Implement HRANDFIELD

Fix #156

docs/redis-commands/Redis.md

@@ -1276,6 +1276,10 @@ Returns the values of all fields in a hash.
 
 Sets the values of multiple fields.
 
+### [HRANDFIELD](https://redis.io/commands/hrandfield/)
+
+Returns one or more random fields from a hash.
+
 ### [HSCAN](https://redis.io/commands/hscan/)
 
 Iterates over fields and values of a hash.
@@ -1297,13 +1301,6 @@ Returns the length of the value of a field.
 Returns all values in a hash.
 
 
-### Unsupported hash commands 
-> To implement support for a command, see [here](/guides/implement-command/) 
-
-#### [HRANDFIELD](https://redis.io/commands/hrandfield/) <small>(not implemented)</small>
-
-Returns one or more random fields from a hash.
-
 
 ## hyperloglog commands
 

fakeredis/commands_mixins/hash_mixin.py

@@ -1,9 +1,10 @@
 import itertools
 import math
+import random
 
 from fakeredis import _msgs as msgs
 from fakeredis._commands import (command, Key, Hash, Int, Float)
-from fakeredis._helpers import (SimpleError, OK)
+from fakeredis._helpers import (SimpleError, OK, casematch)
 
 
 class HashCommandsMixin:
@@ -98,3 +99,25 @@ def hstrlen(self, key, field):
     @command((Key(Hash),))
     def hvals(self, key):
         return list(key.value.values())
+
+    @command(name='HRANDFIELD', fixed=(Key(Hash),), repeat=(bytes,))
+    def hrandfield(self, key, *args):
+        if len(args) > 2:
+            raise SimpleError(msgs.SYNTAX_ERROR_MSG)
+        if key.value is None or len(key.value) == 0:
+            return None
+        count = min(Int.decode(args[0]) if len(args) >= 1 else 1, len(key.value))
+        withvalues = casematch(args[1], b"withvalues") if len(args) >= 2 else False
+        if count == 0:
+            return list()
+
+        if count < 0:  # Allow repetitions
+            res = random.choices(sorted(key.value.items()), k=-count)
+        else:  # Unique values from hash
+            res = random.sample(sorted(key.value.items()), count)
+
+        if withvalues:
+            res = [item for t in res for item in t]
+        else:
+            res = [t[0] for t in res]
+        return res

test/test_mixins/test_hash_commands.py

@@ -2,6 +2,8 @@
 import redis
 import redis.client
 
+from test import testtools
+
 
 # Tests for the hash type.
 
@@ -289,3 +291,29 @@ def test_hscan(r: redis.Redis):
     assert b'key:7' in results
     assert b'key:17' in results
     assert len(results) == 2
+
+
+def test_hrandfield(r: redis.Redis):
+    assert r.hrandfield("key") is None
+    hash = {b"a": 1, b"b": 2, b"c": 3, b"d": 4, b"e": 5}
+    r.hset("key", mapping=hash)
+    assert r.hrandfield("key") is not None
+    assert len(r.hrandfield("key", 0)) == 0
+    res = r.hrandfield("key", 2)
+    assert len(res) == 2
+    assert res[0] in set(hash.keys())
+    assert res[1] in set(hash.keys())
+    # with values
+    res = r.hrandfield("key", 2, True)
+    assert len(res) == 4
+    assert res[0] in set(hash.keys())
+    assert res[1] in {str(x).encode() for x in hash.values()}
+    assert res[2] in set(hash.keys())
+    assert res[3] in {str(x).encode() for x in hash.values()}
+    # without duplications
+    assert len(r.hrandfield("key", 10)) == 5
+    # with duplications
+    assert len(r.hrandfield("key", -10)) == 10
+
+    with pytest.raises(redis.ResponseError):
+        testtools.raw_command(r, 'HRANDFIELD', 'key', 3, 'WITHVALUES', 3)