Message11041

This one boils down to the following code snippet in PyString.java:

// Not a tuple, but possibly still some kind of container: use special argIndex values.
            argIndex = -1;
            if (args instanceof AbstractDict
                    || (!(args instanceof PySequence) && args.__findattr__("__getitem__") != null)) {
                dict = args;
                argIndex = -3;
            }

Here

args.__findattr__("__getitem__")

is used for mapping-detection. A possible solution would be to change it into

args.object___findattr__("__getitem__")

I don't think this fix would break anything. Overriding __getattr__ to sneak in a custom __getitem__ sounds insane. And it doesn't look like CPython would fall for this kind of manipulation in %-string-format-sense.

This fix also passes regrtests. So far it looks good to me. Opinions?