make sure Resolver.nameservers is a list or str

validate if assignment of Resolver.nameservers is a list, a str (in
which case it will be converted to a list), or None

2 files changed, 22 insertions, 1 deletions

diff --git a/dns/resolver.py b/dns/resolver.py
index c49598f..2ed0ebc 100644
--- a/dns/resolver.py
+++ b/dns/resolver.py
@@ -1079,6 +1079,27 @@ class Resolver(object):
 
         self.flags = flags
 
+    @property
+    def nameservers(self):
+        return self._nameservers
+
+    @nameservers.setter
+    def nameservers(self, nameservers):
+        """
+        :param nameservers: can be a ``str``, ``list``, or None.
+        If it's a ``str``, it will converted to a list.
+        :raise ValueError: if `nameservers` is anything other than \
+        ``str``, ``list``, or None.
+        """
+        if isinstance(nameservers, str):
+            self._nameservers = [nameservers]
+        elif isinstance(nameservers, list):
+            self._nameservers = nameservers
+        elif nameservers is None:
+            self._nameservers = None
+        else:
+            raise ValueError('nameservers must be either a str, a list, or None'
+                             ' (not a {})'.format(type(nameservers)))
 
 #: The default resolver.
 default_resolver = None
diff --git a/dns/resolver.pyi b/dns/resolver.pyi
index 06742fe..c68d04a 100644
--- a/dns/resolver.pyi
+++ b/dns/resolver.pyi
@@ -33,7 +33,7 @@ def zone_for_name(name, rdclass : int = rdataclass.IN, tcp=False, resolver : Opt
     ...
 
 class Resolver:
-    def __init__(self, configure):
+    def __init__(self, filename : Optional[str] = '/etc/resolv.conf', configure : Optional[bool] = True):
         self.nameservers : List[str]
     def query(self, qname : str, rdtype : Union[int,str] = rdatatype.A, rdclass : Union[int,str] = rdataclass.IN,
               tcp : bool = False, source : Optional[str] = None, raise_on_no_answer=True, source_port : int = 0):