Make the diff nicer if there is no ending newline, fixes #1581

jedi/api/refactoring/__init__.py

@@ -25,11 +25,33 @@ class ChangedFile(object):
     def get_diff(self):
         old_lines = split_lines(self._module_node.get_code(), keepends=True)
         new_lines = split_lines(self.get_new_code(), keepends=True)
+
+        # Add a newline at the end if it's missing. Otherwise the diff will be
+        # very weird. A `diff -u file1 file2` would show the string:
+        #
+        #     \ No newline at end of file
+        #
+        # This is not necessary IMO, because Jedi does not really play with
+        # newlines and the ending newline does not really matter in Python
+        # files. ~dave
+        if old_lines[-1] != '':
+            old_lines[-1] += '\n'
+        if new_lines[-1] != '':
+            new_lines[-1] += '\n'
+
         project_path = self._inference_state.project._path
+        if self._from_path is None:
+            from_p = ''
+        else:
+            from_p = relpath(self._from_path, project_path)
+        if self._to_path is None:
+            to_p = ''
+        else:
+            to_p = relpath(self._to_path, project_path)
         diff = difflib.unified_diff(
             old_lines, new_lines,
-            fromfile=relpath(self._from_path, project_path),
-            tofile=relpath(self._to_path, project_path),
+            fromfile=from_p,
+            tofile=to_p,
         )
         # Apparently there's a space at the end of the diff - for whatever
         # reason.

test/test_api/test_refactoring.py

@@ -62,3 +62,17 @@ def test_rename_none_path(Script):
     with pytest.raises(jedi.RefactoringError, match='on a Script with path=None'):
         refactoring.apply()
     assert refactoring
+
+
+def test_diff_without_ending_newline(Script):
+    refactoring = Script('a = 1\nb\na').rename(1, 0, new_name='c')
+    assert refactoring.get_diff() == dedent('''\
+        --- 
+        +++ 
+        @@ -1,3 +1,3 @@
+        -a = 1
+        +c = 1
+         b
+        -a
+        +c
+        ''')