The autoloader throws an exception on class_exists

[sidolov]

Summary (*)

The autoloader throws an exception on class_exists. That is clearly an unexpected behavior according to the documentation: http://php.net/manual/en/function.class-exists.php

This will cause issues when including third-party libraries that are not written for Magento.

An autoloader that throws an exception is not PSR-4 compliant

Examples (*)

Run class_exists('FooFactory'). It should return false but an error is thrown instead.

To reproduce the issue apply changes from the #14085

Expected result: there is no error thrown
Actual result: autoloader throws an exception

@Vinai, @kandy, @orlangur I moved content from the #14085 to current issue.

Proposed solution

[magento-engcom-team]

Hi @sidolov. Thank you for your report.
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Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento-engcom-team give me 2.3-develop instance - upcoming 2.3.x release

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@sidolov do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[magento-engcom-team]

Hi @engcom-backlog-nazar. Thank you for working on this issue.
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[magento-engcom-team]

@engcom-backlog-nazar Thank you for verifying the issue. Based on the provided information internal tickets MAGETWO-97979, MAGETWO-97980 were created

Issue Available: @engcom-backlog-nazar, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.