Add support for KEEPTTL option of SET command

aredis/commands/strings.py

@@ -236,14 +236,16 @@ async def psetex(self, name, time_ms, value):
             time_ms = (time_ms.seconds + time_ms.days * 24 * 3600) * 1000 + ms
         return await self.execute_command('PSETEX', name, time_ms, value)
 
-    async def set(self, name, value, ex=None, px=None, nx=False, xx=False):
+    async def set(self, name, value, ex=None, px=None, keepttl=False, nx=False, xx=False):
         """
         Set the value at key ``name`` to ``value``
 
         ``ex`` sets an expire flag on key ``name`` for ``ex`` seconds.
 
         ``px`` sets an expire flag on key ``name`` for ``px`` milliseconds.
 
+        ``keepttl`` if True, retain the time to live associated with the key.
+
         ``nx`` if set to True, set the value at key ``name`` to ``value`` if it
             does not already exist.
 
@@ -262,6 +264,8 @@ async def set(self, name, value, ex=None, px=None, nx=False, xx=False):
                 ms = int(px.microseconds / 1000)
                 px = (px.seconds + px.days * 24 * 3600) * 1000 + ms
             pieces.append(px)
+        if keepttl:
+            pieces.append('KEEPTTL')
 
         if nx:
             pieces.append('NX')

tests/client/test_commands.py

@@ -711,6 +711,17 @@ async def test_set_multipleoptions(self, r):
         assert await r.set('a', '1', xx=True, px=10000)
         assert 0 < await r.ttl('a') <= 10
 
+    @skip_if_server_version_lt('5.9.0')
+    @pytest.mark.asyncio(forbid_global_loop=True)
+    async def test_set_keepttl(self, r):
+        await r.flushdb()
+        await r.set('a', 'val')
+        assert await r.set('a', '1', xx=True, px=10000)
+        assert 0 < await r.ttl('a') <= 10
+        await r.set('a', '2', keepttl=True)
+        assert await r.get('a') == b('2')
+        assert 0 < await r.ttl('a') <= 10
+
     @pytest.mark.asyncio(forbid_global_loop=True)
     async def test_setex(self, r):
         await r.flushdb()

tests/cluster/test_commands.py

@@ -561,6 +561,17 @@ async def test_set_multipleoptions(self, r):
         assert await r.set('a', '1', xx=True, px=10000)
         assert 0 < await r.ttl('a') <= 10
 
+    @pytest.mark.asyncio
+    @skip_if_server_version_lt('5.9.0')
+    async def test_set_keepttl(self, r):
+        await r.flushdb()
+        await r.set('a', 'val')
+        assert await r.set('a', '1', xx=True, px=10000)
+        assert 0 < await r.ttl('a') <= 10
+        await r.set('a', '2', keepttl=True)
+        assert await r.get('a') == b('2')
+        assert 0 < await r.ttl('a') <= 10
+
     @pytest.mark.asyncio
     async def test_setex(self, r):
         await r.flushdb()