[libvirt] [PATCH 2/3] virsh: qemu-monitor-command: Don't print extra newline with --pretty

[Ján Tomko]

On Mon, Aug 01, 2016 at 06:30:07AM +0200, Peter Krempa wrote:
>The prettified JSON string already contains a newline so don't print
>another one. This allows to pipe the json output (in conjunction with
>the --quiet option) to files without having to truncate them afterwards.
>---
> tools/virsh-domain.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
>diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
>index 6c1bc2f..45fce76 100644
>--- a/tools/virsh-domain.c
>+++ b/tools/virsh-domain.c
>@@ -8944,6 +8944,7 @@ cmdQemuMonitorCommand(vshControl *ctl, const vshCmd *cmd)
>     virBuffer buf = VIR_BUFFER_INITIALIZER;
>     bool pad = false;
>     virJSONValuePtr pretty = NULL;
>+    char *prettystr = NULL;
>
>     VSH_EXCLUSIVE_OPTIONS("hmp", "pretty");
>
>@@ -8969,22 +8970,20 @@ cmdQemuMonitorCommand(vshControl *ctl, const vshCmd *cmd)
>     if (virDomainQemuMonitorCommand(dom, monitor_cmd, &result, flags) < 0)
>         goto cleanup;
>
>-    if (vshCommandOptBool(cmd, "pretty")) {
>-        char *tmp;
>-        pretty = virJSONValueFromString(result);
>-        if (pretty && (tmp = virJSONValueToString(pretty, true))) {
>-            VIR_FREE(result);
>-            result = tmp;
>-        } else {
>-            vshResetLibvirtError();
>-        }
>+    if (vshCommandOptBool(cmd, "pretty") &&
>+        (pretty = virJSONValueFromString(result)) &&

I find naming the variable pretty pretty confusing. virJSONValuePtr is
in machine-friendly format and while it has the potential to be
formatted as pretty, it is not pretty right now.

>+        (prettystr = virJSONValueToString(pretty, true))) {
>+        vshPrint(ctl, "%s", prettystr);
>+    } else {
>+        vshResetLibvirtError();

Resetting it even when --pretty was not specified feels strange.
Also, grouping the if (--pretty) condition with the virJSONValue error
checks makes the flow hard to read.

Do we need the fallback? AFAIK there are only two issues possible when
prettifying the string:
* the system is out of memory
  possibly impossible, erroring out or even aborting virsh are
  acceptable here
* virDomainQemuMonitorCommand did not return a JSON output
  For a domain with JSON monitor, the remote side calls virJSONValueToString,
  so this could only reasonably happen with  a domain that only has HMP.
  If we error out on the --hmp --pretty combination, we can error out
  here too and do not need to fall back to raw output.

>+        vshPrint(ctl, "%s\n", result);
>     }
>-    vshPrint(ctl, "%s\n", result);
>

There is also the option of keeping the \n in vshPrint and calling
virTrimSpaces on the prettyfied output.

Jan