Add SIMPLE_STRING reply type to the Module API

This commit adds the `SIMPLE_STRING` reply type to the Module API, which is
required for scripts to process correctly the reply type of commands
called inside scripts.

Before this change, commands like `PING` or `SET`, which return `"OK"`
as a simple string reply, would be returned as string replies to scripts.
To allow the support of the Lua engine as an external module, we need to
distinguish between simple string and string replies to keep backward
compatibility.

Signed-off-by: Ricardo Dias <ricardo.dias@percona.com>

Author: rjd15372

src/call_reply.c

@@ -27,7 +27,9 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "script.h"
 #include "server.h"
+#include "valkeymodule.h"
 #include "call_reply.h"
 
 #define REPLY_FLAG_ROOT (1 << 0)
@@ -102,7 +104,12 @@ static void callReplyError(void *ctx, const char *str, size_t len, const char *p
 
 static void callReplySimpleStr(void *ctx, const char *str, size_t len, const char *proto, size_t proto_len) {
     CallReply *rep = ctx;
-    callReplySetSharedData(rep, VALKEYMODULE_REPLY_STRING, proto, proto_len, 0);
+    int type = VALKEYMODULE_REPLY_STRING;
+    if (scriptIsRunning()) {
+        /* In scripts, simple strings replies should not be converted to string replies. */
+        type = VALKEYMODULE_REPLY_SIMPLE_STRING;
+    }
+    callReplySetSharedData(rep, type, proto, proto_len, 0);
     rep->len = len;
     rep->val.str = str;
 }
@@ -306,6 +313,7 @@ int callReplyType(CallReply *rep) {
 
 /* Return reply string as buffer and len. Applicable to:
  * - VALKEYMODULE_REPLY_STRING
+ * - VALKEYMODULE_REPLY_SIMPLE_STRING
  * - VALKEYMODULE_REPLY_ERROR
  *
  * The return value is borrowed from CallReply, so it must not be freed
@@ -316,7 +324,7 @@ int callReplyType(CallReply *rep) {
  */
 const char *callReplyGetString(CallReply *rep, size_t *len) {
     callReplyParse(rep);
-    if (rep->type != VALKEYMODULE_REPLY_STRING && rep->type != VALKEYMODULE_REPLY_ERROR) return NULL;
+    if (rep->type != VALKEYMODULE_REPLY_STRING && rep->type != VALKEYMODULE_REPLY_SIMPLE_STRING && rep->type != VALKEYMODULE_REPLY_ERROR) return NULL;
     if (len) *len = rep->len;
     return rep->val.str;
 }

src/call_reply.h

@@ -33,7 +33,6 @@
 #include "resp_parser.h"
 
 typedef struct CallReply CallReply;
-typedef void (*ValkeyModuleOnUnblocked)(void *ctx, CallReply *reply, void *private_data);
 
 CallReply *callReplyCreate(sds reply, list *deferred_error_list, void *private_data);
 CallReply *callReplyCreateError(sds reply, void *private_data);

src/module.c

@@ -267,6 +267,7 @@ typedef struct ValkeyModuleCommand ValkeyModuleCommand;
  * way depending on the function called on the reply structure. By default
  * only the type, proto and protolen are filled. */
 typedef struct CallReply ValkeyModuleCallReply;
+typedef void (*ValkeyModuleOnUnblocked)(void *ctx, ValkeyModuleCallReply *reply, void *private_data);
 
 /* Structure to hold the module auth callback & the Module implementing it. */
 typedef struct ValkeyModuleAuthCtx {
@@ -6178,6 +6179,7 @@ ValkeyModuleString *VM_CreateStringFromCallReply(ValkeyModuleCallReply *reply) {
     const char *str;
     switch (callReplyType(reply)) {
     case VALKEYMODULE_REPLY_STRING:
+    case VALKEYMODULE_REPLY_SIMPLE_STRING:
     case VALKEYMODULE_REPLY_ERROR: str = callReplyGetString(reply, &len); return VM_CreateString(ctx, str, len);
     case VALKEYMODULE_REPLY_INTEGER: {
         char buf[64];

src/script.h

@@ -30,6 +30,9 @@
 #ifndef __SCRIPT_H_
 #define __SCRIPT_H_
 
+#include "sds.h"
+#include "monotonic.h"
+
 /*
  * Script.c unit provides an API for functions and eval
  * to interact with the server. Interaction includes mostly
@@ -67,6 +70,8 @@
 #define SCRIPT_ALLOW_CROSS_SLOT (1ULL << 8) /* Indicate that the current script may access keys from multiple slots */
 typedef struct scriptRunCtx scriptRunCtx;
 
+typedef struct client client;
+
 /* This struct stores the necessary information to manage the execution of
  * scripts using EVAL and FCALL. */
 struct scriptRunCtx {

src/valkeymodule.h

@@ -112,6 +112,7 @@ typedef long long ustime_t;
 #define VALKEYMODULE_REPLY_VERBATIM_STRING 10
 #define VALKEYMODULE_REPLY_ATTRIBUTE 11
 #define VALKEYMODULE_REPLY_PROMISE 12
+#define VALKEYMODULE_REPLY_SIMPLE_STRING 13
 
 /* Postponed array length. */
 #define VALKEYMODULE_POSTPONED_ARRAY_LEN -1 /* Deprecated, please use VALKEYMODULE_POSTPONED_LEN */