Warn on No Cache in CI

errors/no-cache.md

@@ -0,0 +1,76 @@
+# No Cache Detected
+
+#### Why This Error Occurred
+
+A Next.js build was triggered in a continuous integration environment, but no cache was detected.
+
+This results in slower builds and can hurt Next.js' persistent caching of client-side bundles across builds.
+
+#### Possible Ways to Fix It
+
+> **Note**: If this is a new project, or being built for the first time in your CI, you can ignore this error.
+> However, you'll want to make sure it doesn't continue to happen and fix it if it does!
+
+Configure Next.js' cache to be persisted across builds. Next.js stores its cache in the `.next/cache` directory.
+
+Storing this folder across builds varies by CI provider. We've provided a list of a few common providers below.
+
+**ZEIT Now**
+
+Next.js caching is automatically configured for you. There's no action required on your part.
+
+**CircleCI**
+
+Edit your `save_cache` step in `.circleci/config.yml` to include `.next/cache`:
+
+```yaml
+steps:
+  - save_cache:
+      key: dependency-cache-{{ checksum "yarn.lock" }}
+      paths:
+        - ./node_modules
+        - ./.next/cache
+```
+
+If you do not have a `save_cache` key, please follow CircleCI's [documentation on setting up build caching](https://circleci.com/docs/2.0/caching/).
+
+**Travis CI**
+
+Add or merge the following into your `.travis.yml`:
+
+```yaml
+cache:
+  directories:
+    - $HOME/.cache/yarn
+    - node_modules
+    - .next/cache
+```
+
+**GitLab CI**
+
+Add or merge the following into your `.gitlab-ci.yml`:
+
+```yaml
+cache:
+  key: ${CI_COMMIT_REF_SLUG}
+  paths:
+    - node_modules/
+    - .next/cache/
+```
+
+**Netlify CI**
+
+It is **not possible** to cache custom build files on Netlify. Please contact their support and request they support this behavior.
+
+You can investigate using a 3rd party solution (e.g. [`cache-me-outside`](https://github.com/DavidWells/cache-me-outside)) to manually cache the Next.js output.
+
+**AWS CodeBuild**
+
+Add (or merge in) the following to your `buildspec.yml`:
+
+```yaml
+cache:
+  paths:
+    - 'node_modules/**/*' # Cache `node_modules` for faster `yarn` or `npm i`
+    - '.next/cache/**/*' # Cache Next.js for faster application rebuilds
+```

packages/next/build/index.ts

@@ -1,4 +1,5 @@
 import chalk from 'chalk'
+import ciEnvironment from 'ci-info'
 import fs from 'fs'
 import Worker from 'jest-worker'
 import mkdirpOrig from 'mkdirp'
@@ -47,6 +48,7 @@ import getBaseWebpackConfig from './webpack-config'
 import { getPageChunks } from './webpack/plugins/chunk-graph-plugin'
 import { writeBuildId } from './write-build-id'
 
+const fsAccess = promisify(fs.access)
 const fsUnlink = promisify(fs.unlink)
 const fsRmdir = promisify(fs.rmdir)
 const fsStat = promisify(fs.stat)
@@ -83,15 +85,34 @@ export default async function build(dir: string, conf = null): Promise<void> {
     )
   }
 
-  const buildSpinner = createSpinner({
-    prefixText: 'Creating an optimized production build',
-  })
-
   const config = loadConfig(PHASE_PRODUCTION_BUILD, dir, conf)
   const { target } = config
   const buildId = await generateBuildId(config.generateBuildId, nanoid)
   const distDir = path.join(dir, config.distDir)
 
+  if (ciEnvironment.isCI) {
+    const cacheDir = path.join(distDir, 'cache')
+    const hasCache = await fsAccess(cacheDir)
+      .then(() => true)
+      .catch(() => false)
+
+    if (!hasCache) {
+      // Intentionally not piping to stderr in case people fail in CI when
+      // stderr is detected.
+      console.log(
+        chalk.bold.yellow(`Warning: `) +
+          chalk.bold(
+            `No build cache found. Please configure build caching for faster rebuilds. Read more: https://err.sh/next.js/no-cache`
+          )
+      )
+      console.log('')
+    }
+  }
+
+  const buildSpinner = createSpinner({
+    prefixText: 'Creating an optimized production build',
+  })
+
   const telemetry = new Telemetry({ distDir })
 
   const publicDir = path.join(dir, 'public')

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

@@ -1,6 +1,7 @@
 /* eslint-env jest */
 /* global jasmine */
 import { join } from 'path'
+import { remove } from 'fs-extra'
 import { nextBuild, File, waitFor } from 'next-test-utils'
 
 jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 1
@@ -42,4 +43,36 @@ describe('Build warnings', () => {
 
     nextConfig.restore()
   })
+
+  it('should not warn about missing cache in non-CI', async () => {
+    await remove(join(appDir, '.next'))
+
+    const { stdout } = await nextBuild(appDir, undefined, {
+      stdout: true,
+      env: {
+        CI: '',
+        CIRCLECI: '',
+        TRAVIS: '',
+        SYSTEM_TEAMFOUNDATIONCOLLECTIONURI: ''
+      }
+    })
+    expect(stdout).not.toContain('no-cache')
+  })
+
+  it('should warn about missing cache in CI', async () => {
+    await remove(join(appDir, '.next'))
+
+    let { stdout } = await nextBuild(appDir, undefined, {
+      stdout: true,
+      env: { CI: '1' }
+    })
+    expect(stdout).toContain('no-cache')
+
+    // Do not warn after cache is present
+    ;({ stdout } = await nextBuild(appDir, undefined, {
+      stdout: true,
+      env: { CI: '1' }
+    }))
+    expect(stdout).not.toContain('no-cache')
+  })
 })