Supports bash_completion for ceilometerclient

bash_completion feature can improve CLI user experience, projects like
nova, keystone, and cinder already support it.

NOTE: this patch just provides simple functionality, which means cache
for IDs and names is not used (like nova).

Change-Id: I1b04998a5e7c8818aed4b51f5fe5bf01efd0e14a
Closes-Bug: #1260939

ceilometerclient/shell.py

@@ -186,9 +186,19 @@ class CeilometerShell(object):
         submodule = utils.import_versioned_module(version, 'shell')
         self._find_actions(subparsers, submodule)
         self._find_actions(subparsers, self)
+        self._add_bash_completion_subparser(subparsers)
 
         return parser
 
+    def _add_bash_completion_subparser(self, subparsers):
+        subparser = subparsers.add_parser(
+            'bash_completion',
+            add_help=False,
+            formatter_class=HelpFormatter
+        )
+        self.subcommands['bash_completion'] = subparser
+        subparser.set_defaults(func=self.do_bash_completion)
+
     def _find_actions(self, subparsers, actions_module):
         for attr in (a for a in dir(actions_module) if a.startswith('do_')):
             # I prefer to be hypen-separated instead of underscores.
@@ -241,6 +251,9 @@ class CeilometerShell(object):
         if args.func == self.do_help:
             self.do_help(args)
             return 0
+        elif args.func == self.do_bash_completion:
+            self.do_bash_completion(args)
+            return 0
 
         if not (args.os_auth_token and args.ceilometer_url):
             if not args.os_username:
@@ -270,6 +283,22 @@ class CeilometerShell(object):
         except exc.Unauthorized:
             raise exc.CommandError("Invalid OpenStack Identity credentials.")
 
+    def do_bash_completion(self, args):
+        """Prints all of the commands and options to stdout.
+
+        The ceilometer.bash_completion script doesn't have to hard code them.
+        """
+        commands = set()
+        options = set()
+        for sc_str, sc in self.subcommands.items():
+            commands.add(sc_str)
+            for option in list(sc._optionals._option_string_actions):
+                options.add(option)
+
+        commands.remove('bash-completion')
+        commands.remove('bash_completion')
+        print(' '.join(commands | options))
+
     @utils.arg('command', metavar='<subcommand>', nargs='?',
                help='Display help for <subcommand>')
     def do_help(self, args):

tools/ceilometer.bash_completion

@@ -0,0 +1,27 @@
+# bash completion for openstack ceilometer
+
+_ceilometer_opts="" # lazy init
+_ceilometer_flags="" # lazy init
+_ceilometer_opts_exp="" # lazy init
+_ceilometer()
+{
+    local cur prev kbc
+    COMPREPLY=()
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    prev="${COMP_WORDS[COMP_CWORD-1]}"
+
+    if [ "x$_ceilometer_opts" == "x" ] ; then
+        kbc="`ceilometer bash-completion | sed -e "s/ -h / /"`"
+        _ceilometer_opts="`echo "$kbc" | sed -e "s/--[a-z0-9_-]*//g" -e "s/[ ][ ]*/ /g"`"
+        _ceilometer_flags="`echo " $kbc" | sed -e "s/ [^-][^-][a-z0-9_-]*//g" -e "s/[ ][ ]*/ /g"`"
+        _ceilometer_opts_exp="`echo $_ceilometer_opts | sed -e "s/[ ]/|/g"`"
+    fi
+
+    if [[ " ${COMP_WORDS[@]} " =~ " "($_ceilometer_opts_exp)" " && "$prev" != "help" ]] ; then
+        COMPREPLY=($(compgen -W "${_ceilometer_flags}" -- ${cur}))
+    else
+        COMPREPLY=($(compgen -W "${_ceilometer_opts}" -- ${cur}))
+    fi
+    return 0
+}
+complete -F _ceilometer ceilometer