jsonrpc: Accomodate some pedantic JSON-RPC impls

The JSON-RPC was non-standard compliant in that it omitted the required
`jsonrpc` entry and it was returning both `error` as well as
`result`. This fixes both of these issues.

daemon/jsonrpc.c

@@ -353,12 +353,18 @@ static void json_result(struct json_connection *jcon,
 			const char *id, const char *res, const char *err)
 {
 	struct json_output *out = tal(jcon, struct json_output);
-
+	if (err == NULL)
+		out->json = tal_fmt(out,
+				    "{ \"jsonrpc\": \"2.0\", "
+				    "\"result\" : %s,"
+				    " \"id\" : %s }\n",
+				    res, id);
+	else
 		out->json = tal_fmt(out,
-			    "{ \"result\" : %s,"
+				    "{ \"jsonrpc\": \"2.0\", "
 				    " \"error\" : %s,"
 				    " \"id\" : %s }\n",
-			    res, err, id);
+				    err, id);
 
 	/* Queue for writing, and wake writer (and maybe reader). */
 	list_add_tail(&jcon->output, &out->list);
@@ -386,7 +392,7 @@ void command_success(struct command *cmd, struct json_result *result)
 		return;
 	}
 	assert(jcon->current == cmd);
-	json_result(jcon, cmd->id, json_result_string(result), "null");
+	json_result(jcon, cmd->id, json_result_string(result), NULL);
 	log_debug(jcon->log, "Success");
 	jcon->current = tal_free(cmd);
 }
@@ -418,7 +424,7 @@ void command_fail(struct command *cmd, const char *fmt, ...)
 	quote = tal_fmt(cmd, "\"%s\"", error);
 
 	assert(jcon->current == cmd);
-	json_result(jcon, cmd->id, "null", quote);
+	json_result(jcon, cmd->id, NULL, quote);
 	jcon->current = tal_free(cmd);
 }
 
@@ -426,7 +432,7 @@ static void json_command_malformed(struct json_connection *jcon,
 				   const char *id,
 				   const char *error)
 {
-	return json_result(jcon, id, "null", error);
+	return json_result(jcon, id, NULL, error);
 }
 
 static void parse_request(struct json_connection *jcon, const jsmntok_t tok[])

daemon/lightning-cli.c

@@ -128,7 +128,7 @@ int main(int argc, char *argv[])
 			tal_resize(&resp, tal_count(resp) * 2);
 
 		/* parsing huge outputs is slow: do quick check first. */
-		if (num_opens == num_closes && strstr(resp, "\"result\""))
+		if (num_opens == num_closes)
 			break;
 	}
 	if (i < 0)
@@ -158,13 +158,10 @@ int main(int argc, char *argv[])
 		     "Non-object response '%s'", resp);
 
 	result = json_get_member(resp, toks, "result");
-	if (!result)
-		errx(ERROR_TALKING_TO_LIGHTNINGD,
-		     "Missing 'result' in response '%s'", resp);
 	error = json_get_member(resp, toks, "error");
-	if (!error)
+	if (!error && !result)
 		errx(ERROR_TALKING_TO_LIGHTNINGD,
-		     "Missing 'error' in response '%s'", resp);
+		     "Either 'result' or 'error' must be returned in response '%s'", resp);
 	id = json_get_member(resp, toks, "id");
 	if (!id)
 		errx(ERROR_TALKING_TO_LIGHTNINGD,
@@ -174,7 +171,7 @@ int main(int argc, char *argv[])
 		     "Incorrect 'id' in response: %.*s",
 		     json_tok_len(id), json_tok_contents(resp, id));
 
-	if (json_tok_is_null(resp, error)) {
+	if (!error || json_tok_is_null(resp, error)) {
 		printf("%.*s\n",
 		       json_tok_len(result),
 		       json_tok_contents(resp, result));