Move sharp to optionalDependencies (#18068)

Co-authored-by: NTim Neutkens <tim@timneutkens.nl>

errors/install-sharp.md

@@ -2,14 +2,27 @@
 
 #### Why This Error Occurred
 
-Using Next.js' built-in Image Optimization requires that you bring your own version of `sharp`.
+Using Next.js' built-in Image Optimization requires that you install `sharp`.
+
+Since `sharp` is optional, it may have been skipped if you installed `next` with the [`--no-optional`](https://docs.npmjs.com/cli/install) flag or it may have been skipped if your platform does not support `sharp`.
 
 #### Possible Ways to Fix It
 
-Please install the `sharp` package in your project.
+Option 1: Install the `sharp` package in your project.
 
 ```bash
 npm i sharp
 # or
 yarn add sharp
 ```
+
+Option 2: Configure an external loader in `next.config.js` such as [imgix](https://imgix.com).
+
+```js
+module.exports = {
+  images: {
+    path: 'https://example.com/myaccount/',
+    loader: 'imgix',
+  },
+}
+```

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

@@ -229,11 +229,12 @@ export async function imageOptimizer(
       sharp = require('sharp')
     } catch (error) {
       if (error.code === 'MODULE_NOT_FOUND') {
-        error.message +=
-          "\nTo use Next.js' built-in Image Optimization, you first need to install `sharp`."
-        error.message +=
-          '\nRun `npm i sharp` or `yarn add sharp` inside your workspace.'
         error.message += '\n\nLearn more: https://err.sh/next.js/install-sharp'
+        server.logError(error)
+        if (upstreamType) {
+          res.setHeader('Content-Type', upstreamType)
+        }
+        res.end(upstreamBuffer)
       }
       throw error
     }

packages/next/package.json

@@ -125,6 +125,9 @@
     "react": "^16.6.0",
     "react-dom": "^16.6.0"
   },
+  "optionalDependencies": {
+    "sharp": "0.26.2"
+  },
   "devDependencies": {
     "@next/polyfill-nomodule": "9.5.6-canary.9",
     "@taskr/clear": "1.1.0",
@@ -205,7 +208,6 @@
     "resolve": "1.11.0",
     "semver": "7.3.2",
     "send": "0.17.1",
-    "sharp": "0.26.2",
     "source-map": "0.6.1",
     "string-hash": "1.1.3",
     "strip-ansi": "6.0.0",