Sort out the mess around writable replicas and lookupKeyRead/Write

src/db.c

@@ -1527,7 +1527,7 @@ int expireIfNeeded(redisDb *db, robj *key, int expire_on_replica) {
     /* Deleting expired keys on a replica makes the replica inconsistent with
      * the master. The reason it's allowed for write commands is to make
      * writable replicas behave consistently. It shall not be used in readonly
-     * commands. */
+     * commands. Modules are accepted so that we don't break old modules. */
     if (expire_on_replica) {
         client *c = server.in_eval ? server.lua_client : server.current_client;
         serverAssert(!c || !c->cmd || (c->cmd->flags & (CMD_WRITE|CMD_MODULE)));

tests/integration/replication-3.tcl

@@ -64,11 +64,10 @@ start_server {tags {"repl external:skip"}} {
             r set key2 5 px 10
             r -1 select 5
             wait_for_condition 50 100 {
-                [r -1 dbsize] == 2
+                [r -1 dbsize] == 2 && [r -1 exists key1 key2] == 0
             } else {
                 fail "Replication timeout."
             }
-            after 1000
             r -1 config set slave-read-only no
             assert_equal 2 [r -1 dbsize]    ; # active expire is off
             assert_equal 1 [r -1 incr key1] ; # incr expires and re-creates key1
@@ -108,11 +107,10 @@ start_server {tags {"repl external:skip"}} {
             r pexpire key 10
             r -1 select 5
             wait_for_condition 50 100 {
-                [r -1 dbsize] == 1
+                [r -1 dbsize] == 1 && [r -1 exists key] == 0
             } else {
                 fail "Replication timeout."
             }
-            after 10
             assert_equal [r -1 pfcount key] 0 ; # expired key not used
             assert_equal [r -1 dbsize] 1      ; # but it's also not deleted
             # cleanup