1 files changed, 49 insertions, 12 deletions
diff --git a/astroid/modutils.py b/astroid/modutils.py
index 83d0ba74..4d8dfec0 100644
--- a/astroid/modutils.py
+++ b/astroid/modutils.py
@@ -285,26 +285,63 @@ def check_modpath_has_init(path, mod_path):
     return True
 
 
+def _get_relative_base_path(filename, path_to_check):
+    """Extracts the relative mod path of the file to import from
+
+    Check if a file is within the passed in path and if so, returns the
+    relative mod path from the one passed in.
+
+    If the filename is no in path_to_check, returns None
+
+    Note this function will look for both abs and realpath of the file,
+    this allows to find the relative base path even if the file is a
+    symlink of a file in the passed in path
+
+    Examples:
+        _get_relative_base_path("/a/b/c/d.py", "/a/b") ->  ["c","d"]
+        _get_relative_base_path("/a/b/c/d.py", "/dev") ->  None
+    """
+    importable_path = None
+    path_to_check = os.path.normcase(path_to_check)
+    abs_filename = os.path.abspath(filename)
+    if os.path.normcase(abs_filename).startswith(path_to_check):
+        importable_path = abs_filename
+
+    real_filename = os.path.realpath(filename)
+    if os.path.normcase(real_filename).startswith(path_to_check):
+        importable_path = real_filename
+
+    if importable_path:
+        base_path = os.path.splitext(importable_path)[0]
+        relative_base_path = base_path[len(path_to_check):]
+        return [pkg for pkg in relative_base_path.split(os.sep) if pkg]
+
+    return None
+
+
 def modpath_from_file_with_callback(filename, extrapath=None, is_package_cb=None):
-    filename = _path_from_filename(filename)
-    filename = os.path.realpath(os.path.expanduser(filename))
-    base = os.path.splitext(filename)[0]
+    filename = os.path.expanduser(_path_from_filename(filename))
 
     if extrapath is not None:
         for path_ in six.moves.map(_canonicalize_path, extrapath):
             path = os.path.abspath(path_)
-            if path and os.path.normcase(base[:len(path)]) == os.path.normcase(path):
-                submodpath = [pkg for pkg in base[len(path):].split(os.sep)
-                              if pkg]
-                if is_package_cb(path, submodpath[:-1]):
-                    return extrapath[path_].split('.') + submodpath
+            if not path:
+                continue
+            submodpath = _get_relative_base_path(filename, path)
+            if not submodpath:
+                continue
+            if is_package_cb(path, submodpath[:-1]):
+                return extrapath[path_].split('.') + submodpath
 
     for path in six.moves.map(_canonicalize_path, sys.path):
         path = _cache_normalize_path(path)
-        if path and os.path.normcase(base).startswith(path):
-            modpath = [pkg for pkg in base[len(path):].split(os.sep) if pkg]
-            if is_package_cb(path, modpath[:-1]):
-                return modpath
+        if not path:
+            continue
+        modpath = _get_relative_base_path(filename, path)
+        if not modpath:
+            continue
+        if is_package_cb(path, modpath[:-1]):
+            return modpath
 
     raise ImportError('Unable to find module for %s in %s' % (
         filename, ', \n'.join(sys.path)))