Magento 2.3 upgrade failed with PHP Fatal error: Uncaught Error: Class Zend\Code\Annotation\AnnotationManager Error

Question

I've upgraded my Dev server from Magento 2.2.5 to 2.3

I had to install in increments by going from 2.2.5->2.2.6>2.2.7 and then on to 2.3

There were also a few modules I had to remove to get the upgrade to work.

However, now that it's all installed, when I type php bin/magento setup:upgrade I get and error which is

PHP Fatal error:  Uncaught Error: Class 'Zend\Code\Annotation\AnnotationManager' not found in /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-di/src/Definition/IntrospectionStrategy.php:68
Stack trace:
#0 /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-di/src/Definition/IntrospectionStrategy.php(48): Zend\Di\Definition\IntrospectionStrategy->createDefaultAnnotationManager()
#1 /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-di/src/Definition/RuntimeDefinition.php(54): Zend\Di\Definition\IntrospectionStrategy->__construct()
#2 /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-di/src/Di.php(116): Zend\Di\Definition\RuntimeDefinition->__construct()
#3 /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-mvc/src/Service/DiFactory.php(43): Zend\Di\Di->__construct()
#4 /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-mvc/src/Service/DiFactory.php(63): Zend\Mvc\Service\D in /chroot/home/a7669e95/mydomain.com/html/vendor/zendframework/zend-di/src/Definition/IntrospectionStrategy.php on line 68

I've substituted my dev domain for mydomain.com in the above.

Anybody got any ideas on what would cause this or more importantly, how I fix it?

Answer 1

Check the "minimum-stability" in your composer.json, in case it is not set to stable you migth be requiring an incorrect zenframework/zend-code version instead of the 3.3.1 that Magento 2.3.1 is expecting.