Skip already visited files

[mihai-stancu]

This PR attempts to fix the bugs reported in:

• Infinite loop of specific file composer-unused#659
• Runs out of memory and dies after one hour on large project composer-unused#643
• No output after php warning composer-unused#612

A self-referencing file or a cyclic dependency would generate an infinite loop during parsing.

Code example:

// test.php -- name of file must match the require_once path
<?php

require_once ('test.php');

The chosen solution is that the parser should keep track of files it has already visited and skip reparsing them.

---

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests?
2. Have you lint your code locally prior to submission?

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

[mihai-stancu]

I opened this for review but left it as [wip] until I finish adding an integration test (I already added a unit test).

[mihai-stancu]

Given that the bugfix resides in the AbstracCollector it doesn't require a backwards compatibility flag, there is no valid usecase for the collector to enter an infinitely loop.

[mihai-stancu]

I have added an integration test, but the test's assertion is fairly weak -- the empty file it loads has no symbols so I assert that it collects 0 symbols. Since I can't stop the infinite loop early (?) then I can't really check for the result of the collector and make assertions there.

However, without this PR the test would fail due to the infinite loop by exhausting all allocated memory.

Do you have any better strategies to test this?

My only other idea is to use the $includeCallback again and throw an exception if I receive the same path twice.
Throwing an exception from the callback would stop the infinite loop but since the desired case doesn't expect the Exception then the test will still fail due to an unexpected exception (instead of the exhausted memory).

[mihai-stancu]

Missed a file from the commit. Please reapprove workflows.

[mihai-stancu]

@icanhazstring did you get a chance for a review on this?

[mihai-stancu]

Ping

[icanhazstring]

Hi. Sorry might have some time later that week.
Had to attend some family occasions.

[mihai-stancu]

@icanhazstring ping