Fix symlink loop detection to allow shared symlink targets

docs/releases.rst

@@ -5,6 +5,16 @@
 ======================
 
 
+fmf-1.8.0
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The symlink loop detection has been improved to correctly handle
+multiple symlinks pointing to the same target directory. Previously,
+only the first symlink was followed while subsequent ones were
+incorrectly skipped as loops. The detection now tracks ancestor
+directories per branch instead of globally across the whole tree.
+
+
 fmf-1.7.0
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

fmf/base.py

@@ -104,12 +104,11 @@ def __init__(self, data, name=None, parent=None):
         # Special directives
         self._directives = dict()
 
-        # Store symlinks in while walking tree in grow() to detect
-        # symlink loops
+        # Track real paths of ancestor directories to detect symlink loops
         if parent is None:
-            self._symlinkdirs = []
+            self._realpaths = set()
         else:
-            self._symlinkdirs = parent._symlinkdirs
+            self._realpaths = set(parent._realpaths)
 
         # Special handling for top parent
         if self.parent is None:
@@ -710,6 +709,7 @@ def grow(self, path):
         if path in IGNORED_DIRECTORIES:  # pragma: no cover
             log.debug("Ignoring '{0}' (special directory).".format(path))
             return
+        self._realpaths.add(os.path.realpath(path))
         log.info("Walking through directory {0}".format(
             os.path.abspath(path)))
         try:
@@ -756,16 +756,10 @@ def grow(self, path):
                 continue
             fulldir = os.path.join(dirpath, dirname)
             if os.path.islink(fulldir):
-                # According to the documentation, calling os.path.realpath
-                # with strict = True will raise OSError if a symlink loop
-                # is encountered. But it does not do that with a loop with
-                # more than one node
                 fullpath = os.path.realpath(fulldir)
-                if fullpath in self._symlinkdirs:
+                if fullpath in self._realpaths:
                     log.debug("Not entering symlink loop {}".format(fulldir))
                     continue
-                else:
-                    self._symlinkdirs.append(fullpath)
 
             # Ignore metadata subtrees
             if os.path.isdir(os.path.join(path, dirname, SUFFIX)):

tests/unit/test_base.py

@@ -575,6 +575,59 @@ def test_validation_invalid_schema(self):
         with pytest.raises(fmf.utils.JsonSchemaError):
             self.wget.find('/recursion/deep').validate('invalid')
 
+    def test_symlink_shared_target(self):
+        """
+        Multiple symlinks pointing to the same directory should all be followed
+        """
+
+        directory = tempfile.mkdtemp()
+        try:
+            Tree.init(directory)
+            common = os.path.join(directory, 'common')
+            os.mkdir(common)
+            with open(os.path.join(common, 'main.fmf'), 'w') as main:
+                main.write('execute:\n    how: tmt\n')
+            for name in ('one', 'two'):
+                subdir = os.path.join(directory, name)
+                os.mkdir(subdir)
+                with open(os.path.join(subdir, 'main.fmf'), 'w') as main:
+                    main.write(f'environment:\n    VARIABLE: {name}\n')
+                os.symlink('../common', os.path.join(subdir, 'plan'))
+
+            tree = Tree(directory)
+            one_plan = tree.find('/one/plan')
+            two_plan = tree.find('/two/plan')
+            assert one_plan is not None
+            assert two_plan is not None
+            assert one_plan.get('execute') == {'how': 'tmt'}
+            assert two_plan.get('execute') == {'how': 'tmt'}
+            assert one_plan.get('environment') == {'VARIABLE': 'one'}
+            assert two_plan.get('environment') == {'VARIABLE': 'two'}
+        finally:
+            rmtree(directory)
+
+    def test_symlink_loop(self):
+        """
+        Symlink loops should be detected and silently skipped
+        """
+
+        directory = tempfile.mkdtemp()
+        try:
+            Tree.init(directory)
+            subdir = os.path.join(directory, 'child')
+            os.mkdir(subdir)
+            with open(os.path.join(subdir, 'main.fmf'), 'w') as main:
+                main.write('key: value\n')
+            os.symlink('..', os.path.join(subdir, 'loop'))
+
+            tree = Tree(directory)
+            child = tree.find('/child')
+            assert child is not None
+            assert child.get('key') == 'value'
+            assert tree.find('/child/loop') is None
+        finally:
+            rmtree(directory)
+
 
 class TestRemote:
     """