[PATCH] virsh: Add QMP command wrapping for 'qemu-monitor-command'

[Peter Krempa <pkrempa@xxxxxxxxxx>]

Issuing simple QMP commands is pain as they need to be wrapped by the
JSON wrapper:

 { "execute": "COMMAND" }

and optionally also:

 { "execute": "COMMAND", "arguments":...}

For simple commands without arguments we can add syntax sugar to virsh
which allows simple usage of QMP and additionally prepares also for
passing through of the 'arguments' section:

 virsh qemu-monitor-command --qmpwrap $VM query-status

is equivalent to

 virsh qemu-monitor-command $VM '{"execute":"query-status"}'

and

 virsh qemu-monitor-command --qmpwrap $VM query-named-block-nodes '{"flat":true}'

is equivalent to

 virsh qemu-monitor-command $VM '{"execute":"query-named-block-nodes", "arguments":{"flat":true}}'

Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---

I originally called the flag '--qmp' but that could be confusing given
that we have '--hmp'. On the other hand it's shorter so I wouldn't mind
turning it back to '--qmp'.

 docs/manpages/virsh.rst |  9 ++++++++-
 tools/virsh-domain.c    | 31 ++++++++++++++++++++++++++++---
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
index 9561b3f59d..b8cb3cfbc2 100644
--- a/docs/manpages/virsh.rst
+++ b/docs/manpages/virsh.rst
@@ -7694,7 +7694,8 @@ qemu-monitor-command

 ::

-   qemu-monitor-command domain { [--hmp] | [--pretty] [--return-value] } command...
+   qemu-monitor-command domain { [--hmp] | [--qmpwrap] [--pretty]
+       [--return-value] } command...

 Send an arbitrary monitor command *command* to domain *domain* through the
 QEMU monitor.  The results of the command will be printed on stdout.
@@ -7705,6 +7706,12 @@ a space in between before passing the single command to the monitor.
 Note that libvirt uses the QMP to talk to qemu so *command* must be valid JSON
 in QMP format to work properly.

+If *--qmpwrap* is passed the first argument passed as *command* is used as a QMP
+command name and appropriately wrapped into a JSON block. Additionally a second
+argument passed as *command* is appended as value of the 'arguments' parameter
+of the QMP command verbatim. *Note* that in the future automatic formatting
+*--qmpwrap* of the arguments might be added, so scripts should format their own JSON.
+
 If *--pretty* is given the QMP reply is pretty-printed.

 If *--return-value* is given the 'return' key of the QMP response object is
diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index e5bd1fdd75..ac57196b20 100644
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -9380,6 +9380,10 @@ static const vshCmdOptDef opts_qemu_monitor_command[] = {
      .type = VSH_OT_BOOL,
      .help = N_("extract the value of the 'return' key from the returned string")
     },
+    {.name = "qmpwrap",
+     .type = VSH_OT_BOOL,
+     .help = N_("wrap the 'cmd' argument in JSON wrapper for QMP")
+    },
     {.name = "cmd",
      .type = VSH_OT_ARGV,
      .flags = VSH_OFLAG_REQ,
@@ -9405,14 +9409,35 @@ cmdQemuMonitorCommand(vshControl *ctl, const vshCmd *cmd)

     VSH_EXCLUSIVE_OPTIONS("hmp", "pretty");
     VSH_EXCLUSIVE_OPTIONS("hmp", "return-value");
+    VSH_EXCLUSIVE_OPTIONS("hmp", "qmpwrap");

     if (!(dom = virshCommandOptDomain(ctl, cmd, NULL)))
         return false;

-    while ((opt = vshCommandOptArgv(ctl, cmd, opt)))
-        virBufferAsprintf(&buf, "%s ", opt->data);
+    if (vshCommandOptBool(cmd, "qmpwrap")) {
+        const char *command = NULL;
+        const char *arguments = NULL;

-    virBufferTrim(&buf, " ");
+        if ((opt = vshCommandOptArgv(ctl, cmd, opt)))
+            command = opt->data;
+        if ((opt = vshCommandOptArgv(ctl, cmd, opt)))
+            arguments = opt->data;
+
+        if (!command || (arguments && vshCommandOptArgv(ctl, cmd, opt))) {
+            vshError(ctl, "%s", _("--qmpwrap option requires 1 or 2 arguments"));
+            return false;
+        }
+
+        virBufferAsprintf(&buf, "{\"execute\":\"%s\"", command);
+        if (arguments)
+            virBufferAsprintf(&buf, ", \"arguments\":%s", arguments);
+        virBufferAddLit(&buf, "}");
+    } else {
+        while ((opt = vshCommandOptArgv(ctl, cmd, opt)))
+            virBufferAsprintf(&buf, "%s ", opt->data);
+
+        virBufferTrim(&buf, " ");
+    }

     monitor_cmd = virBufferContentAndReset(&buf);

-- 
2.31.1