Bump minimum suggested React version

.github/workflows/build_test_deploy.yml

@@ -154,7 +154,7 @@ jobs:
       - run: exit 0
 
   testFutureDependencies:
-    name: React 17 + webpack 5 (Basic, Production, Acceptance)
+    name: Webpack 5 (Basic, Production, Acceptance)
     runs-on: ubuntu-latest
     env:
       NEXT_TELEMETRY_DISABLED: 1
@@ -171,16 +171,42 @@ jobs:
       - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*
         if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
 
-      - run: cat package.json | jq '.resolutions.react = "^17.0.1"' > package.json.tmp && mv package.json.tmp package.json
+      - run: yarn install --check-files
+        if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
+
+      - run: yarn list webpack
+        if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
+
+      - run: xvfb-run node run-tests.js test/integration/{link-ref,production,basic,async-modules,ssr-ctx}/test/index.test.js test/acceptance/*.test.js
+        if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
+
+  testLegacyReact:
+    name: React 16 + Webpack 4 (Basic, Production, Acceptance)
+    runs-on: ubuntu-latest
+    env:
+      NEXT_TELEMETRY_DISABLED: 1
+      NEXT_TEST_JOB: 1
+      HEADLESS: true
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - run: echo ::set-output name=DOCS_CHANGE::$(node skip-docs-change.js echo 'docs-only')
+        id: docs-change
+
+      - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*
+        if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
+
+      - run: cat package.json | jq '.resolutions.react = "^16.14.0"' > package.json.tmp && mv package.json.tmp package.json
         if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
 
-      - run: cat package.json | jq '.resolutions."react-dom" = "^17.0.1"' > package.json.tmp && mv package.json.tmp package.json
+      - run: cat package.json | jq '.resolutions."react-dom" = "^16.14.0"' > package.json.tmp && mv package.json.tmp package.json
         if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
 
       - run: yarn install --check-files
         if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
 
-      - run: yarn list webpack react react-dom
+      - run: yarn list react react-dom
         if: ${{ steps.docs-change.outputs.DOCS_CHANGE != 'docs-only' }}
 
       - run: xvfb-run node run-tests.js test/integration/{link-ref,production,basic,async-modules,ssr-ctx,worker-loader}/test/index.test.js test/acceptance/*.test.js

errors/react-version.md

@@ -5,7 +5,7 @@
 Your project is using an old version of `react` or `react-dom` that does not
 meet the suggested minimum version requirement.
 
-Next.js suggests using, at a minimum, `react@16.10.0` and `react-dom@16.10.0`.
+Next.js suggests using, at a minimum, `react@17.0.1` and `react-dom@17.0.1`.
 Older versions of `react` and `react-dom` do work with Next.js, however, they do
 not enable all of Next.js' features.
 
@@ -39,8 +39,8 @@ yarn add react@latest react-dom@latest
 ```json
 {
   "dependencies": {
-    "react": "^16.10.0",
-    "react-dom": "^16.10.0"
+    "react": "^17.0.1",
+    "react-dom": "^17.0.1"
   }
 }
 ```

package.json

@@ -115,8 +115,8 @@
     "prettier": "2.0.5",
     "pretty-bytes": "5.3.0",
     "pretty-ms": "7.0.0",
-    "react": "16.12.0",
-    "react-dom": "16.12.0",
+    "react": "17.0.1",
+    "react-dom": "17.0.1",
     "react-ssr-prepass": "1.0.8",
     "release": "6.3.0",
     "request-promise-core": "1.1.2",

packages/next/build/webpack/plugins/font-stylesheet-gathering-plugin.ts

@@ -122,6 +122,10 @@ export class FontStylesheetGatheringPlugin {
           parser.hooks.call
             .for('__jsx')
             .tap(this.constructor.name, jsxNodeHandler)
+          // New React JSX transform:
+          parser.hooks.call
+            .for('imported var')
+            .tap(this.constructor.name, jsxNodeHandler)
         })
     }
   }

packages/next/cli/next-build.ts

@@ -55,11 +55,50 @@ const nextBuild: cliCommand = (argv) => {
     printAndExit(`> No such directory exists as the project root: ${dir}`)
   }
 
-  return build(dir, null, args['--profile'], args['--debug']).catch((err) => {
-    console.error('')
-    console.error('> Build error occurred')
-    printAndExit(err)
-  })
+  async function preflight() {
+    const { getPackageVersion } = await import('../lib/get-package-version')
+    const semver = await import('next/dist/compiled/semver').then(
+      (res) => res.default
+    )
+
+    const reactVersion: string | null = await getPackageVersion({
+      cwd: dir,
+      name: 'react',
+    })
+    if (
+      reactVersion &&
+      semver.lt(reactVersion, '17.0.1') &&
+      semver.coerce(reactVersion)?.version !== '0.0.0'
+    ) {
+      Log.warn(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.' +
+          ' Read more: https://err.sh/next.js/react-version'
+      )
+    } else {
+      const reactDomVersion: string | null = await getPackageVersion({
+        cwd: dir,
+        name: 'react-dom',
+      })
+      if (
+        reactDomVersion &&
+        semver.lt(reactDomVersion, '17.0.1') &&
+        semver.coerce(reactDomVersion)?.version !== '0.0.0'
+      ) {
+        Log.warn(
+          'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.' +
+            ' Read more: https://err.sh/next.js/react-version'
+        )
+      }
+    }
+  }
+
+  return preflight()
+    .then(() => build(dir, null, args['--profile'], args['--debug']))
+    .catch((err) => {
+      console.error('')
+      console.error('> Build error occurred')
+      printAndExit(err)
+    })
 }
 
 export { nextBuild }

packages/next/cli/next-dev.ts

@@ -68,11 +68,11 @@ const nextDev: cliCommand = (argv) => {
     })
     if (
       reactVersion &&
-      semver.lt(reactVersion, '16.10.0') &&
+      semver.lt(reactVersion, '17.0.1') &&
       semver.coerce(reactVersion)?.version !== '0.0.0'
     ) {
       Log.warn(
-        'Fast Refresh is disabled in your application due to an outdated `react` version. Please upgrade 16.10 or newer!' +
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.' +
           ' Read more: https://err.sh/next.js/react-version'
       )
     } else {
@@ -82,11 +82,11 @@ const nextDev: cliCommand = (argv) => {
       })
       if (
         reactDomVersion &&
-        semver.lt(reactDomVersion, '16.10.0') &&
+        semver.lt(reactDomVersion, '17.0.1') &&
         semver.coerce(reactDomVersion)?.version !== '0.0.0'
       ) {
         Log.warn(
-          'Fast Refresh is disabled in your application due to an outdated `react-dom` version. Please upgrade 16.10 or newer!' +
+          'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.' +
             ' Read more: https://err.sh/next.js/react-version'
         )
       }

test/integration/build-output/test/index.test.js

@@ -94,17 +94,17 @@ describe('Build Output', () => {
       expect(parseFloat(indexSize) - 266).toBeLessThanOrEqual(0)
       expect(indexSize.endsWith('B')).toBe(true)
 
-      // should be no bigger than 62.2 kb
-      expect(parseFloat(indexFirstLoad)).toBeCloseTo(62.4, 1)
+      // should be no bigger than 63.8 kb
+      expect(parseFloat(indexFirstLoad)).toBeCloseTo(63.8, 1)
       expect(indexFirstLoad.endsWith('kB')).toBe(true)
 
       expect(parseFloat(err404Size) - 3.7).toBeLessThanOrEqual(0)
       expect(err404Size.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(err404FirstLoad)).toBeCloseTo(65.6, 1)
+      expect(parseFloat(err404FirstLoad)).toBeCloseTo(67, 1)
       expect(err404FirstLoad.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(sharedByAll)).toBeCloseTo(62.1, 1)
+      expect(parseFloat(sharedByAll)).toBeCloseTo(63.5, 1)
       expect(sharedByAll.endsWith('kB')).toBe(true)
 
       if (_appSize.endsWith('kB')) {
@@ -121,7 +121,7 @@ describe('Build Output', () => {
       expect(parseFloat(mainSize) - 7.3).toBeLessThanOrEqual(0)
       expect(mainSize.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(frameworkSize) - 42).toBeLessThanOrEqual(0)
+      expect(parseFloat(frameworkSize) - 42.1).toBeLessThanOrEqual(0)
       expect(frameworkSize.endsWith('kB')).toBe(true)
     })
 
@@ -168,7 +168,7 @@ describe('Build Output', () => {
       expect(parseFloat(indexSize)).toBeGreaterThanOrEqual(2)
       expect(indexSize.endsWith('kB')).toBe(true)
 
-      expect(parseFloat(indexFirstLoad)).toBeLessThanOrEqual(65.2)
+      expect(parseFloat(indexFirstLoad)).toBeLessThanOrEqual(66.6)
       expect(parseFloat(indexFirstLoad)).toBeGreaterThanOrEqual(60)
       expect(indexFirstLoad.endsWith('kB')).toBe(true)
     })

test/integration/cli/test/index.test.js

@@ -115,6 +115,69 @@ describe('CLI Usage', () => {
       expect(code).toBe(expectedExitCode)
       expect(signal).toBe(expectedExitSignal)
     })
+
+    test('too old of react version', async () => {
+      const { stderr } = await runNextCommand(['build', dirOldReact], {
+        stderr: true,
+      })
+
+      expect(stderr).toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
+
+    test('too old of react-dom version', async () => {
+      const { stderr } = await runNextCommand(['build', dirOldReactDom], {
+        stderr: true,
+      })
+
+      expect(stderr).toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
+
+    test('experimental react version', async () => {
+      const { stderr } = await runNextCommand(['build', dirExperimentalReact], {
+        stderr: true,
+      })
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
+
+    test('experimental react-dom version', async () => {
+      const { stderr } = await runNextCommand(
+        ['build', dirExperimentalReactDom],
+        {
+          stderr: true,
+        }
+      )
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
+
+    test('recommended react version', async () => {
+      const { stderr } = await runNextCommand(['build'], {
+        stderr: true,
+      })
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
+
+    test('recommended react-dom version', async () => {
+      const { stderr } = await runNextCommand(['build'], {
+        stderr: true,
+      })
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+    })
   })
 
   describe('dev', () => {
@@ -296,9 +359,8 @@ describe('CLI Usage', () => {
       })
 
       expect(stderr).toMatch(
-        'Fast Refresh is disabled in your application due to an outdated `react` version'
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
       )
-      expect(stderr).not.toMatch(`react-dom`)
 
       await killApp(instance)
     })
@@ -315,9 +377,8 @@ describe('CLI Usage', () => {
       })
 
       expect(stderr).toMatch(
-        'Fast Refresh is disabled in your application due to an outdated `react-dom` version'
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
       )
-      expect(stderr).not.toMatch('`react`')
 
       await killApp(instance)
     })
@@ -333,9 +394,9 @@ describe('CLI Usage', () => {
         },
       })
 
-      expect(stderr).not.toMatch('disabled')
-      expect(stderr).not.toMatch('outdated')
-      expect(stderr).not.toMatch(`react-dom`)
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
 
       await killApp(instance)
     })
@@ -351,9 +412,45 @@ describe('CLI Usage', () => {
         },
       })
 
-      expect(stderr).not.toMatch('disabled')
-      expect(stderr).not.toMatch('outdated')
-      expect(stderr).not.toMatch('`react`')
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+
+      await killApp(instance)
+    })
+
+    test('recommended react version', async () => {
+      const port = await findPort()
+
+      let stderr = ''
+      let instance = await launchApp(dir, port, {
+        stderr: true,
+        onStderr(msg) {
+          stderr += msg
+        },
+      })
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
+
+      await killApp(instance)
+    })
+
+    test('recommended react-dom version', async () => {
+      const port = await findPort()
+
+      let stderr = ''
+      let instance = await launchApp(dir, port, {
+        stderr: true,
+        onStderr(msg) {
+          stderr += msg
+        },
+      })
+
+      expect(stderr).not.toMatch(
+        'React 17.0.1 or newer will be required to leverage all of the upcoming features in Next.js 11.'
+      )
 
       await killApp(instance)
     })

test/integration/size-limit/test/index.test.js

@@ -81,6 +81,6 @@ describe('Production response size', () => {
     const delta = responseSizesBytes / 1024
 
     // Expected difference: < 0.5
-    expect(delta).toBeCloseTo(282.6, 0)
+    expect(delta).toBeCloseTo(284.1, 0)
   })
 })