golang_str: Fix bstr.tp_print(flags=print_repr)

On py2 objects are printed via their .tp_repr slot with flags=0
(contrary to Py_PRINT_RAW which requests to print str -
https://docs.python.org/2.7/c-api/object.html#c.PyObject_Print)

We were not handling repr'ing inside our tp_print implementation, and
as the result e.g. b('мир') was printed on interactive console as
'\xd0\xbc\xd0\xb8\xd1\x80' instead of b('мир').

Fix it.

golang/_golang_str.pyx

@@ -542,11 +542,22 @@ IF PY2:
         ctypedef int (*printfunc)(PyObject *, FILE *, int) except -1
         ctypedef struct _PyTypeObject_Print "PyTypeObject":
             printfunc tp_print
+        int Py_PRINT_RAW
+
+    cdef int _pybstr_tp_print(PyObject *obj, FILE *f, int flags) except -1:
+        o = <object>obj
+        if flags & Py_PRINT_RAW:
+            # emit str of the object instead of repr
+            # https://docs.python.org/2.7/c-api/object.html#c.PyObject_Print
+            pass
+        else:
+            # emit repr
+            o = repr(o)
 
-    cdef int _pybstr_tp_print(PyObject *obj, FILE *f, int nesting) except -1:
-        o = <bytes>obj
+        assert isinstance(o, bytes)
+        o = <bytes>o
         o = bytes(buffer(o))  # change tp_type to bytes instead of pybstr
-        return (<_PyTypeObject_Print*>Py_TYPE(o)) .tp_print(<PyObject*>o, f, nesting)
+        return (<_PyTypeObject_Print*>Py_TYPE(o)) .tp_print(<PyObject*>o, f, Py_PRINT_RAW)
 
     (<_PyTypeObject_Print*>Py_TYPE(pybstr())) .tp_print = _pybstr_tp_print
 

golang/testprog/golang_test_str.py

@@ -38,6 +38,11 @@ def main():
     print("print(repr(b)):", repr(sb))
     print("print(repr(u)):", repr(su))
 
+    # py2: print(dict) calls PyObject_Print(flags=0) for both keys and values,
+    #      not with flags=Py_PRINT_RAW used by default almost everywhere else.
+    #      this way we can verify whether bstr.tp_print handles flags correctly.
+    print("print({b: u}):", {sb: su})
+
 
 if __name__ == '__main__':
     main()

golang/testprog/golang_test_str.txt

@@ -4,3 +4,4 @@ print(qq(b)): "привет b"
 print(qq(u)): "привет u"
 print(repr(b)): b('привет b')
 print(repr(u)): u('привет u')
+print({b: u}): {b('привет b'): u('привет u')}