Fix for __dirname

packages/next/build/webpack-config.ts

@@ -314,6 +314,7 @@ export default async function getBaseWebpackConfig(
     mode: webpackMode,
     name: isServer ? 'server' : 'client',
     target: isServer ? 'node' : 'web',
+    cache: isServer && dev ? false : true,
     externals: !isServer
       ? undefined
       : !isServerless
@@ -501,6 +502,18 @@ export default async function getBaseWebpackConfig(
             include: [path.join(dir, 'data')],
             use: 'next-data-loader',
           },
+        isServer && {
+          test: /\.(tsx|ts|js|mjs|jsx|node)$/,
+          parser: { amd: false },
+          use: {
+            loader: '@zeit/webpack-asset-relocator-loader',
+            options: {
+              filterAssetBase: dir,
+              production: !dev,
+              debugLog: false,
+            },
+          },
+        },
         {
           test: /\.(tsx|ts|js|mjs|jsx)$/,
           include: [

packages/next/package.json

@@ -67,6 +67,7 @@
     "@babel/preset-typescript": "7.3.3",
     "@babel/runtime": "7.4.5",
     "@babel/runtime-corejs2": "7.4.5",
+    "@zeit/webpack-asset-relocator-loader": "0.6.2",
     "amphtml-validator": "1.0.23",
     "async-sema": "3.0.0",
     "autodll-webpack-plugin": "0.4.2",

test/integration/api-support/pages/api/dirname.js

@@ -0,0 +1,11 @@
+import fs from 'fs'
+import path from 'path'
+
+export default (req, res) => {
+  const fileContent = fs.readFileSync(
+    path.resolve(__dirname, '..', 'index.js'),
+    'utf8'
+  )
+
+  res.end(fileContent)
+}

test/integration/api-support/test/index.test.js

@@ -10,7 +10,8 @@ import {
   renderViaHTTP,
   nextBuild,
   nextStart,
-  File
+  File,
+  waitFor
 } from 'next-test-utils'
 import json from '../big.json'
 import { createServer } from 'http'
@@ -248,6 +249,49 @@ function runTests (serverless = false) {
     expect(res.status).toBe(404)
   })
 
+  it('should work with __dirname', async () => {
+    const data = await fetchViaHTTP(appPort, '/api/dirname', null, {}).then(
+      res => res.ok && res.text()
+    )
+
+    expect(data).toContain('export default () => <div>API - support</div>')
+  })
+
+  it('should work with __dirname and re-compile', async () => {
+    const data = await fetchViaHTTP(appPort, '/api/dirname', null, {}).then(
+      res => res.ok && res.text()
+    )
+
+    expect(data).toContain('export default () => <div>API - support</div>')
+
+    const index = new File(join(appDir, 'pages/index.js'))
+
+    index.replace('API', 'IPA')
+
+    await waitFor(500)
+
+    const change = await fetchViaHTTP(appPort, '/api/dirname', null, {}).then(
+      res => res.ok && res.text()
+    )
+    expect(change).toContain('export default () => <div>IPA - support</div>')
+
+    index.restore()
+
+    const dirname = new File(join(appDir, 'pages/api/dirname.js'))
+
+    dirname.replace('index.js', 'user.js')
+
+    await waitFor(500)
+
+    const user = await fetchViaHTTP(appPort, '/api/dirname', null, {}).then(
+      res => res.ok && res.text()
+    )
+
+    expect(user).toContain('export default () => <div>User</div>')
+
+    dirname.restore()
+  })
+
   it('should build api routes', async () => {
     await nextBuild(appDir, [], { stdout: true })
     if (serverless) {

yarn.lock

@@ -2601,6 +2601,13 @@
   dependencies:
     "@babel/preset-typescript" "^7.0.0"
 
+"@zeit/webpack-asset-relocator-loader@0.6.2":
+  version "0.6.2"
+  resolved "https://registry.yarnpkg.com/@zeit/webpack-asset-relocator-loader/-/webpack-asset-relocator-loader-0.6.2.tgz#b15353d8578562f299eddb94d4b771297acc0487"
+  integrity sha512-IUz2YvFAv03LHP4dhjHqG549ecZhdp7KU8B+vGfJRgcDzvlCmc9CA1YcYfJHVO96U8dU5z85RIysr2whYUXmgQ==
+  dependencies:
+    sourcemap-codec "^1.4.4"
+
 JSONStream@^1.0.4, JSONStream@^1.3.4:
   version "1.3.5"
   resolved "https://registry.yarnpkg.com/JSONStream/-/JSONStream-1.3.5.tgz#3208c1f08d3a4d99261ab64f92302bc15e111ca0"
@@ -12640,6 +12647,11 @@ source-map@^0.5.0, source-map@^0.5.3, source-map@^0.5.6:
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.7.tgz#8a039d2d1021d22d1ea14c80d8ea468ba2ef3fcc"
   integrity sha1-igOdLRAh0i0eoUyA2OpGi6LvP8w=
 
+sourcemap-codec@^1.4.4:
+  version "1.4.6"
+  resolved "https://registry.yarnpkg.com/sourcemap-codec/-/sourcemap-codec-1.4.6.tgz#e30a74f0402bad09807640d39e971090a08ce1e9"
+  integrity sha512-1ZooVLYFxC448piVLBbtOxFcXwnymH9oUF8nRd3CuYDVvkRBxRl6pB4Mtas5a4drtL+E8LDgFkQNcgIw6tc8Hg==
+
 spawn-sync@^1.0.15:
   version "1.0.15"
   resolved "https://registry.yarnpkg.com/spawn-sync/-/spawn-sync-1.0.15.tgz#b00799557eb7fb0c8376c29d44e8a1ea67e57476"