There was code to support set literals (on Python 2.7 and newer), but it
was buggy: SAFE_NODES.union() doesn't modify SAFE_NODES in place,
instead it returns a new set object that is then silently discarded.
I added a unit test and fixed the code. I also changed the version
check to use sys.version_tuple instead of a string comparison, for
consistency with the subsequent Python 3.4 version check that I added in
the previous commit.
Two things changed in Python 3.4:
- 'basestring' is no longer defined, so use six.string_types
- True/False are now special AST node types (NamedConstant) rather than
just names
(Good thing we had tests, or I wouldn't have noticed the 2nd thing!)
I found only one place where safe_eval() is called inside the ansible
codebase: in lib/template/__init__.py. The call to safe_eval(result,
...) is protected by result.startswith('...'), which means result cannot
possibly be a byte string on Python 3 (or startswith() would raise, so
six.string_types (which excludes byte strings on Python 3) is fine here.
