fix: simplified did_short_sig(), fixed elements check and now btc uses 330 sat for p2tr change outputs

Author: Andezion

bitcoin/tx.c

@@ -987,11 +987,13 @@ struct amount_sat change_amount(struct amount_sat excess, u32 feerate_perkw,
 	if (!amount_sat_sub(&excess, excess, fee))
 		return AMOUNT_SAT(0);
 
-	// Change is P2TR (Bitcoin) or P2WPKH (Elements) both have
-	// dust limit of 330 sat. Legacy types (P2PKH/P2SH) use 546 sat
-	// but we dont create those as change outputs 
-	if (!amount_sat_greater_eq(excess, AMOUNT_SAT(330)))
-		return AMOUNT_SAT(0);
+	if (chainparams->is_elements) {
+		if (!amount_sat_greater_eq(excess, AMOUNT_SAT(546)))
+			return AMOUNT_SAT(0);
+	} else {
+		if (!amount_sat_greater_eq(excess, AMOUNT_SAT(330)))
+			return AMOUNT_SAT(0);
+	}
 
 	return excess;
 }

tests/utils.py

@@ -675,11 +675,7 @@ def serialize_payload_final_tlv(amount_msat, delay, total_msat, blockheight, pay
 # I wish we could force libwally to use different entropy and thus force it to
 # create 71-byte sigs always!
 def did_short_sig(node):
-    try:
-        wait_for(lambda: node.daemon.is_in_log('overgrind: short signature length'), timeout=5)
-        return True
-    except (TimeoutError, ValueError):
-        return False
+    return node.daemon.is_in_log('overgrind: short signature length')
 
 
 def check_feerate(nodes, actual_feerate, expected_feerate):