Add support for a general network-get helper

MANIFEST.in

@@ -3,4 +3,5 @@ include Makefile
 include VERSION
 include MANIFEST.in
 include scripts/*
+include README.md
 recursive-include debian *

charmhelpers/core/hookenv.py

@@ -1093,6 +1093,24 @@ def network_get_primary_address(binding):
     return subprocess.check_output(cmd).decode('UTF-8').strip()
 
 
+@translate_exc(from_exc=OSError, to_exc=NotImplementedError)
+def network_get(endpoint, relation_id=None):
+    """
+    Retrieve the network details for a relation endpoint
+
+    :param endpoint: string. The name of a relation endpoint
+    :param relation_id: int. The ID of the relation for the current context.
+    :return: dict. The loaded YAML output of the network-get query.
+    :raise: NotImplementedError if run on Juju < 2.0
+    """
+    cmd = ['network-get', endpoint, '--format', 'yaml']
+    if relation_id:
+        cmd.append('-r')
+        cmd.append(relation_id)
+    response = subprocess.check_output(cmd).decode('UTF-8').strip()
+    return yaml.safe_load(response)
+
+
 def add_metric(*args, **kwargs):
     """Add metric values. Values may be expressed with keyword arguments. For
     metric names containing dashes, these may be expressed as one or more

tests/core/test_hookenv.py

@@ -1661,7 +1661,7 @@ def test_storage_get_with_id(self, check_output):
 
     @patch('subprocess.check_output')
     def test_network_get_primary(self, check_output):
-        '''Ensure that network-get is called correctly and output is returned'''
+        """Ensure that network-get is called correctly and output is returned"""
         check_output.return_value = b'192.168.22.1'
         ip = hookenv.network_get_primary_address('mybinding')
         check_output.assert_called_with(
@@ -1670,11 +1670,44 @@ def test_network_get_primary(self, check_output):
 
     @patch('subprocess.check_output')
     def test_network_get_primary_unsupported(self, check_output):
-        '''Ensure that NotImplementedError is thrown when run on Juju < 2.0'''
+        """Ensure that NotImplementedError is thrown when run on Juju < 2.0"""
         check_output.side_effect = OSError(2, 'network-get')
         self.assertRaises(NotImplementedError, hookenv.network_get_primary_address,
                           'mybinding')
 
+    @patch('subprocess.check_output')
+    def test_network_get(self, check_output):
+        """Ensure that network-get is called correctly"""
+        check_output.return_value = b'192l.l168.22.1'
+        hookenv.network_get('mybinding')
+        check_output.assert_called_with(
+            ['network-get', 'mybinding', '--format', 'yaml'])
+
+    @patch('subprocess.check_output')
+    def test_network_get_relation_bound(self, check_output):
+        """Ensure that network-get supports relation context"""
+        check_output.return_value = b'192l.l168.22.1'
+        hookenv.network_get('mybinding', 'db')
+        check_output.assert_called_with(
+            ['network-get', 'mybinding', '--format', 'yaml', '-r', 'db'])
+
+    @patch('subprocess.check_output')
+    def test_network_get_parses_yaml(self, check_output):
+        """network-get returns loaded YAML output."""
+        check_output.return_value = b"""
+bind-addresses:
+- macaddress: ""
+  interfacename: ""
+  addresses:
+    - address: 10.136.107.33
+      cidr: ""
+ingress-addresses:
+- 10.136.107.33
+        """
+        ip = hookenv.network_get('mybinding')
+        self.assertEqual(len(ip['bind-addresses']), 1)
+        self.assertEqual(ip['ingress-addresses'], ['10.136.107.33'])
+
     @patch('subprocess.check_call')
     def test_add_metric(self, check_call_):
         hookenv.add_metric(flips='1.5', flops='2.1')