[PULL 64/72] scripts/qmp-shell: Fix empty-transaction invocation

[John Snow]

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>
---
 scripts/qmp/qmp-shell | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/scripts/qmp/qmp-shell b/scripts/qmp/qmp-shell
index 3c32b576a3..78e4eae007 100755
--- 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] == ')':
-- 
2.31.1