/is-animated'
+export async function ncc_is_animated(task, opts) {
+  await task
+    .source(opts.src || relative(__dirname, require.resolve('is-animated')))
+    .ncc({ packageName: 'is-animated', externals })
+    .target('compiled/is-animated')
+}
+// eslint-disable-next-line camelcase
 externals['is-docker'] = 'next/dist/compiled/is-docker'
 export async function ncc_is_docker(task, opts) {
   await task
@@ -504,6 +512,7 @@ export async function ncc(task) {
       'ncc_gzip_size',
       'ncc_http_proxy',
       'ncc_ignore_loader',
+      'ncc_is_animated',
       'ncc_is_docker',
       'ncc_is_wsl',
       'ncc_json5',

test/integration/image-optimizer/test/index.test.js

@@ -1,6 +1,7 @@
 /* eslint-env jest */
 import fs from 'fs-extra'
 import { join } from 'path'
+import isAnimated from 'next/dist/compiled/is-animated'
 import {
   killApp,
   findPort,
@@ -40,6 +41,30 @@ function runTests({ w, isDev }) {
     expect(await res.text()).toMatch(/Image Optimizer Home/m)
   })
 
+  it('should maintain animated gif', async () => {
+    const query = { w, q: 90, url: '/animated.gif' }
+    const res = await fetchViaHTTP(appPort, '/_next/image', query, {})
+    expect(res.status).toBe(200)
+    expect(res.headers.get('content-type')).toContain('image/gif')
+    expect(isAnimated(await res.buffer())).toBe(true)
+  })
+
+  it('should maintain animated png', async () => {
+    const query = { w, q: 90, url: '/animated.png' }
+    const res = await fetchViaHTTP(appPort, '/_next/image', query, {})
+    expect(res.status).toBe(200)
+    expect(res.headers.get('content-type')).toContain('image/png')
+    expect(isAnimated(await res.buffer())).toBe(true)
+  })
+
+  it('should maintain animated webp', async () => {
+    const query = { w, q: 90, url: '/animated.webp' }
+    const res = await fetchViaHTTP(appPort, '/_next/image', query, {})
+    expect(res.status).toBe(200)
+    expect(res.headers.get('content-type')).toContain('image/webp')
+    expect(isAnimated(await res.buffer())).toBe(true)
+  })
+
   it('should fail when url is missing', async () => {
     const query = { w, q: 100 }
     const res = await fetchViaHTTP(appPort, '/_next/image', query, {})

yarn.lock

@@ -8878,6 +8878,11 @@ is-alphanumerical@^1.0.0:
     is-alphabetical "^1.0.0"
     is-decimal "^1.0.0"
 
+is-animated@2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/is-animated/-/is-animated-2.0.0.tgz#ffb1f180ff10782b8442dcb0955b5fc915e1a111"
+  integrity sha512-ZsfhGnSRUjto9owW5WpaDL7z/03H77Ny9JgP/BSyOQ/mAPAKNbdX30WNYbg2R5NhvT5VqKs2KL38znj5OG8tDg==
+
 is-arguments@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/is-arguments/-/is-arguments-1.0.4.tgz#3faf966c7cba0ff437fb31f6250082fcf0448cf3"