[sonic-cli-gen] first phase implementation of the SONiC CLI Auto-generation tool (#1644)

What I did
Implemented the sonic-cli-gen according to the SONiC CLI Auto-generation HLD

How I did it
How the sonic-cli-gen works:

Parse provided YANG model to the intermediate representation - python dictionary (you can find the structure in the sonic_cli_gen/yang_parser.py file).
Pass the python dictionary to the appropriate j2 template (config or show) and generate the CLI plugin.
Put the auto-generated CLI plugin to an appropriate location, where it can be discovered by SONiC CLI.
How to verify it
Check the file with unit tests - tests/cli_autogen_yang_parser_test.py

Command output
admin@sonic: sonic-cli-gen generate config sonic-acl
Loaded below Yang Models
['sonic-acl', 'sonic-breakout_cfg', 'sonic-crm', 'sonic-device_metadata', 'sonic-device_neighbor', 'sonic-extension', 'sonic-flex_counter', 'sonic-interface', 'sonic-loopback-interface', 'sonic-port', 'sonic-portchannel', 'sonic-types', 'sonic-versions', 'sonic-vlan', 'sonic-vrf']
Note: Below table(s) have no YANG models:
COPP_GROUP, COPP_TRAP, FEATURE, KDUMP, MGMT_INTERFACE, SNMP, SNMP_COMMUNITY, WJH, WJH_CHANNEL, 
INFO:sonic-cli-gen: Auto-generation successful! Location: /usr/local/lib/python3.7/dist-packages/config/plugins/auto/sonic-acl_yang.py
admin@sonic: sonic-cli-gen remove config sonic-acl
/usr/local/lib/python3.7/dist-packages/config/plugins/auto/sonic-acl_yang.py was removed.

Author: vadymhlushko-mlnx

clear/main.py

@@ -484,8 +484,7 @@ def remap_keys(dict):
 
 # Load plugins and register them
 helper = util_base.UtilHelper()
-for plugin in helper.load_plugins(plugins):
-    helper.register_plugin(plugin, cli)
+helper.load_and_register_plugins(plugins, cli)
 
 
 if __name__ == '__main__':

clear/plugins/auto/__init__.py

@@ -5966,8 +5966,7 @@ def smoothing_interval(interval, rates_type):
 
 # Load plugins and register them
 helper = util_base.UtilHelper()
-for plugin in helper.load_plugins(plugins):
-    helper.register_plugin(plugin, config)
+helper.load_and_register_plugins(plugins, config)
 
 
 if __name__ == '__main__':

config/main.py

@@ -23,8 +23,10 @@
         'acl_loader',
         'clear',
         'clear.plugins',
+        'clear.plugins.auto',
         'config',
         'config.plugins',
+        'config.plugins.auto',
         'connect',
         'consutil',
         'counterpoll',
@@ -48,6 +50,7 @@
         'show',
         'show.interfaces',
         'show.plugins',
+        'show.plugins.auto',
         'sonic_installer',
         'sonic_installer.bootloader',
         'sonic_package_manager',
@@ -56,6 +59,7 @@
         'undebug',
         'utilities_common',
         'watchdogutil',
+        'sonic_cli_gen',
     ],
     package_data={
         'generic_config_updater': ['generic_updater_config.conf.json'],
@@ -172,6 +176,7 @@
             'spm = sonic_package_manager.main:cli',
             'undebug = undebug.main:cli',
             'watchdogutil = watchdogutil.main:watchdogutil',
+            'sonic-cli-gen = sonic_cli_gen.main:cli',
         ]
     },
     install_requires=[

config/plugins/auto/__init__.py

@@ -1701,8 +1701,7 @@ def ztp(status, verbose):
 
 # Load plugins and register them
 helper = util_base.UtilHelper()
-for plugin in helper.load_plugins(plugins):
-    helper.register_plugin(plugin, cli)
+helper.load_and_register_plugins(plugins, cli)
 
 if __name__ == '__main__':
     cli()

setup.py

@@ -0,0 +1,8 @@
+_sonic_cli_gen_completion() {
+    COMPREPLY=( $( env COMP_WORDS="${COMP_WORDS[*]}" \
+                   COMP_CWORD=$COMP_CWORD \
+                   _SONIC_CLI_GEN_COMPLETE=complete $1 ) )
+    return 0
+}
+
+complete -F _sonic_cli_gen_completion -o default sonic-cli-gen;

show/main.py

@@ -1,2 +1,3 @@
-bash_completion.d/    /etc/
-templates/*.j2        /usr/share/sonic/templates/
+bash_completion.d/                  /etc/
+templates/*.j2                      /usr/share/sonic/templates/
+templates/sonic-cli-gen/*.j2        /usr/share/sonic/templates/sonic-cli-gen/

show/plugins/auto/__init__.py

@@ -0,0 +1,3 @@
+{% macro cli_name(name) -%}
+{{ name|lower|replace("_", "-") }}
+{%- endmacro %}