scripts/qmp-shell: Fix empty-transaction invocation

calling "transaction( )" is pointless, but valid. Rework the parser to
allow this kind of invocation. This helps clean up exception handling
later by removing accidental breakages of the parser that aren't
explicitly forbidden.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210607200649.1840382-35-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

diff --git a/scripts/qmp/qmp-shell b/scripts/qmp/qmp-shell
index 3c32b576a37d5f588f18283494dcd050b5c33427..78e4eae00754b0f9c551c52696b7d5e7ee435627 100755 (executable)
--- a/scripts/qmp/qmp-shell
+++ b/scripts/qmp/qmp-shell
@@ -244,11 +244,14 @@ class QMPShell(qmp.QEMUMonitorProtocol):
         cmdargs = re.findall(argument_regex, cmdline)
         qmpcmd: QMPMessage
 
-        # Transactional CLI entry/exit:
-        if cmdargs[0] == 'transaction(':
+        # Transactional CLI entry:
+        if cmdargs and cmdargs[0] == 'transaction(':
             self._transmode = True
+            self._actions = []
             cmdargs.pop(0)
-        elif cmdargs[0] == ')' and self._transmode:
+
+        # Transactional CLI exit:
+        if cmdargs and cmdargs[0] == ')' and self._transmode:
             self._transmode = False
             if len(cmdargs) > 1:
                 msg = 'Unexpected input after close of Transaction sub-shell'
@@ -257,15 +260,14 @@ class QMPShell(qmp.QEMUMonitorProtocol):
                 'execute': 'transaction',
                 'arguments': {'actions': self._actions}
             }
-            self._actions = list()
             return qmpcmd
 
-        # Nothing to process?
+        # No args, or no args remaining
         if not cmdargs:
             return None
 
-        # Parse and then cache this Transactional Action
         if self._transmode:
+            # Parse and cache this Transactional Action
             finalize = False
             action = {'type': cmdargs[0], 'data': {}}
             if cmdargs[-1] == ')':