fix(NODE_ENV): Warn when launching start or build on development

packages/next/bin/next.ts

@@ -88,8 +88,18 @@ const defaultEnv = command === 'dev' ? 'development' : 'production'
 
 const standardEnv = ['production', 'development', 'test']
 
-if (process.env.NODE_ENV && !standardEnv.includes(process.env.NODE_ENV)) {
-  log.warn(NON_STANDARD_NODE_ENV)
+if (process.env.NODE_ENV) {
+  const isNotStandard = !standardEnv.includes(process.env.NODE_ENV)
+  const shouldWarnCommands =
+    process.env.NODE_ENV === 'development'
+      ? ['start', 'build']
+      : process.env.NODE_ENV === 'production'
+      ? ['dev']
+      : []
+
+  if (isNotStandard || shouldWarnCommands.includes(command)) {
+    log.warn(NON_STANDARD_NODE_ENV)
+  }
 }
 
 ;(process.env as any).NODE_ENV = process.env.NODE_ENV || defaultEnv

test/integration/non-standard-node-env-warning/test/index.test.js

@@ -9,6 +9,7 @@ import {
   waitFor,
   initNextServerScript,
   nextBuild,
+  nextStart,
 } from 'next-test-utils'
 
 const appDir = join(__dirname, '..')
@@ -135,4 +136,47 @@ describe('Non-Standard NODE_ENV', () => {
     await killApp(app)
     expect(output).toContain(warningText)
   })
+
+  it('should show the warning with NODE_ENV set to production with next dev', async () => {
+    let output = ''
+
+    app = await launchApp(appDir, await findPort(), {
+      env: {
+        NODE_ENV: 'production',
+      },
+      onStderr(msg) {
+        output += msg || ''
+      },
+    })
+    await waitFor(2000)
+    await killApp(app)
+    expect(output).toContain(warningText)
+  })
+
+  it('should show the warning with NODE_ENV set to development with next build', async () => {
+    const { stderr } = await nextBuild(appDir, [], {
+      env: {
+        NODE_ENV: 'development',
+      },
+      stderr: true,
+    })
+    expect(stderr).toContain(warningText)
+  })
+
+  it('should show the warning with NODE_ENV set to development with next start', async () => {
+    let output = ''
+
+    await nextBuild(appDir)
+    app = await nextStart(appDir, await findPort(), {
+      env: {
+        NODE_ENV: 'development',
+      },
+      onStderr(msg) {
+        output += msg || ''
+      },
+    })
+    await waitFor(2000)
+    await killApp(app)
+    expect(output).toContain(warningText)
+  })
 })