From: Peter Krempa <pkrempa@redhat.com>

As no argument parsing is employed the script is hard to use and when
running without arguments it blurbs:

 $ ./scripts/render_block_graph.py
 Traceback (most recent call last):
   File "/home/pipo/git/qemu.git/./scripts/render_block_graph.py", line 135, in <module>
     obj = sys.argv[1]
          ~~~~~~~~^^^
 IndexError: list index out of range

instead of an actionable error. The user then usually needs to read the
script to understand arguments.

Implement proper argument parsing via 'argparse'. The following
arguments will be supported:

  $ ./scripts/render_block_graph.py --help
  usage: render_block_graph.py [-h] (--socket SOCKET | --vm VM) [--uri URI] [--output OUTPUT]

  Tool that renders the qemu block graph into a image.

  options:
    -h, --help       show this help message and exit
    --socket SOCKET  socket mode - path to qemu monitor socket
    --vm VM          libvirt mode - name of libvirt VM
    --uri URI        libvirt URI to connect to
    --output OUTPUT  path to output image (.png suffix added); in libvirt mode default is the name of the VM

Usage then requires one of '--vm' or '--socket'. In libvirt mode the
output file is by default populated from the VM name and the '--uri'
parameter allows overriding the libvirt connection uri.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 scripts/render_block_graph.py | 51 ++++++++++++++++++++++++++++-------
 1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/scripts/render_block_graph.py b/scripts/render_block_graph.py
index 14b2d02ec2..6f668dec51 100755
--- a/scripts/render_block_graph.py
+++ b/scripts/render_block_graph.py
@@ -23,6 +23,7 @@
 import subprocess
 import json
 from graphviz import Digraph
+import argparse

 sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'python'))
 from qemu.qmp import QMPError
@@ -91,13 +92,19 @@ def render_block_graph(qmp, filename, format='png'):


 class LibvirtGuest():
-    def __init__(self, name):
+    def __init__(self, name, uri=None):
         self.name = name
+        self.uri = uri

     def cmd(self, cmd):
         # only supports qmp commands without parameters
         m = {'execute': cmd}
-        ar = ['virsh', 'qemu-monitor-command', self.name, json.dumps(m)]
+        ar = ['virsh']
+
+        if self.uri:
+            ar += ['-c', self.uri]
+
+        ar += ['qemu-monitor-command', self.name, json.dumps(m)]

         reply = json.loads(subprocess.check_output(ar))

@@ -108,15 +115,39 @@ def cmd(self, cmd):


 if __name__ == '__main__':
-    obj = sys.argv[1]
-    out = sys.argv[2]
+    parser = argparse.ArgumentParser(
+            description='Tool that renders the qemu block graph into a image.')
+
+    modegroup = parser.add_mutually_exclusive_group(required=True)
+
+    modegroup.add_argument('--socket',
+                           help='socket mode - path to qemu monitor socket')
+    modegroup.add_argument('--vm', help='libvirt mode - name of libvirt VM')
+
+    parser.add_argument('--uri', help='libvirt URI to connect to')
+
+    parser.add_argument('--output',
+                        help='path to output image (.png suffix added); '
+                             'in libvirt mode default is the name of the VM')

-    if os.path.exists(obj):
-        # assume unix socket
-        qmp = QEMUMonitorProtocol(obj)
+    args = parser.parse_args()
+
+    if args.socket:
+        if not args.output:
+            print("--output required in socket mode", file=sys.stderr)
+            parser.print_usage()
+            sys.exit(1)
+
+        qmp = QEMUMonitorProtocol(args.socket)
         qmp.connect()
-    else:
-        # assume libvirt guest name
-        qmp = LibvirtGuest(obj)
+        out = args.output
+
+    if args.vm:
+        qmp = LibvirtGuest(args.vm, args.uri)
+
+        if args.output:
+            out = args.output
+        else:
+            out = args.vm

     render_block_graph(qmp, out)
-- 
2.48.1