next-upgrade: change --turbo to --turbopack if applicable (#71737)

packages/next-codemod/bin/__testfixtures__/change-turbo-to-turbopack/README.md

@@ -0,0 +1 @@
+Change `--turbo` to `--turbopack` in `next dev` script.

packages/next-codemod/bin/__testfixtures__/change-turbo-to-turbopack/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "change-turbo-to-turbopack",
+  "scripts": {
+    "dev": "next dev --turbo"
+  },
+  "dependencies": {
+    "next": "15.0.0-canary.0",
+    "react": "19.0.0-rc.0",
+    "react-dom": "19.0.0-rc.0"
+  }
+}

packages/next-codemod/bin/__testfixtures__/suggest-turbopack/README.md

@@ -0,0 +1 @@
+Suggest adding `--turbopack` to `next dev` script.

packages/next-codemod/bin/__testfixtures__/suggest-turbopack/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "suggest-turbopack",
+  "scripts": {
+    "dev": "next dev"
+  },
+  "dependencies": {
+    "next": "15.0.0-canary.0",
+    "react": "19.0.0-rc.0",
+    "react-dom": "19.0.0-rc.0"
+  }
+}

packages/next-codemod/bin/upgrade.ts

@@ -177,7 +177,7 @@ export async function runUpgrade(
       )
 
   if (compareVersions(targetNextVersion, '15.0.0-canary') >= 0) {
-    await suggestTurbopack(appPackageJson)
+    await suggestTurbopack(appPackageJson, targetNextVersion)
   }
 
   const codemods = await suggestCodemods(
@@ -410,19 +410,37 @@ function isUsingAppDir(projectPath: string): boolean {
  * 3. Otherwise, we ask the user to manually add `--turbopack` to their dev command,
  *    showing the current dev command as the initial value.
  */
-async function suggestTurbopack(packageJson: any): Promise<void> {
+async function suggestTurbopack(
+  packageJson: any,
+  targetNextVersion: string
+): Promise<void> {
   const devScript: string = packageJson.scripts['dev']
+  // Turbopack flag was changed from `--turbo` to `--turbopack` in v15.0.1-canary.3
+  // PR: https://github.com/vercel/next.js/pull/71657
+  // Release: https://github.com/vercel/next.js/releases/tag/v15.0.1-canary.3
+  const isAfterTurbopackFlagChange =
+    compareVersions(targetNextVersion, '15.0.1-canary.3') >= 0
+  const turboPackFlag = isAfterTurbopackFlagChange ? '--turbopack' : '--turbo'
 
   if (!devScript) {
     console.log(
-      `${pc.red('⨯')} Could not find a "dev" script in your package.json.`
+      `${pc.yellow('⚠')} No "dev" script found in your package.json. Skipping Turbopack suggestion.`
     )
     return
   }
 
   if (devScript.includes('next dev')) {
     // covers "--turbopack" as well
     if (devScript.includes('--turbo')) {
+      if (isAfterTurbopackFlagChange && !devScript.includes('--turbopack')) {
+        console.log() // new line
+        console.log(
+          `${pc.green('✔')} Replaced "--turbo" with "--turbopack" in your dev script.`
+        )
+        console.log() // new line
+        packageJson.scripts['dev'] = devScript.replace('--turbo', '--turbopack')
+        return
+      }
       return
     }
 
@@ -442,7 +460,7 @@ async function suggestTurbopack(packageJson: any): Promise<void> {
 
     packageJson.scripts['dev'] = devScript.replace(
       'next dev',
-      'next dev --turbopack'
+      `next dev ${turboPackFlag}`
     )
     return
   }
@@ -455,7 +473,7 @@ async function suggestTurbopack(packageJson: any): Promise<void> {
     {
       type: 'text',
       name: 'customDevScript',
-      message: 'Please manually add "--turbopack" to your dev command.',
+      message: `Please manually add "${turboPackFlag}" to your dev command.`,
       initial: devScript,
     },
     { onCancel }