[C++-sig] Boost.python suggestion + pyste bug

[Niall Douglas]

It's taken me a few hours, but I've finally found the cause of the 
mysterious "AttributeError: can't set attribute" error I kept getting 
when I imported my wrapper dll.

If you replace line 29 to 32 in errors.cpp with:

    catch(const boost::python::error_already_set&)
    {
        // The python error reporting has already been handled.
		PyErr_SetString(PyExc_RuntimeError, "Boost.python API wrapped more 
than once");
    }

Then you'll get a much nicer and useful error message. I appreciate 
that the comment implies it's already been handled, but I'm 
definitely getting "AttributeError: can't set attribute" here which 
is really not useful.

Oh Nicodemus! Pyste is generating multiple def()'s with the same name 
where it doesn't need them. Here's what's happening: if A inherits B 
which inherits C and each of A, B & C provide a method called 
"metaClass", then when wrapping A only pyste currently adds a 
.def("metaClass", &X::metaClass) where X is A,B,C ie; it adds one for 
B & C too where under C++ inheritance rules B::metaClass() and 
C::metaClass() disappear. It shouldn't add the B::metaClass() nor 
C::metaClass().

A similar problem exists where A, B & C all define a class (let's 
call it FXMapEntry). Once again pyste writes out class definitions 
for each and every FXMapEntry for each of A, B & C where really it 
should only do so for A::FXMapEntry.

And lastly, the other similar problem is for enum's. If A, B & C all 
define an enum where C::ID_LAST is B::ID_FIRST and B::ID_LAST is 
A::ID_FIRST etc. then pyste defines all the ID_LAST's and ID_FIRST's 
(and thus causing a runtime error). It should in this case only 
define those items defined in the most derived class.

Speaking of enum's, multiple anonymous enum's (which pyste generates 
as _enum<int, "unnamed">) cause boost.python to die because it likes 
every enum's first parameter to be a unique type (couldn't we change 
this behaviour for simple types?). I worked around this by having 
pyste specify a "UniqueInt<n>" where n is a globally incremented 
counter. The definition of UniqueInt is:

template<int num> struct UniqueInt { int v; enum { value=num }; 
UniqueInt(int _v) : v(_v) { } operator int() const { return v; } };

Lastly, am I right in thinking that pyste currently does not use 
boost.python's ability to represent C++ class inheritance trees the 
same in python classes? I'm thinking that if you were to add support 
for this, it kinda works with the fixes necessary for fixing the bugs 
above.

Cheers,
Niall