feat(lightning): add CLN NUT-15 MPP partial payment support

tests/lightning/conftest.py

@@ -0,0 +1,12 @@
+import pytest
+
+
+# Skip the global mint_server fixture for lightning-specific tests
+@pytest.fixture
+def mint_server():
+    yield None
+
+
+@pytest.fixture(scope="session")
+def mint():
+    yield None

tests/lightning/test_clnrest_mpp.py

@@ -0,0 +1,139 @@
+from unittest.mock import AsyncMock, Mock, patch
+
+import pytest
+from bolt11 import Bolt11
+
+from cashu.core.base import MeltQuote, MeltQuoteState, Unit
+from cashu.lightning.base import PaymentResult
+from cashu.lightning.clnrest import CLNRestWallet
+
+
+def create_melt_quote(
+    amount: int, unit: str = "msat", request: str = "lnbc10u1p0example"
+) -> MeltQuote:
+    return MeltQuote(
+        quote="quote_test_123",
+        method="bolt11",
+        request=request,
+        checking_id="checking_id_test",
+        unit=unit,
+        amount=amount,
+        fee_reserve=1000,
+        state=MeltQuoteState.unpaid,
+        created_time=None,
+        paid_time=None,
+    )
+
+
+@pytest.fixture
+def wallet(monkeypatch: pytest.MonkeyPatch) -> CLNRestWallet:
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.settings.mint_clnrest_url", "https://localhost:3010"
+    )
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.settings.mint_clnrest_rune", "test_rune"
+    )
+    monkeypatch.setattr("cashu.lightning.clnrest.settings.mint_clnrest_cert", False)
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.settings.mint_clnrest_enable_mpp", True
+    )
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.settings.mint_retry_exponential_backoff_base_delay", 1
+    )
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.settings.mint_retry_exponential_backoff_max_delay", 10
+    )
+
+    mock_client = Mock()
+    mock_client.post = AsyncMock()
+    monkeypatch.setattr(
+        "cashu.lightning.clnrest.httpx.AsyncClient", Mock(return_value=mock_client)
+    )
+
+    wallet = CLNRestWallet(unit=Unit.sat)
+    wallet.supports_mpp = True
+    return wallet
+
+
+@pytest.mark.asyncio
+async def test_mpp_detection_routes_to_partial(wallet: CLNRestWallet):
+    with patch("cashu.lightning.clnrest.decode") as mock_decode:
+        mock_invoice = Mock(spec=Bolt11)
+        mock_invoice.payment_hash = "hash789"
+        mock_invoice.amount_msat = 1000000
+        mock_decode.return_value = mock_invoice
+
+        wallet.client.post = AsyncMock(
+            return_value=Mock(
+                is_error=False,
+                json=lambda: {
+                    "payment_hash": "hash789",
+                    "payment_preimage": "preimage_mpp",
+                    "amount_sent_msat": 600100,
+                    "amount_msat": 600000,
+                    "status": "complete",
+                },
+            )
+        )
+
+        quote = create_melt_quote(amount=600000, unit="msat")
+        fee_limit_msat = 1000
+
+        result = await wallet.pay_invoice(quote, fee_limit_msat)
+
+        assert result.result == PaymentResult.SETTLED
+        assert result.preimage == "preimage_mpp"
+        call_data = wallet.client.post.call_args.kwargs["data"]
+        assert "partial_msat" in call_data, "partial_msat must be sent to CLN for MPP"
+        assert call_data["partial_msat"] == 600000
+
+
+@pytest.mark.asyncio
+async def test_mpp_disabled_returns_error(wallet: CLNRestWallet):
+    wallet.supports_mpp = False
+
+    with patch("cashu.lightning.clnrest.decode") as mock_decode:
+        mock_invoice = Mock(spec=Bolt11)
+        mock_invoice.payment_hash = "hash123"
+        mock_invoice.amount_msat = 1000000
+        mock_decode.return_value = mock_invoice
+
+        quote = create_melt_quote(amount=600000, unit="msat")
+
+        result = await wallet.pay_invoice(quote, 1000)
+
+        assert result.result == PaymentResult.FAILED
+        assert result.error_message is not None
+        assert "does not support MPP" in result.error_message
+
+
+@pytest.mark.asyncio
+async def test_full_payment_no_mpp(wallet: CLNRestWallet):
+    with patch("cashu.lightning.clnrest.decode") as mock_decode:
+        mock_invoice = Mock(spec=Bolt11)
+        mock_invoice.payment_hash = "full_payment_hash"
+        mock_invoice.amount_msat = 1000000
+        mock_decode.return_value = mock_invoice
+
+        quote = create_melt_quote(amount=1000000, unit="msat")
+
+        wallet.client.post = AsyncMock(
+            return_value=Mock(
+                is_error=False,
+                json=lambda: {
+                    "payment_hash": "full_payment_hash",
+                    "payment_preimage": "preimage123",
+                    "amount_sent_msat": 1000100,
+                    "amount_msat": 1000000,
+                    "status": "complete",
+                },
+            )
+        )
+
+        result = await wallet.pay_invoice(quote, 1000)
+
+        assert result.result == PaymentResult.SETTLED
+        assert result.preimage == "preimage123"
+        call_data = wallet.client.post.call_args.kwargs["data"]
+        assert "partial_msat" not in call_data, "partial_msat must not be sent for full payments"
+