Implement <cancel-commit> operation (#22)

<cancel-commit> is a part of Confirmed Commit Capability, however
it wasn't implemented before.

netconf_client/ncclient.py

@@ -4,6 +4,7 @@
 import inspect
 from concurrent.futures import CancelledError, TimeoutError
 from queue import Empty
+from typing import Optional
 import time
 
 from lxml import etree
@@ -16,6 +17,7 @@
     copy_config,
     discard_changes,
     commit,
+    cancel_commit,
     lock,
     unlock,
     kill_session,
@@ -372,6 +374,15 @@ def commit(
         )
         self._send_rpc(rpc_xml)
 
+    def cancel_commit(self, persist_id: Optional[str] = None):
+        """Send a ``<cancel-commit>`` request
+
+        :param str persist_id: A persistent confirmed commit id given in the ``<commit>``
+                               request. Can be None (default), if ``<cancel-commit>`` is issued
+                               on the same session that issued the confirmed commit.
+        """
+        self._send_rpc(cancel_commit(persist_id))
+
     def lock(self, target):
         """Send a ``<lock>`` request
 

netconf_client/rpc.py

@@ -1,4 +1,6 @@
 import uuid
+from typing import Optional
+
 from lxml import etree
 
 
@@ -96,6 +98,17 @@ def commit(
     return make_rpc("".join(pieces), msg_id=msg_id)
 
 
+def cancel_commit(persist_id: Optional[str] = None, msg_id=None):
+    pieces = []
+    pieces.append("<cancel-commit>")
+
+    if persist_id:
+        pieces.append(f"<persist-id>{persist_id}</persist-id>")
+
+    pieces.append("</cancel-commit>")
+    return make_rpc("".join(pieces), msg_id=msg_id)
+
+
 def lock(target, msg_id=None):
     pieces = []
     pieces.append("<lock>")

test/test_manager.py

@@ -416,6 +416,49 @@ def test_commit(session, fake_id):
         )
 
 
+def test_cancel_commit_default_0(session, fake_id):
+    session.replies.append(None)
+    with Manager(session, timeout=1) as mgr:
+        mgr.cancel_commit()
+        assert session.sent[0] == uglify(
+            """
+            <rpc message-id="fake-id" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
+              <cancel-commit>
+              </cancel-commit>
+            </rpc>
+            """
+        )
+
+
+def test_cancel_commit_default_1(session, fake_id):
+    session.replies.append(None)
+    with Manager(session, timeout=1) as mgr:
+        mgr.cancel_commit(persist_id="")
+        assert session.sent[0] == uglify(
+            """
+            <rpc message-id="fake-id" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
+              <cancel-commit>
+              </cancel-commit>
+            </rpc>
+            """
+        )
+
+
+def test_cancel_commit_persist_id(session, fake_id):
+    session.replies.append(None)
+    with Manager(session, timeout=1) as mgr:
+        mgr.cancel_commit(persist_id="IQ,d4668")
+        assert session.sent[0] == uglify(
+            """
+            <rpc message-id="fake-id" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
+              <cancel-commit>
+                <persist-id>IQ,d4668</persist-id>
+              </cancel-commit>
+            </rpc>
+            """
+        )
+
+
 def test_lock(session, fake_id):
     session.replies.append(None)
     with Manager(session, timeout=1) as mgr: