Fix handling recursive symlinks

When pytest was run on a directory containing a recursive symlink it failed
with ELOOP as the library was not able to determine the type of the
direntry:

src/_pytest/main.py:685: in collect
    if not direntry.is_file():
E   OSError: [Errno 40] Too many levels of symbolic links: '/home/florian/proj/pytest/tests/recursive'

This is fixed now by handling ELOOP.

Fixes pytest-dev#7951

src/_pytest/main.py

@@ -5,6 +5,7 @@
 import importlib
 import os
 import sys
+import errno
 from pathlib import Path
 from typing import Callable
 from typing import Dict
@@ -676,8 +677,14 @@ def collect(self) -> Iterator[Union[nodes.Item, nodes.Collector]]:
 
                 seen_dirs: Set[py.path.local] = set()
                 for direntry in visit(str(argpath), self._recurse):
-                    if not direntry.is_file():
-                        continue
+                    try:
+                        if not direntry.is_file():
+                            continue
+                    except OSError as err:
+                        if err.errno == errno.ELOOP:
+                            continue
+                        else:
+                            raise
 
                     path = py.path.local(direntry.path)
                     dirpath = path.dirpath()

testing/test_collection.py

@@ -1404,3 +1404,17 @@ def a(): return 4
     result = testdir.runpytest()
     # Not INTERNAL_ERROR
     assert result.ret == ExitCode.INTERRUPTED
+
+
+def test_does_not_crash_on_recursive_symlink(testdir: Testdir) -> None:
+    """Regression test for an issue around recursive symlinks (#7951)."""
+    testdir.makepyfile(
+        """
+        def test_foo(): assert True
+        """
+    )
+    os.symlink("recursive", str(testdir.tmpdir.join("recursive")))
+    result = testdir.runpytest()
+
+    assert result.ret == ExitCode.OK
+    assert result.parseoutcomes() == {"passed": 1}