Add exceptions in the upgrading command to warn about the requirement to run it on 2.x (nelmio#1501)

Author: GuilhemN

README.md

@@ -12,7 +12,7 @@ for your APIs.
 
 ## Migrate from 2.x to 3.0
 
-[To migrate from 2.x to 3.0, just follow our guide.](https://github.com/nelmio/NelmioApiDocBundle/blob/master/UPGRADE-3.0.md)
+[To migrate from 2.x to 3.0, follow our guide.](https://github.com/nelmio/NelmioApiDocBundle/blob/master/UPGRADE-3.0.md)
 
 ## Installation
 

UPGRADE-3.0.md

@@ -44,6 +44,14 @@ class SwaggerDocblockConvertCommand extends ContainerAwareCommand
     {
         $views = explode(',', $input->getOption('views'));
 
+        if (!$this->getContainer()->has('nelmio_api_doc.extractor.api_doc_extractor')) {
+            if (!$this->getContainer()->has('nelmio_api_doc.controller.swagger_ui')) {
+                throw new \RuntimeException('NelmioApiDocBundle is not installed. Please run `composer require nelmio/api-doc-bundle`.');
+            } else {
+                throw new \RuntimeException('This command only works with NelmioApiDocBundle 2.x installed while version 3.x is currently installed. Please downgrade to 2.x to execute this command and bump your constraint only after its execution.');                      
+            }
+        }
+
         $extractor = $this->getContainer()->get('nelmio_api_doc.extractor.api_doc_extractor');
 
         $apiDocs = [];