Add dns.rdata.load_all_types(). (#1095)

dns/rdata.py

@@ -646,13 +646,14 @@ def from_wire_parser(cls, rdclass, rdtype, parser, origin=None):
  {}
 )
 _module_prefix = "dns.rdtypes"
+_dynamic_load_allowed = True
 
 
-def get_rdata_class(rdclass, rdtype):
+def get_rdata_class(rdclass, rdtype, use_generic=True):
  cls = _rdata_classes.get((rdclass, rdtype))
  if not cls:
  cls = _rdata_classes.get((dns.rdatatype.ANY, rdtype))
- if not cls:
+ if not cls and _dynamic_load_allowed:
  rdclass_text = dns.rdataclass.to_text(rdclass)
  rdtype_text = dns.rdatatype.to_text(rdtype)
  rdtype_text = rdtype_text.replace("-", "_")
@@ -670,12 +671,36 @@ def get_rdata_class(rdclass, rdtype):
  _rdata_classes[(rdclass, rdtype)] = cls
  except ImportError:
  pass
- if not cls:
+ if not cls and use_generic:
  cls = GenericRdata
  _rdata_classes[(rdclass, rdtype)] = cls
  return cls
 
 
+def load_all_types(disable_dynamic_load=True):
+ """Load all rdata types for which dnspython has a non-generic implementation.
+
+ Normally dnspython loads DNS rdatatype implementations on demand, but in some
+ specialized cases loading all types at an application-controlled time is preferred.
+
+ If *disable_dynamic_load*, a ``bool``, is ``True`` then dnspython will not attempt
+ to use its dynamic loading mechanism if an unknown type is subsequently encountered,
+ and will simply use the ``GenericRdata`` class.
+ """
+ # Load class IN and ANY types.
+ for rdtype in dns.rdatatype.RdataType:
+ get_rdata_class(dns.rdataclass.IN, rdtype, False)
+ # Load the one non-ANY implementation we have in CH. Everything
+ # else in CH is an ANY type, and we'll discover those on demand but won't
+ # have to import anything.
+ get_rdata_class(dns.rdataclass.CH, dns.rdatatype.A, False)
+ if disable_dynamic_load:
+ # Now disable dynamic loading so any subsequent unknown type immediately becomes
+ # GenericRdata without a load attempt.
+ global _dynamic_load_allowed
+ _dynamic_load_allowed = False
+
+
 def from_text(
  rdclass: Union[dns.rdataclass.RdataClass, str],
  rdtype: Union[dns.rdatatype.RdataType, str],

doc/rdata-make.rst

@@ -6,3 +6,9 @@ Making DNS Rdata
 .. autofunction:: dns.rdata.from_text
 .. autofunction:: dns.rdata.from_wire_parser
 .. autofunction:: dns.rdata.from_wire
+
+Miscellaneous Rdata Functions
+-----------------------------
+
+.. autofunction:: dns.rdata.register_type
+.. autofunction:: dns.rdata.load_all_types