[Qemu-block] [PATCH v6 10/11] iotests: implement pretty-print for log and qmp_log

[John Snow]

If iotests have lines exceeding >998 characters long, git doesn't
want to send it plaintext to the list. We can solve this by allowing
the iotests to use pretty printed QMP output that we can match against
instead.

As a bonus, it's much nicer for human eyes too.

Signed-off-by: John Snow <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 tests/qemu-iotests/iotests.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index a96a7010d4..cbedfaf1df 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -288,13 +288,18 @@ def filter_img_info(output, filename):
         lines.append(line)
     return '\n'.join(lines)
 
-def log(msg, filters=[]):
+def log(msg, filters=[], indent=None):
+    '''Logs either a string message or a JSON serializable message (like QMP).
+    If indent is provided, JSON serializable messages are pretty-printed.'''
     for flt in filters:
         msg = flt(msg)
     if isinstance(msg, dict) or isinstance(msg, list):
+        # Python < 3.4 needs to know not to add whitespace when 
pretty-printing:
+        separators = (', ', ': ') if indent is None else (',', ': ')
         # Don't sort if it's already sorted
         do_sort = not isinstance(msg, OrderedDict)
-        print(json.dumps(msg, sort_keys=do_sort))
+        print(json.dumps(msg, sort_keys=do_sort,
+                         indent=indent, separators=separators))
     else:
         print(msg)
 
@@ -483,14 +488,14 @@ class VM(qtest.QEMUQtestMachine):
             result.append(filter_qmp_event(ev))
         return result
 
-    def qmp_log(self, cmd, filters=[], **kwargs):
+    def qmp_log(self, cmd, filters=[], indent=None, **kwargs):
         full_cmd = OrderedDict((
             ("execute", cmd),
             ("arguments", ordered_kwargs(kwargs))
         ))
-        log(full_cmd, filters)
+        log(full_cmd, filters, indent=indent)
         result = self.qmp(cmd, **kwargs)
-        log(result, filters)
+        log(result, filters, indent=indent)
         return result
 
     def run_job(self, job, auto_finalize=True, auto_dismiss=False):
-- 
2.17.2