Check for recursive symlinks by default before copying a folder

Avoids endless loops and creating infinite length paths when
`symlinks=True` is NOT also passed to copy_dir

Author: Flamefire

easybuild/tools/filetools.py

@@ -2356,18 +2356,21 @@ def has_recursive_symlinks(path):
                 linkpath = os.path.realpath(fullpath)
                 fullpath += os.sep  # To catch the case where both are equal
                 if fullpath.startswith(linkpath + os.sep):
+                    _log.info("Recursive symlink detected at %s", fullpath)
                     return True
     return False
 
 
-def copy_dir(path, target_path, force_in_dry_run=False, dirs_exist_ok=False, **kwargs):
+def copy_dir(path, target_path, force_in_dry_run=False, dirs_exist_ok=False, check_for_recursive_symlinks=True,
+             **kwargs):
     """
     Copy a directory from specified location to specified location
 
     :param path: the original directory path
     :param target_path: path to copy the directory to
     :param force_in_dry_run: force running the command during dry run
     :param dirs_exist_ok: boolean indicating whether it's OK if the target directory already exists
+    :param check_for_recursive_symlinks: If symlink arg is not given or False check for recursive symlinks first
 
     shutil.copytree is used if the target path does not exist yet;
     if the target path already exists, the 'copy' function will be used to copy the contents of
@@ -2379,6 +2382,13 @@ def copy_dir(path, target_path, force_in_dry_run=False, dirs_exist_ok=False, **k
         dry_run_msg("copied directory %s to %s" % (path, target_path))
     else:
         try:
+            if check_for_recursive_symlinks and not kwargs.get('symlinks'):
+                if has_recursive_symlinks(path):
+                    raise EasyBuildError("Recursive symlinks detected in %s. "
+                                         "Will not try copying this unless `symlinks=True` is passed",
+                                         path)
+                else:
+                    _log.debug("No recursive symlinks in %s", path)
             if not dirs_exist_ok and os.path.exists(target_path):
                 raise EasyBuildError("Target location %s to copy %s to already exists", target_path, path)
 
@@ -2406,7 +2416,9 @@ def copy_dir(path, target_path, force_in_dry_run=False, dirs_exist_ok=False, **k
                 paths_to_copy = [os.path.join(path, x) for x in entries]
 
                 copy(paths_to_copy, target_path,
-                     force_in_dry_run=force_in_dry_run, dirs_exist_ok=dirs_exist_ok, **kwargs)
+                     force_in_dry_run=force_in_dry_run, dirs_exist_ok=dirs_exist_ok,
+                     check_for_recursive_symlinks=False,  # Don't check again
+                     **kwargs)
 
             else:
                 # if dirs_exist_ok is not enabled or target directory doesn't exist, just use shutil.copytree

test/framework/filetools.py

@@ -1901,6 +1901,15 @@ def ignore_func(_, names):
         ft.mkdir(subdir)
         ft.copy_dir(srcdir, target_dir, symlinks=True, dirs_exist_ok=True)
 
+        # Detect recursive symlinks by default instead of infinite loop during copy
+        ft.remove_dir(target_dir)
+        os.symlink('.', os.path.join(subdir, 'recursive_link'))
+        self.assertErrorRegex(EasyBuildError, 'Recursive symlinks detected', ft.copy_dir, srcdir, target_dir)
+        self.assertFalse(os.path.exists(target_dir))
+        # Ok for symlinks=True
+        ft.copy_dir(srcdir, target_dir, symlinks=True)
+        self.assertTrue(os.path.exists(target_dir))
+
         # also test behaviour of copy_file under --dry-run
         build_options = {
             'extended_dry_run': True,