Add next/image default loader errors

packages/next/build/webpack-config.ts

@@ -994,6 +994,12 @@ export default async function getBaseWebpackConfig(
           sizes: config.images.sizes,
           path: config.images.path,
           loader: config.images.loader,
+          ...(dev
+            ? {
+                // pass domains in development to allow validating on the client
+                domains: config.images.domains,
+              }
+            : {}),
         }),
         'process.env.__NEXT_ROUTER_BASEPATH': JSON.stringify(config.basePath),
         'process.env.__NEXT_HAS_REWRITES': JSON.stringify(hasRewrites),

packages/next/client/image.tsx

@@ -17,6 +17,7 @@ type ImageData = {
   sizes: number[]
   loader: LoaderKey
   path: string
+  domains?: string[]
 }
 
 type ImageProps = Omit<
@@ -34,7 +35,12 @@ type ImageProps = Omit<
   )
 
 const imageData: ImageData = process.env.__NEXT_IMAGE_OPTS as any
-const { sizes: configSizes, loader: configLoader, path: configPath } = imageData
+const {
+  sizes: configSizes,
+  loader: configLoader,
+  path: configPath,
+  domains: configDomains,
+} = imageData
 configSizes.sort((a, b) => a - b) // smallest to largest
 const largestSize = configSizes[configSizes.length - 1]
 
@@ -349,6 +355,42 @@ function cloudinaryLoader({ root, src, width, quality }: LoaderProps): string {
 }
 
 function defaultLoader({ root, src, width, quality }: LoaderProps): string {
+  if (process.env.NODE_ENV !== 'production') {
+    const missingValues = []
+
+    // these should always be provided but make sure they are
+    if (!src) missingValues.push('src')
+    if (!width) missingValues.push('width')
+
+    if (missingValues.length > 0) {
+      throw new Error(
+        `Next Image Optimization requires ${missingValues.join(
+          ', '
+        )} to be provided. Make sure you pass them as props to the \`next/image\` component. Received: ${JSON.stringify(
+          { src, width, quality }
+        )}`
+      )
+    }
+
+    if (src && !src.startsWith('/') && configDomains) {
+      let parsedSrc: URL
+      try {
+        parsedSrc = new URL(src)
+      } catch (err) {
+        console.error(err)
+        throw new Error(
+          `Failed to parse "${src}" if using relative image it must start with a leading slash "/" or be an absolute URL`
+        )
+      }
+
+      if (!configDomains.includes(parsedSrc.hostname)) {
+        throw new Error(
+          `Invalid src prop (${src}) on \`next/image\`, hostname is not configured under images in your \`next.config.js\``
+        )
+      }
+    }
+  }
+
   return `${root}?url=${encodeURIComponent(src)}&w=${width}&q=${
     quality || '100'
   }`

test/integration/image-component/default/pages/invalid-src.js

@@ -0,0 +1,13 @@
+import React from 'react'
+import Image from 'next/image'
+
+const Page = () => {
+  return (
+    <div>
+      <p>Hello World</p>
+      <Image src="https://google.com/test.png" unsized></Image>
+    </div>
+  )
+}
+
+export default Page

test/integration/image-component/default/pages/missing-src.js

@@ -0,0 +1,12 @@
+import React from 'react'
+import Image from 'next/image'
+
+const Page = () => {
+  return (
+    <div>
+      <Image width={200}></Image>
+    </div>
+  )
+}
+
+export default Page

test/integration/image-component/default/test/index.test.js

@@ -8,6 +8,8 @@ import {
   nextStart,
   nextBuild,
   check,
+  hasRedbox,
+  getRedboxHeader,
 } from 'next-test-utils'
 import webdriver from 'next-webdriver'
 import fs from 'fs-extra'
@@ -20,7 +22,7 @@ const nextConfig = join(appDir, 'next.config.js')
 let appPort
 let app
 
-function runTests() {
+function runTests(mode) {
   it('should load the images', async () => {
     let browser
     try {
@@ -79,6 +81,26 @@ function runTests() {
       }
     }
   })
+
+  if (mode === 'dev') {
+    it('should show missing src error', async () => {
+      const browser = await webdriver(appPort, '/missing-src')
+
+      await hasRedbox(browser)
+      expect(await getRedboxHeader(browser)).toContain(
+        'Next Image Optimization requires src to be provided. Make sure you pass them as props to the `next/image` component. Received: {"width":1200}'
+      )
+    })
+
+    it('should show invalid src error', async () => {
+      const browser = await webdriver(appPort, '/invalid-src')
+
+      await hasRedbox(browser)
+      expect(await getRedboxHeader(browser)).toContain(
+        'Invalid src prop (https://google.com/test.png) on `next/image`, hostname is not configured under images in your `next.config.js`'
+      )
+    })
+  }
 }
 
 describe('Image Component Tests', () => {