fix: clear require cache after upgrade, before migrate

Author: haoqunjiang

packages/@vue/cli/lib/Upgrader.js

@@ -21,6 +21,10 @@ const PackageManager = require('./util/ProjectPackageManager')
 
 const { runMigrator } = require('./migrate')
 
+function clearRequireCache () {
+  Object.keys(require.cache).forEach(key => delete require.cache[key])
+}
+
 module.exports = class Upgrader {
   constructor (context = process.cwd()) {
     this.context = context
@@ -104,12 +108,16 @@ module.exports = class Upgrader {
 
     log(`Upgrading ${packageName} from ${installed} to ${targetVersion}`)
     await this.pm.upgrade(`${packageName}@~${targetVersion}`)
+    // as the dependencies have now changed, the require cache must be invalidated
+    // otherwise it may affect the behavior of the migrator
+    clearRequireCache()
 
     // The cached `pkg` field won't automatically update after running `this.pm.upgrade`.
     // Also, `npm install pkg@~version` won't replace the original `"pkg": "^version"` field.
     // So we have to manually update `this.pkg` and write to the file system in `runMigrator`
     this.pkg[depEntry][packageName] = `~${targetVersion}`
     const noop = () => {}
+
     const pluginMigrator =
       loadModule(`${packageName}/migrator`, this.context) || noop