scripts/qmp-shell: use argparse

Use argparse instead of an open-coded CLI parser, for consistency with
everything else.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210607200649.1840382-18-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

scripts/qmp/qmp-shell

@@ -64,7 +64,7 @@
 # Use the -v and -p options to activate the verbose and pretty-print options,
 # which will echo back the properly formatted JSON-compliant QMP that is being
 # sent to QEMU, which is useful for debugging and documentation generation.
-
+import argparse
 import ast
 import atexit
 import json
@@ -401,65 +401,47 @@ def die(msg):
     sys.exit(1)
 
 
-def fail_cmdline(option=None):
-    if option:
-        sys.stderr.write('ERROR: bad command-line option \'%s\'\n' % option)
-    sys.stderr.write(
-        'qmp-shell [ -v ] [ -p ] [ -H ] [ -N ] '
-        '< UNIX socket path> | < TCP address:port >\n'
-    )
-    sys.stderr.write('    -v     Verbose (echo command sent and received)\n')
-    sys.stderr.write('    -p     Pretty-print JSON\n')
-    sys.stderr.write('    -H     Use HMP interface\n')
-    sys.stderr.write('    -N     Skip negotiate (for qemu-ga)\n')
-    sys.exit(1)
-
-
 def main():
-    addr = ''
-    qemu = None
-    hmp = False
-    pretty = False
-    verbose = False
-    negotiate = True
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-H', '--hmp', action='store_true',
+                        help='Use HMP interface')
+    parser.add_argument('-N', '--skip-negotiation', action='store_true',
+                        help='Skip negotiate (for qemu-ga)')
+    parser.add_argument('-v', '--verbose', action='store_true',
+                        help='Verbose (echo commands sent and received)')
+    parser.add_argument('-p', '--pretty', action='store_true',
+                        help='Pretty-print JSON')
 
+    default_server = os.environ.get('QMP_SOCKET')
+    parser.add_argument('qmp_server', action='store',
+                        default=default_server,
+                        help='< UNIX socket path | TCP address:port >')
+
+    args = parser.parse_args()
+    if args.qmp_server is None:
+        parser.error("QMP socket or TCP address must be specified")
+
+    qemu: QMPShell
     try:
-        for arg in sys.argv[1:]:
-            if arg == "-H":
-                if qemu is not None:
-                    fail_cmdline(arg)
-                hmp = True
-            elif arg == "-p":
-                pretty = True
-            elif arg == "-N":
-                negotiate = False
-            elif arg == "-v":
-                verbose = True
-            else:
-                if qemu is not None:
-                    fail_cmdline(arg)
-                if hmp:
-                    qemu = HMPShell(arg)
-                else:
-                    qemu = QMPShell(arg, pretty)
-                addr = arg
-
-        if qemu is None:
-            fail_cmdline()
+        if args.hmp:
+            qemu = HMPShell(args.qmp_server)
+        else:
+            qemu = QMPShell(args.qmp_server, args.pretty)
     except qmp.QMPBadPortError:
-        die('bad port number in command-line')
+        parser.error(f"Bad port number: {args.qmp_server}")
+        return  # pycharm doesn't know error() is noreturn
 
     try:
-        qemu.connect(negotiate)
+        qemu.connect(negotiate=not args.skip_negotiation)
     except qmp.QMPConnectError:
-        die('Didn\'t get QMP greeting message')
+        die("Didn't get QMP greeting message")
     except qmp.QMPCapabilitiesError:
-        die('Could not negotiate capabilities')
-    except OSError:
-        die('Could not connect to %s' % addr)
+        die("Couldn't negotiate capabilities")
+    except OSError as err:
+        die(f"Couldn't connect to {args.qmp_server}: {err!s}")
 
     qemu.show_banner()
-    qemu.set_verbosity(verbose)
+    qemu.set_verbosity(args.verbose)
     while qemu.read_exec_command(qemu.get_prompt()):
         pass
     qemu.close()