From beb8c1add0facf57d70d986812ffb45336b6b261 Mon Sep 17 00:00:00 2001
From: Mario Corchero <mcorcherojim@bloomberg.net>
Date: Mon, 14 May 2018 11:20:45 -0400
Subject: [PATCH 1/2] Fix import of symlinks outside of path

Makes load_module_from_file able to import files within the path that
are just a symlink to a file outside of the path.
modutils is using realpath at the moment which will resolve the symlink
and don't allow the import as the file is detected outside of the
available paths. By checking both abspath and realpath this patches add
support for such scenarios.
---
 astroid/modutils.py                | 64 ++++++++++++++++++++++++------
 astroid/tests/unittest_modutils.py | 11 +++++
 2 files changed, 63 insertions(+), 12 deletions(-)

diff --git a/astroid/modutils.py b/astroid/modutils.py
index 83d0ba74..78a55575 100644
--- a/astroid/modutils.py
+++ b/astroid/modutils.py
@@ -285,26 +285,66 @@ 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
+
+        Given "/myfile.py" is a symlink of "/a/b/c/d.py":
+        _get_relative_base_path("/myfile.py", "/dev") ->  ["c","d"]
+    """
+    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)))
diff --git a/astroid/tests/unittest_modutils.py b/astroid/tests/unittest_modutils.py
index ef3c460c..76c04eb1 100644
--- a/astroid/tests/unittest_modutils.py
+++ b/astroid/tests/unittest_modutils.py
@@ -15,6 +15,7 @@
 import sys
 import unittest
 from xml import etree
+import tempfile
 
 import astroid
 from astroid.interpreter._import import spec
@@ -110,6 +111,16 @@ def test_knownValues_modpath_from_file_2(self):
     def test_raise_modpath_from_file_Exception(self):
         self.assertRaises(Exception, modutils.modpath_from_file, '/turlututu')
 
+    def test_import_symlink_with_source_outside_of_path(self):
+        with tempfile.NamedTemporaryFile() as tmpfile:
+            linked_file_name = 'symlinked_file.py'
+            try:
+                os.symlink(tmpfile.name, linked_file_name)
+                self.assertEqual(modutils.modpath_from_file(linked_file_name),
+                                 ['symlinked_file'])
+            finally:
+                os.remove(linked_file_name)
+
 
 class LoadModuleFromPathTest(resources.SysPathSetup, unittest.TestCase):