Handle key has only metadata and no value

Some other etcd clients may add key
 without providing 'value'.

This patch adds compatibility, so etcd can be used
together with another clients

Closes-bug: #1967674
Change-Id: I6319d58462481aac4b15048aad57de77094e8769

etcd3gw/client.py

@@ -231,12 +231,11 @@ class Etcd3Client(object):
         if metadata:
             def value_with_metadata(item):
                 item['key'] = _decode(item['key'])
-                value = _decode(item.pop('value'))
+                value = _decode(item.pop('value', ''))
                 return value, item
-
             return [value_with_metadata(item) for item in result['kvs']]
-        else:
-            return [_decode(item['value']) for item in result['kvs']]
+
+        return [_decode(item.get('value', '')) for item in result['kvs']]
 
     def get_all(self, sort_order=None, sort_target='key'):
         """Get all keys currently stored in etcd.

etcd3gw/tests/test_etcd3gw.py

@@ -31,6 +31,7 @@ import urllib3
 from etcd3gw.client import Etcd3Client
 from etcd3gw import exceptions
 from etcd3gw.tests import base
+from etcd3gw import utils
 
 try:
     # Python 3.8 : time.clock was deprecated and removed.
@@ -448,3 +449,44 @@ class TestEtcd3Gateway(base.TestCase):
             self.fail("watch timed out when server responded with unicode")
 
         self.assertEqual(res, {'kv': {'key': b'value'}})
+
+    def _post_key(self, key_name, provide_value=True):
+        payload = {"key": utils._encode(key_name)}
+        if provide_value:
+            payload["value"] = utils._encode(key_name)
+        self.client.post(self.client.get_url("/kv/put"), json=payload)
+
+    @unittest.skipUnless(
+        _is_etcd3_running(), "etcd3 is not available")
+    def test_client_keys_with_metadata_and_value(self):
+        test_key_value = b"some_key"
+        self._post_key(test_key_value)
+        result = self.client.get(test_key_value, metadata=True)
+        self.assertTrue(
+            len(result) > 0,
+            str(test_key_value) + " key is not found in etcd"
+        )
+        value, metadata = result[0]
+        self.assertEqual(
+            value,
+            test_key_value,
+            "unable to get value for " + str(test_key_value)
+        )
+
+    @unittest.skipUnless(
+        _is_etcd3_running(), "etcd3 is not available")
+    def test_client_keys_with_metadata_and_no_value(self):
+        value_is_not_set_default = b""
+        test_key = b"some_key"
+        self._post_key(test_key, provide_value=False)
+        result = self.client.get(test_key, metadata=True)
+        self.assertTrue(
+            len(result) > 0,
+            str(test_key) + " key is not found in etcd"
+        )
+        value, metadata = result[0]
+        self.assertEqual(
+            value,
+            value_is_not_set_default,
+            "unable to get value for " + str(test_key)
+        )

releasenotes/notes/bug-1967674-102b70275b1627cd.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Add compatibility with another etcd clients, that may have not provide value while posting a key