[cfggen] Add support in -v for jinja2 expression (#345)

* Add support in -v for jinja2 expression
* Format json output

Author: taoyl-ms

dockers/docker-teamd/config.sh

@@ -2,7 +2,7 @@
 
 mkdir -p /etc/teamd
 
-for pc in `sonic-cfggen -m /etc/sonic/minigraph.xml --var-keys minigraph_portchannel_interfaces`; do
+for pc in `sonic-cfggen -m /etc/sonic/minigraph.xml -v "minigraph_portchannel_interfaces.keys()"`; do
   sonic-cfggen -m /etc/sonic/minigraph.xml -a '{"pc":"'$pc'"}' -t /usr/share/sonic/templates/teamd.j2 >/etc/teamd/$pc.conf
 done
 

src/sonic-config-engine/sonic-cfggen

@@ -8,6 +8,7 @@ import jinja2
 import netaddr
 import json
 from minigraph import parse_xml
+from minigraph import minigraph_encoder
 
 
 def is_ipv4(value):
@@ -55,9 +56,9 @@ def main():
     group = parser.add_mutually_exclusive_group()
     group.add_argument("-t", "--template", help="render the data with the template file")
     group.add_argument("-s", "--alias-mapping", help="print alias mapping json if available", action='store_true')
-    group.add_argument("-v", "--var", help="print the value of a variable")
+    group.add_argument("-v", "--var", help="print the value of a variable, support jinja2 expression")
     group.add_argument("--var-json", help="print the value of a variable, in json format")
-    group.add_argument("--var-keys", help="print all keys of a map variable")
+    group.add_argument("--var-keys", help="print all keys of a map variable - to be deprecated, use -v and keys()")
     group.add_argument("--print-data", help="print all data", action='store_true')
     args = parser.parse_args()
 
@@ -94,10 +95,11 @@ def main():
         print template.render(data)
 
     if args.var != None:
-        print data[args.var]
+        template = jinja2.Template('{{' + args.var + '}}')
+        print template.render(data)
 
     if args.var_json != None:
-        print json.dumps(data[args.var_json])
+        print json.dumps(data[args.var_json], indent=4, cls=minigraph_encoder)
 
     if args.var_keys != None:
         for key in data[args.var_keys].keys():
@@ -111,7 +113,7 @@ def main():
         print json.dumps(mapping)
 
     if args.print_data:
-        print data
+        print json.dumps(data, indent=4, cls=minigraph_encoder)
 
 if __name__ == "__main__":
     main()