Cache files in OptimizedDirectorySourceLocatorFactory

[staabm]

shot in the dark for the problem seen in phpstan/phpstan#13852

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This PR adds caching when called with a array of files.

Before this PR the existing caching did only work for directories.

I tried this PR on the phpunit codebase, which proofed that with this change the numer pf findSymbols calls will be reduced to the files actually changed. Unrelated files (like bootstrap files) will no longer be processed for symbols)

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this PR combined with #4576 I can see the test-suite running with php tests/vendor/bin/paratest in 38-40 seconds

[staabm]

before this PR: running time php bin/phpstan analyze on phpstan-src@63ee5de reports OptimizedDirectorySourceLocatorFactory->findSymbols beeing invoked..

• 4248x when no cache exists
• 24x when no files changed
• 24x when src/Cache/CacheItem.php file is changed

after this PR:
running time php bin/phpstan analyze reports OptimizedDirectorySourceLocatorFactory->findSymbols beeing invoked..

• 4248x when no cache exists
• 0x when no files changed
• 2x when src/Cache/CacheItem.php file is changed

I think this will fix phpstan/phpstan#13852

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looking at the windows CI builds it seems those are ~20 seconds faster compared to other currently open PRs

[phpstan-bot]

This pull request has been marked as ready for review.

[ondrejmirtes]

Yeah I think this is an obvious improvement. I also wanted to suggest to share the common code betweet createByFiles and createByDirectory which you already did.

I have an idea for improvement. createByFiles is called from a single place. I think we should add a 2nd parameter string $uniqueCacheIdentifier which will identify the entry in the cache.

That will allow us for the identifier to become the cache key. Your current approach has a downside - when a file is removed/added, the whole cache has to go. But with a stable identifier, we'll only replace the cached parts which need replacing.

[ondrejmirtes]

Thank you!