Add __bool__() / __nonzero__() method to python rpmmi objects (ticket #153)

- Objects supporting __len__() use (len > 0) for boolean representation,
  which normally makes sense but as the match iterator count is often
  zero despite the iterator actually existing and returning something,
  and breaks existing code (rpmlint at least)
- Adding a __bool__() (known as __nonzero__() in Python < 3) method
  returning true for non-NULL iterator fixes this and gives more
  meaningful answers than pre 4.8.0 which simply always returned True

1 files changed, 20 insertions, 1 deletions

diff --git a/python/rpmmi-py.c b/python/rpmmi-py.c
index f6dd80271..b7bfb1b5d 100644
--- a/python/rpmmi-py.c
+++ b/python/rpmmi-py.c
@@ -137,11 +137,30 @@ static Py_ssize_t rpmmi_length(rpmmiObject * s)
     return s->mi ? rpmdbGetIteratorCount(s->mi) : 0;
 }
 
+static int rpmmi_bool(rpmmiObject *s)
+{
+    return (s->mi != NULL);
+}
+
 PyMappingMethods rpmmi_as_mapping = {
     (lenfunc) rpmmi_length,		/* mp_length */
     0,
 };
 
+static PyNumberMethods rpmmi_as_number = {
+	0, /* nb_add */
+	0, /* nb_subtract */
+	0, /* nb_multiply */
+	0, /* nb_divide */
+	0, /* nb_remainder */
+	0, /* nb_divmod */
+	0, /* nb_power */
+	0, /* nb_negative */
+	0, /* nb_positive */
+	0, /* nb_absolute */
+	(inquiry)rpmmi_bool, /* nb_bool/nonzero */
+};
+
 static char rpmmi_doc[] =
 "";
 
@@ -156,7 +175,7 @@ PyTypeObject rpmmi_Type = {
 	0,				/* tp_setattr */
 	0,				/* tp_compare */
 	0,				/* tp_repr */
-	0,				/* tp_as_number */
+	&rpmmi_as_number,		/* tp_as_number */
 	0,				/* tp_as_sequence */
 	&rpmmi_as_mapping,		/* tp_as_mapping */
 	0,				/* tp_hash */