Validate LocalToField offsets during construction

CHANGELOG.md

@@ -1,5 +1,6 @@
 # **Upcoming release**
 
+- #927 Validate convert local variable to field eligibility in the constructor. (@Narek-Khachikyan)
 - #895 patchedast Starred and keyword now consumes their syntactically expected and ** (@lieryan)
 - #896 patchedast cleanup and refactoring (@lieryan)
 - #905 Ignore `node_modules` directories by default when scanning project files and source folders. (@marcoeangeli)

rope/refactor/localtofield.py

@@ -8,17 +8,17 @@ def __init__(self, project, resource, offset):
         self.resource = resource
         self.offset = offset
 
-    def get_changes(self):
-        name = worder.get_name_at(self.resource, self.offset)
         this_pymodule = self.project.get_pymodule(self.resource)
-        pyname = evaluate.eval_location(this_pymodule, self.offset)
-        if not self._is_a_method_local(pyname):
+        self.pyname = evaluate.eval_location(this_pymodule, self.offset)
+        if not self._is_a_method_local(self.pyname):
             raise exceptions.RefactoringError(
                 "Convert local variable to field should be performed on "
                 "a local variable of a method."
             )
 
-        pymodule, lineno = pyname.get_definition_location()
+    def get_changes(self):
+        name = worder.get_name_at(self.resource, self.offset)
+        pymodule, lineno = self.pyname.get_definition_location()
         function_scope = pymodule.get_scope().get_inner_scope_for_line(lineno)
         # Not checking redefinition
         # self._check_redefinition(name, function_scope)
@@ -40,12 +40,13 @@ def _get_field_name(self, pyfunction, name):
         return new_name
 
     def _is_a_method_local(self, pyname):
+        if not isinstance(pyname, pynames.AssignedName):
+            return False
         pymodule, lineno = pyname.get_definition_location()
         holding_scope = pymodule.get_scope().get_inner_scope_for_line(lineno)
         parent = holding_scope.parent
         return (
-            isinstance(pyname, pynames.AssignedName)
-            and pyname in holding_scope.get_names().values()
+            pyname in holding_scope.get_names().values()
             and holding_scope.get_kind() == "Function"
             and parent is not None
             and parent.get_kind() == "Class"

ropetest/refactor/__init__.py

@@ -877,11 +877,11 @@ def a_func(self):
         self.assertEqual(expected, self.mod.read())
 
     def test_raising_exception_when_performed_on_a_global_var(self):
-        self.mod.write("var = 10\n")
+        self.mod.write(dedent("""\
+            var = 10
+        """))
         with self.assertRaises(RefactoringError):
-            self._perform_convert_local_variable_to_field(
-                self.mod, self.mod.read().index("var") + 1
-            )
+            LocalToField(self.project, self.mod, 0)
 
     def test_raising_exception_when_performed_on_field(self):
         code = dedent("""\
@@ -891,9 +891,7 @@ def a_func(self):
         """)
         self.mod.write(code)
         with self.assertRaises(RefactoringError):
-            self._perform_convert_local_variable_to_field(
-                self.mod, self.mod.read().index("var") + 1
-            )
+            LocalToField(self.project, self.mod, code.index("var") + 1)
 
     def test_raising_exception_when_performed_on_a_parameter(self):
         code = dedent("""\
@@ -903,9 +901,45 @@ def a_func(self, var):
         """)
         self.mod.write(code)
         with self.assertRaises(RefactoringError):
-            self._perform_convert_local_variable_to_field(
-                self.mod, self.mod.read().index("var") + 1
-            )
+            LocalToField(self.project, self.mod, code.index("var") + 1)
+
+    def test_raising_exception_when_performed_on_a_function_local(self):
+        code = dedent("""\
+            def a_func():
+                var = 10
+        """)
+        self.mod.write(code)
+        with self.assertRaises(RefactoringError):
+            LocalToField(self.project, self.mod, code.index("var"))
+
+    def test_raising_exception_when_performed_on_a_class_variable(self):
+        code = dedent("""\
+            class A:
+                var = 10
+        """)
+        self.mod.write(code)
+        with self.assertRaises(RefactoringError):
+            LocalToField(self.project, self.mod, code.index("var"))
+
+    def test_raising_exception_when_performed_on_an_unresolved_name(self):
+        code = dedent("""\
+            class A:
+                def a_func(self):
+                    missing
+        """)
+        self.mod.write(code)
+        with self.assertRaises(RefactoringError):
+            LocalToField(self.project, self.mod, code.index("missing"))
+
+    def test_raising_exception_when_performed_on_a_builtin(self):
+        code = dedent("""\
+            class A:
+                def a_func(self):
+                    len([])
+        """)
+        self.mod.write(code)
+        with self.assertRaises(RefactoringError):
+            LocalToField(self.project, self.mod, code.index("len"))
 
     # NOTE: This situation happens a lot and is normally not an error
     # @testutils.assert_raises(RefactoringError)