pay: Factor out handling of waitsendpay errors from deciding what t…

…o do due to those errors.

plugins/pay.c

@@ -37,6 +37,10 @@ struct pay_attempt {
 	struct json_out *failure;
 	/* The non-failure result (NULL on failure) */
 	const char *result;
+	/* A string of a JSON error message from `waitsendpay`.
+	 * NULL if no failure from `waitsendpay`.
+	 */
+	const char *waitsendpay_err;
 };
 
 struct pay_status {
@@ -320,15 +324,31 @@ static struct command_result *next_routehint(struct command *cmd,
 				    "Could not find a route");
 }
 
-static struct command_result *waitsendpay_error(struct command *cmd,
-						const char *buf,
-						const jsmntok_t *error,
-						struct pay_command *pc)
+/* Perform handling in case of payment error. */
+static struct command_result *
+handle_payment_error(struct command *cmd,
+		     struct pay_command *pc)
 {
+	struct pay_attempt *attempt = current_attempt(pc);
+	const char *buf;
+	const jsmntok_t *error;
+	bool parse_valid;
 	const jsmntok_t *codetok, *failcodetok, *nodeidtok, *scidtok, *dirtok;
 	int code, failcode;
 	bool node_err = false;
 
+	assert(attempt->waitsendpay_err);
+	/* Make the error string temporary to this function.  */
+	buf = tal_steal(tmpctx, attempt->waitsendpay_err);
+	attempt->waitsendpay_err = NULL;
+	/* Re-parse the string.
+	 * This should succeed since it succeeded before.
+	 */
+	error = json_parse_input(tmpctx, buf, tal_count(buf) - 1,
+				 &parse_valid);
+	assert(parse_valid);
+	assert(error);
+
 	attempt_failed_tok(pc, "waitsendpay", buf, error);
 
 	codetok = json_get_member(buf, error, "code");
@@ -402,6 +422,23 @@ static struct command_result *waitsendpay_error(struct command *cmd,
 				 pc->excludes[tal_count(pc->excludes)-1]);
 }
 
+/* Save the `waitsendpay` error message for later processing by
+ * handle_payment_error.
+ */
+static struct command_result * waitsendpay_error(struct command *cmd,
+						 const char *buf,
+						 const jsmntok_t *error,
+						 struct pay_command *pc)
+{
+	struct pay_attempt *attempt = current_attempt(pc);
+
+	attempt->waitsendpay_err = tal_strndup(pc,
+					       buf + error->start,
+					       error->end - error->start);
+
+	return handle_payment_error(cmd, pc);
+}
+
 static struct command_result *waitsendpay_done(struct command *cmd,
 					       const char *buf,
 					       const jsmntok_t *result,
@@ -809,6 +846,7 @@ static struct command_result *start_pay_attempt(struct command *cmd,
 	attempt->result = NULL;
 	attempt->sendpay = false;
 	attempt->why = tal_vfmt(pc->ps, fmt, ap);
+	attempt->waitsendpay_err = NULL;
 	va_end(ap);
 
 	return execute_getroute(cmd, pc);