(core) Fix bug with renaming when a formula uses a local name for a user table.

Summary:
When a formula used a local variable referring to a user table (which is
a global name), e.g. `myvar = MyTable; myvar.lookupOne(...)`, renaming
logic mistakenly used the inferred name (`MyTable`) in places where the
actual variable name (`myvar`) should have been used.

Additionally, we should not rename local variables, even if they match a
global name.

This fixes both issues.

Test Plan: Added a test case that checks that local variables aren't renamed.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D3846

sandbox/grist/codebuilder.py

@@ -195,6 +195,11 @@ def _is_table(node):
   return (isinstance(node, astroid.nodes.ClassDef) and node.decorators and
           node.decorators.nodes[0].as_string() == 'grist.UserTable')
 
+def _is_local(node):
+  """
+  Returns true if node is a Name node for an innermost variable.
+  """
+  return isinstance(node, astroid.nodes.Name) and node.name in node.scope().locals
 
 
 @contextlib.contextmanager
@@ -394,14 +399,15 @@ def parse_grist_names(builder):
     in_text, in_value, in_patch = patch_source
     if in_value:
       return (in_value, in_patch.start, table_id, col_id)
+    return None
 
   parsed_names = []
   for node in asttokens.util.walk(atok.tree):
     if isinstance(node, astroid.nodes.Name):
       obj = infer(node)
-      if _is_table(obj):
+      if _is_table(obj) and not _is_local(node):
         start, end = atok.get_text_range(node)
-        parsed_names.append(make_tuple(start, end, obj.name, None))
+        parsed_names.append(make_tuple(start, end, node.name, None))
 
     elif isinstance(node, astroid.nodes.Attribute):
       obj = infer(node.expr)
@@ -431,7 +437,7 @@ def save_to_linecache(source_code):
   Makes source code available to friendly-traceback and traceback formatting in general.
   """
   if six.PY3:
-    import friendly_traceback.source_cache
+    import friendly_traceback.source_cache    # pylint: disable=import-error
 
     friendly_traceback.source_cache.cache.add(code_filename, source_code)
   else:

sandbox/grist/test_renames2.py

@@ -395,3 +395,27 @@ class TestRenames2(test_engine.EngineTestCase):
 
     self.assertTableData("People", cols="subset", data=self.people_data)
     self.assertTableData("Games", cols="subset", data=self.games_data)
+
+  def test_renames_i(self):
+    # Rename when using a local variable referring to a user table.
+    # Test also that a local variable that happens to match a global name is unaffected by renames.
+    self.modify_column("Games", "winner", formula=(
+      "myvar = Entries\n"
+      "People = Entries\n"
+      "myvar.lookupOne(game=$id, rank=1).person\n"
+      "People.lookupOne(game=$id, rank=1).person\n"
+    ))
+    self.apply_user_action(["RenameColumn", "Entries", "game", "juego"])
+    self.apply_user_action(["RenameTable", "People", "Persons"])
+
+    # Check that renames worked.
+    new_col = self.engine.docmodel.columns.lookupOne(tableId='Games', colId='winner')
+    self.assertEqual(new_col.formula, (
+      "myvar = Entries\n"
+      "People = Entries\n"
+      "myvar.lookupOne(juego=$id, rank=1).person\n"
+      "People.lookupOne(juego=$id, rank=1).person\n"
+    ))
+
+    self.assertTableData("Persons", cols="subset", data=self.people_data)
+    self.assertTableData("Games", cols="subset", data=self.games_data)