Add has_recursive_symlinks function

Author: Flamefire

easybuild/tools/filetools.py

@@ -44,6 +44,7 @@
 import hashlib
 import imp
 import inspect
+import itertools
 import os
 import re
 import shutil
@@ -2340,6 +2341,25 @@ def copy_files(paths, target_path, force_in_dry_run=False, target_single_file=Fa
         raise EasyBuildError("One or more files to copy should be specified!")
 
 
+def has_recursive_symlinks(path):
+    """
+    Check the given directory for recursive symlinks.
+
+    That means symlinks to folders inside the path which would cause infinite loops when traversed regularily.
+
+    :param path: Path to directory to check
+    """
+    for dirpath, dirnames, filenames in os.walk(path, followlinks=True):
+        for name in itertools.chain(dirnames, filenames):
+            fullpath = os.path.join(dirpath, name)
+            if os.path.islink(fullpath):
+                linkpath = os.path.realpath(fullpath)
+                fullpath += os.sep  # To catch the case where both are equal
+                if fullpath.startswith(linkpath + os.sep):
+                    return True
+    return False
+
+
 def copy_dir(path, target_path, force_in_dry_run=False, dirs_exist_ok=False, **kwargs):
     """
     Copy a directory from specified location to specified location

test/framework/filetools.py

@@ -1790,6 +1790,46 @@ def test_copy_files(self):
         regex = re.compile("^copied 2 files to .*/target")
         self.assertTrue(regex.match(stdout), "Pattern '%s' should be found in: %s" % (regex.pattern, stdout))
 
+    def test_has_recursive_symlinks(self):
+        """Test has_recursive_symlinks function"""
+        test_folder = tempfile.mkdtemp()
+        self.assertFalse(ft.has_recursive_symlinks(test_folder))
+        # Clasic Loop: Symlink to .
+        os.symlink('.', os.path.join(test_folder, 'self_link_dot'))
+        self.assertTrue(ft.has_recursive_symlinks(test_folder))
+        # Symlink to self
+        test_folder = tempfile.mkdtemp()
+        os.symlink('self_link', os.path.join(test_folder, 'self_link'))
+        self.assertTrue(ft.has_recursive_symlinks(test_folder))
+        # Symlink from 2 folders up
+        test_folder = tempfile.mkdtemp()
+        sub_folder = os.path.join(test_folder, 'sub1', 'sub2')
+        os.makedirs(sub_folder)
+        os.symlink(os.path.join('..', '..'), os.path.join(sub_folder, 'uplink'))
+        self.assertTrue(ft.has_recursive_symlinks(test_folder))
+        # Non-issue: Symlink to sibling folders
+        test_folder = tempfile.mkdtemp()
+        sub_folder = os.path.join(test_folder, 'sub1', 'sub2')
+        os.makedirs(sub_folder)
+        sibling_folder = os.path.join(test_folder, 'sub1', 'sibling')
+        os.mkdir(sibling_folder)
+        os.symlink('sibling', os.path.join(test_folder, 'sub1', 'sibling_link'))
+        os.symlink(os.path.join('..', 'sibling'), os.path.join(test_folder, sub_folder, 'sibling_link'))
+        self.assertFalse(ft.has_recursive_symlinks(test_folder))
+        # Tricky case: Sibling symlink to folder starting with the same name
+        os.mkdir(os.path.join(test_folder, 'sub11'))
+        os.symlink(os.path.join('..', 'sub11'), os.path.join(test_folder, 'sub1', 'trick_link'))
+        self.assertFalse(ft.has_recursive_symlinks(test_folder))
+        # Symlink cycle: sub1/cycle_2 -> sub2, sub2/cycle_1 -> sub1, ...
+        test_folder = tempfile.mkdtemp()
+        sub_folder1 = os.path.join(test_folder, 'sub1')
+        sub_folder2 = sub_folder = os.path.join(test_folder, 'sub2')
+        os.mkdir(sub_folder1)
+        os.mkdir(sub_folder2)
+        os.symlink(os.path.join('..', 'sub2'), os.path.join(sub_folder1, 'cycle_1'))
+        os.symlink(os.path.join('..', 'sub1'), os.path.join(sub_folder2, 'cycle_2'))
+        self.assertTrue(ft.has_recursive_symlinks(test_folder))
+
     def test_copy_dir(self):
         """Test copy_dir function."""
         testdir = os.path.dirname(os.path.abspath(__file__))