Refactor amount checks and moved currency check

Modified check_amount_msats_for_quantity to trust
the user-provided msats amount and moved the currency
check to the InvoiceRequest parsing code.

Updated fails_creating_or_paying_for_offer_without_connected_peers
and fails_creating_invoice_request_without_blinded_reply_path
offers tests to use fiat amounts, bypassing insufficient liquidity
errors.

lightning/src/ln/offers_tests.rs

@@ -54,6 +54,7 @@ use crate::offers::invoice::Bolt12Invoice;
 use crate::offers::invoice_error::InvoiceError;
 use crate::offers::invoice_request::{InvoiceRequest, InvoiceRequestFields};
 use crate::offers::parse::Bolt12SemanticError;
+use crate::offers::offer::{Amount};
 use crate::onion_message::messenger::PeeledOnion;
 use crate::onion_message::offers::OffersMessage;
 use crate::onion_message::packet::ParsedOnionMessageContents;
@@ -1267,15 +1268,15 @@ fn fails_creating_or_paying_for_offer_without_connected_peers() {
 	reconnect_nodes(args);
 
 	let offer = alice.node
-		.create_offer_builder(Some(absolute_expiry)).unwrap()
-		.amount_msats(10_000_000)
-		.build().unwrap();
+		.create_offer_builder(None).unwrap()
+		.amount(Amount::Currency {iso4217_code: *b"USD", amount: 6_000})
+		.build_unchecked();
 
 	let payment_id = PaymentId([1; 32]);
 
 	match david.node.pay_for_offer(&offer, None, None, None, payment_id, Retry::Attempts(0), None) {
 		Ok(_) => panic!("Expected error"),
-		Err(e) => assert_eq!(e, Bolt12SemanticError::InsufficientLiquidity),
+		Err(e) => assert_eq!(e, Bolt12SemanticError::MissingPaths),
 	}
 
 	assert!(nodes[0].node.list_recent_payments().is_empty());
@@ -1431,14 +1432,15 @@ fn fails_creating_invoice_request_without_blinded_reply_path() {
 
 	let offer = alice.node
 		.create_offer_builder(None).unwrap()
-		.amount_msats(10_000_000)
-		.build().unwrap();
+		.amount(Amount::Currency {iso4217_code: *b"USD", amount: 6_000})
+		.build_unchecked();
+
 
 	let payment_id = PaymentId([1; 32]);
 
 	match david.node.pay_for_offer(&offer, None, None, None, payment_id, Retry::Attempts(0), None) {
 		Ok(_) => panic!("Expected error"),
-		Err(e) => assert_eq!(e, Bolt12SemanticError::InsufficientLiquidity),
+		Err(e) => assert_eq!(e, Bolt12SemanticError::MissingPaths),
 	}
 
 	assert!(nodes[0].node.list_recent_payments().is_empty());

lightning/src/offers/invoice_request.rs

@@ -72,7 +72,7 @@ use crate::ln::inbound_payment::{ExpandedKey, IV_LEN, Nonce};
 use crate::ln::msgs::DecodeError;
 use crate::offers::invoice::BlindedPayInfo;
 use crate::offers::merkle::{SignError, SignFn, SignatureTlvStream, SignatureTlvStreamRef, TaggedHash, self};
-use crate::offers::offer::{Offer, OfferContents, OfferId, OfferTlvStream, OfferTlvStreamRef};
+use crate::offers::offer::{Amount, Offer, OfferContents, OfferId, OfferTlvStream, OfferTlvStreamRef};
 use crate::offers::parse::{Bolt12ParseError, ParsedMessage, Bolt12SemanticError};
 use crate::offers::payer::{PayerContents, PayerTlvStream, PayerTlvStreamRef};
 use crate::offers::signer::{Metadata, MetadataMaterial};
@@ -1131,7 +1131,15 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 		}
 
 		offer.check_quantity(quantity)?;
-		offer.check_amount_msats_for_quantity(amount, quantity)?;
+
+		let amount_msats = match offer.amount() {
+			None => amount,
+			Some(Amount::Bitcoin { amount_msats }) => Some(amount_msats),
+			Some(Amount::Currency { iso4217_code: _ , amount: _ }) => {
+				return Err(Bolt12SemanticError::UnsupportedCurrency)
+			},
+		};
+		offer.check_amount_msats_for_quantity(amount_msats, quantity)?;
 
 		let features = features.unwrap_or_else(InvoiceRequestFeatures::empty);
 

lightning/src/offers/offer.rs

@@ -309,7 +309,7 @@ macro_rules! offer_builder_methods { (
 	/// Sets the [`Offer::amount`].
 	///
 	/// Successive calls to this method will override the previous setting.
-	pub(super) fn amount($($self_mut)* $self: $self_type, amount: Amount) -> $return_type {
+	pub(crate) fn amount($($self_mut)* $self: $self_type, amount: Amount) -> $return_type {
 		$self.offer.amount = Some(amount);
 		$return_value
 	}
@@ -453,7 +453,7 @@ macro_rules! offer_builder_test_methods { (
 	}
 
 	#[cfg_attr(c_bindings, allow(dead_code))]
-	pub(super) fn build_unchecked($self: $self_type) -> Offer {
+	pub(crate) fn build_unchecked($self: $self_type) -> Offer {
 		$self.build_without_checks()
 	}
 } }
@@ -854,11 +854,7 @@ impl OfferContents {
 	pub(super) fn check_amount_msats_for_quantity(
 		&self, amount_msats: Option<u64>, quantity: Option<u64>
 	) -> Result<(), Bolt12SemanticError> {
-		let offer_amount_msats = match self.amount {
-			None => 0,
-			Some(Amount::Bitcoin { amount_msats }) => amount_msats,
-			Some(Amount::Currency { .. }) => return Err(Bolt12SemanticError::UnsupportedCurrency),
-		};
+		let offer_amount_msats = amount_msats.unwrap_or(0);
 
 		if !self.expects_quantity() || quantity.is_some() {
 			let expected_amount_msats = offer_amount_msats.checked_mul(quantity.unwrap_or(1))