tabstops can be overwritten from interpolation

It adds new type of flexibility, where just entered text can be
dynamically modified if some conditions are satisfied (e.g. dynamically
add line wraps).

pythonx/UltiSnips/text_objects/_python_code.py

@@ -28,6 +28,14 @@ class _Tabs(object):
             return ''
         return ts.current_text
 
+    def __setitem__(self, no, value):
+        ts = self._to._get_tabstop(
+            self._to,
+            int(no))  # pylint:disable=protected-access
+        if ts is None:
+            return
+        ts.overwrite(value)
+
 _VisualContent = namedtuple('_VisualContent', ['mode', 'text'])
 
 

test/test_Interpolation.py

@@ -429,6 +429,17 @@ class PythonCode_AccessKilledTabstop_OverwriteFirst(_VimTest):
     keys = 'test' + EX + 'aaa'
     wanted = 'aaa'
 
+class PythonCode_CanOverwriteTabstop(_VimTest):
+    snippets = (
+        'test',
+        """$1`!p if len(t[1]) > 3 and len(t[2]) == 0:
+            t[2] = t[1][2:];
+            t[1] = t[1][:2] + '-\\n\\t';
+            vim.command('call feedkeys("\<End>", "n")');
+            `$2""")
+    keys = 'test' + EX + 'blah' + ', bah'
+    wanted = "bl-\n\tah, bah"
+
 
 class PythonVisual_NoVisualSelection_Ignore(_VimTest):
     snippets = ('test', 'h`!p snip.rv = snip.v.mode + snip.v.text`b')