Make DataObject extension stricter

[shochdoerfer]

Instead of accepting and returning mixed types, the extension now accepts and returns types based on the magic method documentation in the DataObject class.

[shochdoerfer]

@hostep @sprankhub could you please check if this works relatively smoothly with your codebases? Ran it against a few of our modules and did not encounter issues. Thanks!

The general idea is to increase the strictness of the phpstan checks when DataObjects are involved. The extension adheres to the types mentioned in the doc block of the respective methods plus potential default values. But that might defer in the real world :)

[hostep]

Hi @shochdoerfer, just tested this by temporarily changing my composer.json file like this:

diff --git a/composer.json b/composer.json
index d2545fd..17e7470 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
         "symfony/console": "^2.5 || ^3.0 || ^4.0"
     },
     "require-dev": {
-        "bitexpert/phpstan-magento": "^0.1.0",
+        "bitexpert/phpstan-magento": "dev-feature/strict_dataobject",
         "ergebnis/composer-normalize": "^2.2",
         "friendsofphp/php-cs-fixer": "^2.15",
         "magento/magento-coding-standard": "^5.0",
@@ -46,6 +46,10 @@
         {
             "type": "composer",
             "url": "https://repo.magento.com/"
+        },
+        {
+            "type": "vcs",
+            "url": "https://github.com/shochdoerfer/phpstan-magento"
         }
     ],
     "scripts": {

After testing it on https://github.com/baldwin-agency/magento2-module-url-data-integrity-checker it showed one more error:

------ -------------------------------------------------------------------
  Line   Cron/ScheduleJob.php
 ------ -------------------------------------------------------------------
  42     Call to an undefined method Magento\Framework\DataObject::save().
 ------ -------------------------------------------------------------------


 [ERROR] Found 1 error

I could fix that one with the following commit: baldwin-agency/magento2-module-url-data-integrity-checker@faa683c

I think it's a good addition.

[shochdoerfer]

@hostep I wonder why this error came up. I don't think this is part of this PR, maybe due to an update of phpstan or something.

[hostep]

It's definitely caused by this PR, since I don't need the fix on version 0.2.0 of bitexpert/phpstan-magento and nothing else got updated.

And I think it makes sense because the getNewEmptyItem method defines DataObject as its return type and phpstan can't infer a specific datatype from it automatically. Right?

[sprankhub]

Just tested this. The new issues I get through this seem to be caused by the phpstan/phpstan update from 0.12.19 to 0.12.25. Hence, all good from my side. Thanks for your work!