python: Add option for JSON output to unixctl classes and appctl.py.

This patch introduces support for different output formats to Python
Unixctl* classes and appctl.py, similar to what the previous commit did
for ovs-appctl.
In particular, tests/appctl.py gains a global option '-f,--format'
which allows users to request JSON instead of plain-text for humans.

Reported-at: https://bugzilla.redhat.com/1824861
Signed-off-by: Jakob Meng <code@jakobmeng.de>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

python/ovs/unixctl/__init__.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import enum
 import sys
 
 import ovs.util
@@ -19,6 +20,13 @@ import ovs.util
 commands = {}
 
 
+@enum.unique
+# FIXME: Use @enum.verify(enum.NAMED_FLAGS) from Python 3.11 when available.
+class UnixctlOutputFormat(enum.IntFlag):
+    TEXT = 1 << 0
+    JSON = 1 << 1
+
+
 class _UnixctlCommand(object):
     def __init__(self, usage, min_args, max_args, callback, aux):
         self.usage = usage

python/ovs/unixctl/client.py

@@ -14,6 +14,7 @@
 
 import os
 
+import ovs.json
 import ovs.jsonrpc
 import ovs.stream
 import ovs.util
@@ -41,10 +42,10 @@ class UnixctlClient(object):
             return error, None, None
 
         if reply.error is not None:
-            return 0, str(reply.error), None
+            return 0, reply.error, None
         else:
             assert reply.result is not None
-            return 0, None, str(reply.result)
+            return 0, None, reply.result
 
     def close(self):
         self._conn.close()

python/ovs/unixctl/server.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import argparse
 import copy
 import errno
 import os
@@ -35,6 +36,7 @@ class UnixctlConnection(object):
         assert isinstance(rpc, ovs.jsonrpc.Connection)
         self._rpc = rpc
         self._request_id = None
+        self._fmt = ovs.unixctl.UnixctlOutputFormat.TEXT
 
     def run(self):
         self._rpc.run()
@@ -63,10 +65,29 @@ class UnixctlConnection(object):
         return error
 
     def reply(self, body):
-        self._reply_impl(True, body)
+        assert body is None or isinstance(body, str)
+
+        if body is None:
+            body = ""
+
+        if self._fmt == ovs.unixctl.UnixctlOutputFormat.JSON:
+            body = {
+                "reply-format": "plain",
+                "reply": body
+            }
+
+        return self._reply_impl_json(True, body)
+
+    def reply_json(self, body):
+        self._reply_impl_json(True, body)
 
     def reply_error(self, body):
-        self._reply_impl(False, body)
+        assert body is None or isinstance(body, str)
+
+        if body is None:
+            body = ""
+
+        return self._reply_impl_json(False, body)
 
     # Called only by unixctl classes.
     def _close(self):
@@ -78,15 +99,11 @@ class UnixctlConnection(object):
         if not self._rpc.get_backlog():
             self._rpc.recv_wait(poller)
 
-    def _reply_impl(self, success, body):
+    def _reply_impl_json(self, success, body):
         assert isinstance(success, bool)
-        assert body is None or isinstance(body, str)
 
         assert self._request_id is not None
 
-        if body is None:
-            body = ""
-
         if success:
             reply = Message.create_reply(body, self._request_id)
         else:
@@ -133,6 +150,25 @@ def _unixctl_version(conn, unused_argv, version):
     conn.reply(version)
 
 
+def _unixctl_set_options(conn, argv, unused_aux):
+    assert isinstance(conn, UnixctlConnection)
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--format", default="text",
+                        choices=[fmt.name.lower()
+                                 for fmt in ovs.unixctl.UnixctlOutputFormat],
+                        type=str.lower)
+
+    try:
+        args = parser.parse_args(args=argv)
+    except argparse.ArgumentError as e:
+        conn.reply_error(str(e))
+        return
+
+    conn._fmt = ovs.unixctl.UnixctlOutputFormat[args.format.upper()]
+    conn.reply(None)
+
+
 class UnixctlServer(object):
     def __init__(self, listener):
         assert isinstance(listener, ovs.stream.PassiveStream)
@@ -207,4 +243,7 @@ class UnixctlServer(object):
         ovs.unixctl.command_register("version", "", 0, 0, _unixctl_version,
                                      version)
 
+        ovs.unixctl.command_register("set-options", "[--format text|json]", 1,
+                                     2, _unixctl_set_options, None)
+
         return 0, UnixctlServer(listener)