mfc: add a 'fail_destination' helper

Caches state at which we failed + sets error

plugins/spender/multifundchannel.c

@@ -564,9 +564,7 @@ connect_err(struct command *cmd,
 			   json_tok_full_len(code_tok),
 			   json_tok_full(buf, code_tok));
 
-	dest->state = MULTIFUNDCHANNEL_CONNECT_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(mfc, buf, error);
-
 	return connect_done(dest);
 }
 
@@ -1110,9 +1108,7 @@ fundchannel_start_err(struct command *cmd,
 	completed, we can then fail.
 	*/
 
-	dest->state = MULTIFUNDCHANNEL_START_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(dest->mfc, buf, error);
-
 	return fundchannel_start_done(dest);
 }
 
@@ -1408,9 +1404,7 @@ fundchannel_complete_err(struct command *cmd,
 			   json_tok_full_len(error),
 			   json_tok_full(buf, error));
 
-	dest->state = MULTIFUNDCHANNEL_COMPLETE_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(mfc, buf, error);
-
 	return fundchannel_complete_done(dest);
 }
 
@@ -1706,6 +1700,17 @@ static bool dest_failed(struct multifundchannel_destination *dest)
 	abort();
 }
 
+void fail_destination(struct multifundchannel_destination *dest,
+		      char *error TAKES)
+{
+	dest->fail_state = dest->state;
+	dest->state = MULTIFUNDCHANNEL_FAILED;
+	if (taken(error))
+		dest->error = tal_steal(dest->mfc, error);
+	else
+		dest->error = tal_strdup(dest->mfc, error);
+}
+
 /* Filter the failing destinations.  */
 static struct command_result *
 post_cleanup_redo_multifundchannel(struct multifundchannel_redo *redo)

plugins/spender/multifundchannel.h

@@ -71,6 +71,9 @@ struct multifundchannel_destination {
 	*/
 	enum multifundchannel_state state;
 
+	/* Last known state before failure */
+	enum multifundchannel_state fail_state;
+
 	/* the actual target script and address.  */
 	const u8 *funding_script;
 	const char *funding_addr;
@@ -213,6 +216,11 @@ mfc_forward_error(struct command *cmd,
 		  const char *buf, const jsmntok_t *error,
 		  struct multifundchannel_command *);
 
+/* When a destination fails, we record the furthest state
+ * reached, and the error message for the failure */
+void fail_destination(struct multifundchannel_destination *dest,
+		      char *error TAKES);
+
 /* Use this instead of command_finished.  */
 struct command_result *
 mfc_finished(struct multifundchannel_command *, struct json_stream *response);

plugins/spender/openchannel.c

@@ -2,6 +2,7 @@
 #include <bitcoin/psbt.h>
 #include <ccan/ccan/array_size/array_size.h>
 #include <ccan/ccan/cast/cast.h>
+#include <ccan/ccan/tal/str/str.h>
 #include <common/json_stream.h>
 #include <common/psbt_open.h>
 #include <common/type_to_string.h>
@@ -455,8 +456,7 @@ openchannel_signed_err(struct command *cmd,
 			   json_tok_full_len(code_tok),
 			   json_tok_full(buf, code_tok));
 
-	dest->state = MULTIFUNDCHANNEL_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(dest->mfc, buf, error);
 	return after_openchannel_signed(mfc);
 }
 
@@ -808,9 +808,7 @@ openchannel_update_err(struct command *cmd,
 			   json_tok_full_len(error),
 			   json_tok_full(buf, error));
 
-	dest->state = MULTIFUNDCHANNEL_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(mfc, buf, error);
-
 	return openchannel_update_returned(dest);
 }
 
@@ -1025,8 +1023,9 @@ openchannel_init_ok(struct command *cmd,
 	/* Port any updates onto 'parent' PSBT */
 	if (!update_parent_psbt(dest->mfc, dest, dest->psbt,
 				dest->updated_psbt, &mfc->psbt)) {
-		dest->state = MULTIFUNDCHANNEL_FAILED;
+		fail_destination(dest,
-		dest->error = "Unable to update parent with node's PSBT";
+				 take(tal_fmt(NULL, "Unable to update parent"
+					      " with node's PSBT")));
 	}
 
 	/* Clone updated-psbt to psbt, so original changeset
@@ -1069,9 +1068,7 @@ openchannel_init_err(struct command *cmd,
 			   json_tok_full_len(code_tok),
 			   json_tok_full(buf, code_tok));
 
-	dest->state = MULTIFUNDCHANNEL_START_FAILED;
+	fail_destination(dest, take(json_strdup(NULL, buf, error)));
-	dest->error = json_strdup(dest->mfc, buf, error);
-
 	return openchannel_init_done(dest);
 }