Add new RM_Call flags for script mode, no writes, and error replies. (#10372)

The PR extends RM_Call with 3 new capabilities using new flags that
are given to RM_Call as part of the `fmt` argument.
It aims to assist modules that are getting a list of commands to be
executed from the user (not hard coded as part of the module logic),
think of a module that implements a new scripting language...

* `S` - Run the command in a script mode, this means that it will raise an
  error if a command which are not allowed inside a script (flaged with the
  `deny-script` flag) is invoked (like SHUTDOWN). In addition, on script mode,
  write commands are not allowed if there is not enough good replicas (as
  configured with `min-replicas-to-write`) and/or a disk error happened.

* `W` - no writes mode, Redis will reject any command that is marked with `write`
  flag. Again can be useful to modules that implement a new scripting language
  and wants to prevent any write commands.

* `E` - Return errors as RedisModuleCallReply. Today the errors that happened
  before the command was invoked (like unknown commands or acl error) return
  a NULL reply and set errno. This might be missing important information about
  the failure and it is also impossible to just pass the error to the user using
  RM_ReplyWithCallReply. This new flag allows you to get a RedisModuleCallReply
  object with the relevant error message and treat it as if it was an error that was
  raised by the command invocation.

Tests were added to verify the new code paths.

In addition small refactoring was done to share some code between modules,
scripts, and `processCommand` function:
1. `getAclErrorMessage` was added to `acl.c` to unified to log message extraction
  from the acl result
2. `checkGoodReplicasStatus` was added to `replication.c` to check the status of
  good replicas. It is used on `scriptVerifyWriteCommandAllow`, `RM_Call`, and
  `processCommand`.
3. `writeCommandsGetDiskErrorMessage` was added to `server.c` to get the error
  message on persistence failure. Again it is used on `scriptVerifyWriteCommandAllow`,
  `RM_Call`, and `processCommand`.

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/modules/basics.c b/tests/modules/basics.c
index 4d639d682..ecd1b8852 100644
--- a/tests/modules/basics.c
+++ b/tests/modules/basics.c
@@ -718,6 +718,25 @@ end:
 
 /* Return 1 if the reply matches the specified string, otherwise log errors
  * in the server log and return 0. */
+int TestAssertErrorReply(RedisModuleCtx *ctx, RedisModuleCallReply *reply, char *str, size_t len) {
+    RedisModuleString *mystr, *expected;
+    if (RedisModule_CallReplyType(reply) != REDISMODULE_REPLY_ERROR) {
+        return 0;
+    }
+
+    mystr = RedisModule_CreateStringFromCallReply(reply);
+    expected = RedisModule_CreateString(ctx,str,len);
+    if (RedisModule_StringCompare(mystr,expected) != 0) {
+        const char *mystr_ptr = RedisModule_StringPtrLen(mystr,NULL);
+        const char *expected_ptr = RedisModule_StringPtrLen(expected,NULL);
+        RedisModule_Log(ctx,"warning",
+            "Unexpected Error reply reply '%s' (instead of '%s')",
+            mystr_ptr, expected_ptr);
+        return 0;
+    }
+    return 1;
+}
+
 int TestAssertStringReply(RedisModuleCtx *ctx, RedisModuleCallReply *reply, char *str, size_t len) {
     RedisModuleString *mystr, *expected;
 
@@ -846,6 +865,18 @@ int TestBasics(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     if (!TestAssertStringReply(ctx,RedisModule_CallReplyArrayElement(reply, 0),"test",4)) goto fail;
     if (!TestAssertStringReply(ctx,RedisModule_CallReplyArrayElement(reply, 1),"1234",4)) goto fail;
 
+    T("foo", "E");
+    if (!TestAssertErrorReply(ctx,reply,"ERR Unknown Redis command 'foo'.",32)) goto fail;
+
+    T("set", "Ec", "x");
+    if (!TestAssertErrorReply(ctx,reply,"ERR Wrong number of args calling Redis command 'set'.",53)) goto fail;
+
+    T("shutdown", "SE");
+    if (!TestAssertErrorReply(ctx,reply,"ERR command 'shutdown' is not allowed on script mode",52)) goto fail;
+
+    T("set", "WEcc", "x", "1");
+    if (!TestAssertErrorReply(ctx,reply,"ERR Write command 'set' was called while write is not allowed.",62)) goto fail;
+
     RedisModule_ReplyWithSimpleString(ctx,"ALL TESTS PASSED");
     return REDISMODULE_OK;