Reflection: Fix null as first return type

[theCapypara]

Description (*)

This fixes null as the first return type for methods used in the service layer.

The examples given in #25656 are now working. Additionally the Swagger schema generation no longer fails with the exception The "" data type isn't declared. Verify the type and try again..

If null is the only return type, a new exception will be thrown. It's not, see comments below

Fixed Issues

1. M2.3.2 : Nullable getters in Service Contracts will throw a reflection error when used in the web API  #25656: M2.3.2 : Nullable getters in Service Contracts will throw a reflection error when used in the web API

Manual testing scenarios (*)

1. Create a simple REST WebAPI endpoint, with a getter Method as described in M2.3.2 : Nullable getters in Service Contracts will throw a reflection error when used in the web API  #25656
2. Try to open the Swagger documentation (should work now)
3. Try to execute the API endpoint (should work now)

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)

[m2-assistant]

Hi @Parakoopa. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento give me test instance - deploy test instance based on PR changes
• @magento give me 2.3-develop instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Guide documentation.

[theCapypara]

I had to remove the exception I added to catch cases, where only null is defined as a return type for methods, which isn't supported by the code resolving type instances of return types.

The reason for this is, that the reflection logic also seems to be used during integration tests, and there are methods used there which actually return null. There are no errors being thrown there, so assume in those cases null is actually supported as a return type by the reflection logic. For reference, here are the logs of the integration builds:

11:34:01 [Integration-7-ce] In TypeProcessor.php line 297:
11:34:01 [Integration-7-ce]
11:34:01 [Integration-7-ce]   [InvalidArgumentException]
11:34:01 [Integration-7-ce]   No valid return type for Magento\TestModuleMysqlMq\Model\DataObjectReposito
11:34:01 [Integration-7-ce]   ry::delayedOperation() specified. Verify the return type and try again.
11:34:01 [Integration-7-ce]
11:34:01 [Integration-7-ce]
11:34:01 [Integration-7-ce] Exception trace:
11:34:01 [Integration-7-ce]  () at /var/www/html/lib/internal/Magento/Framework/Reflection/TypeProcessor.php:297
11:34:01 [Integration-7-ce]  Magento\Framework\Reflection\TypeProcessor->getGetterReturnType() at /var/www/html/lib/internal/Magento/Framework/Reflection/MethodsMap.php:173
11:34:01 [Integration-7-ce]  Magento\Framework\Reflection\MethodsMap->getMethodMapViaReflection() at /var/www/html/lib/internal/Magento/Framework/Reflection/MethodsMap.php:108
11:34:01 [Integration-7-ce]  Magento\Framework\Reflection\MethodsMap->getMethodsMap() at /var/www/html/lib/internal/Magento/Framework/Reflection/MethodsMap.php:81

This means methods that only have null as a return type will still throw the same weird exceptions mentioned in the issue (when used via webapi), but the integration tests are working again.

Methods that can return null AND a valid type are now working correctly, regardless of order.

[magento-engcom-team]

Hi @ihor-sviziev, thank you for the review.
ENGCOM-6920 has been created to process this Pull Request
✳️ @ihor-sviziev, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[engcom-Alfa]

✔️ QA Passed

[m2-assistant]

Hi @Parakoopa, thank you for your contribution!
Please, complete Contribution Survey, it will take less than a minute.
Your feedback will help us to improve contribution process.