Noissue - Fixed false positive A203 when using "yield from"

flake8-eyeo/flake8_eyeo.py

 # This file is part of Adblock Plus <https://adblockplus.org/>,
 # Copyright (C) 2006-present eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ skipping 84 matching lines @@
                 self.errors.append((node, 'A202 dead code after '
                                           '{}'.format(statement)))
 
             if isinstance(node, LEAVE_BLOCK):
                 leave_node = node
 
             if can_have_unused_expr or not isinstance(node, ast.Expr):
                 continue
             if docstring and i == 0 and isinstance(node.value, ast.Str):
                 continue
-            if isinstance(node.value, (ast.Call, ast.Yield)):
+
+            non_literal_expr_nodes = (ast.Call, ast.Yield)
+            try:
+                non_literal_expr_nodes += (ast.YieldFrom,)

[Sebastian Noack, 2017/11/29 21:51:37]

This change prevents and A203 to be (incorrectly) reported for code like this:

  def foo(x):
      yield from x

"yield from" was introduced in Python 3.3, hence the check here. Also I didn't
add a regression test, since we currently cannot have test cases that cause
syntax errors on some Python versions. :(

+            except AttributeError:
+                pass
+            if isinstance(node.value, non_literal_expr_nodes):
                 continue
 
             self.errors.append((node, 'A203 unused expression'))
 
         if pass_node:
             if not nodes_required or len(nodes) > 1:
                 self.errors.append((pass_node, 'A204 redundant '
                                                'pass statement'))
 
             if not block_required and not has_non_pass:
@@ skipping 350 matching lines @@
                     return [(pos, 'A111 redundant parenthesis for {} '
                                   'statement'.format(statement))]
 
     return []
 
 
 for checker in [check_ast, check_non_default_encoding,
                 check_quotes, check_redundant_parenthesis]:
     checker.name = 'eyeo'
     checker.version = __version__