PERSIST: a fix and some basic test

src/db.c

@@ -532,9 +532,11 @@ void persistCommand(redisClient *c) {
     if (de == NULL) {
         addReply(c,shared.czero);
     } else {
-        if (removeExpire(c->db,c->argv[1]))
+        if (removeExpire(c->db,c->argv[1])) {
             addReply(c,shared.cone);
-        else
+            server.dirty++;
+        } else {
             addReply(c,shared.czero);
         }
+    }
 }

tests/unit/expire.tcl

@@ -60,4 +60,15 @@ start_server {tags {"expire"}} {
         catch {r setex z -10 foo} e
         set _ $e
     } {*invalid expire*}
+
+    test {PERSIST can undo an EXPIRE} {
+        r set x foo
+        r expire x 50
+        list [r ttl x] [r persist x] [r ttl x] [r get x]
+    } {50 1 -1 foo}
+
+    test {PERSIST returns 0 against non existing or non volatile keys} {
+        r set x foo
+        list [r persist foo] [r persist nokeyatall]
+    } {0 0}
 }