I see that the weird issue with DIR and Xdebug issue has been addressed, but am still confused.
Using php v7.3 and Xdebug v3.0.4, I'm having a problem with a plugin that doesn't seem to be finding some Composer-managed dependencies in my Docker dev container and am hoping to use Xdebug to trace the issue.
However:
file_exists( __DIR__ . '/autoload-classmap.php')is evaluating to false- because 
__DIR__ == "xdebug:" - and of course 
false == is_dir(__DIR__). 
In the Xdebug functions docs, it suggests ignoring a particular directory:
xdebug_set_filter( XDEBUG_FILTER_TRACING, XDEBUG_PATH_EXCLUDE, [ __DIR__ . "/some/Dir" ] );
But __DIR__ isn't a directory (evaluates as xdebug:). Where in the codebase is this filter supposed to go. Where is it that __DIR__ is still a directory?
Would it be added to the configuration in the IDE somehow? I'm using VS Code.