Add canonical_name() to async resolver too.

3 files changed, 51 insertions, 0 deletions

diff --git a/dns/asyncresolver.py b/dns/asyncresolver.py
index 3ac334f..0aaeb9c 100644
--- a/dns/asyncresolver.py
+++ b/dns/asyncresolver.py
@@ -165,6 +165,28 @@ class Resolver(dns.resolver.Resolver):
                                   rdclass=dns.rdataclass.IN,
                                   *args, **kwargs)
 
+    async def canonical_name(self, name):
+        """Determine the canonical name of *name*.
+
+        The canonical name is the name the resolver uses for queries
+        after all CNAME and DNAME renamings have been applied.
+
+        *name*, a ``dns.name.Name`` or ``str``, the query name.
+
+        This method can raise any exception that ``resolve()`` can
+        raise, other than ``dns.resolver.NoAnswer`` and
+        ``dns.resolver.NXDOMAIN``.
+
+        Returns a ``dns.name.Name``.
+        """
+        try:
+            answer = await self.resolve(name, raise_on_no_answer=False)
+            canonical_name = answer.canonical_name
+        except dns.resolver.NXDOMAIN as e:
+            canonical_name = e.canonical_name
+        return canonical_name
+
+
 default_resolver = None
 
 
@@ -212,6 +234,14 @@ async def resolve_address(ipaddr, *args, **kwargs):
 
     return await get_default_resolver().resolve_address(ipaddr, *args, **kwargs)
 
+async def canonical_name(name):
+    """Determine the canonical name of *name*.
+
+    See ``dns.resolver.Resolver.canonical_name`` for more information on the
+    parameters and possible exceptions.
+    """
+
+    return await get_default_resolver().canonical_name(name)
 
 async def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False,
                         resolver=None, backend=None):
diff --git a/doc/async-resolver-functions.rst b/doc/async-resolver-functions.rst
index fc5798a..b2669f3 100644
--- a/doc/async-resolver-functions.rst
+++ b/doc/async-resolver-functions.rst
@@ -5,4 +5,5 @@ Asynchronous Resolver Functions
 
 .. autofunction:: dns.asyncresolver.resolve
 .. autofunction:: dns.asyncresolver.resolve_address
+.. autofunction:: dns.asyncresolver.canonical_name
 .. autofunction:: dns.asyncresolver.zone_for_name
diff --git a/tests/test_async.py b/tests/test_async.py
index db108c8..690a1eb 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -182,6 +182,26 @@ class AsyncTests(unittest.TestCase):
         dnsgoogle = dns.name.from_text('dns.google.')
         self.assertEqual(answer[0].target, dnsgoogle)
 
+    def testCanonicalNameNoCNAME(self):
+        cname = dns.name.from_text('www.google.com')
+        async def run():
+            return await dns.asyncresolver.canonical_name('www.google.com')
+        self.assertEqual(self.async_run(run), cname)
+
+    def testCanonicalNameCNAME(self):
+        name = dns.name.from_text('www.dnspython.org')
+        cname = dns.name.from_text('dmfrjf4ips8xa.cloudfront.net')
+        async def run():
+            return await dns.asyncresolver.canonical_name(name)
+        self.assertEqual(self.async_run(run), cname)
+
+    def testCanonicalNameDangling(self):
+        name = dns.name.from_text('dangling-cname.dnspython.org')
+        cname = dns.name.from_text('dangling-target.dnspython.org')
+        async def run():
+            return await dns.asyncresolver.canonical_name(name)
+        self.assertEqual(self.async_run(run), cname)
+
     def testResolverBadScheme(self):
         res = dns.asyncresolver.Resolver(configure=False)
         res.nameservers = ['bogus://dns.google/dns-query']