Note that abandon_payment does not persist the state update in docs

If a user calls `abandon_payment`, then restarts without freshly
persisting the `ChannelManager`, the payment will still be pending
on restart. This was unclear from the docs (and the docs seemed to
imply otherwise). Because this doesn't materially impact the
usability of `abandon_payment` (users shouldn't be called
`retry_payment` on an abandoned one anyway), we simply document it.

Fixes #1804.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index bb99b02d9f9a90bdafee770671100a22a95e2e70..29304cadb5516fdc4f103e694ca5656af56b6e31 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -2761,15 +2761,21 @@ impl<M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelManager<M, T, K, F
 
        /// Signals that no further retries for the given payment will occur.
        ///
-       /// After this method returns, any future calls to [`retry_payment`] for the given `payment_id`
-       /// will fail with [`PaymentSendFailure::ParameterError`]. If no such event has been generated,
-       /// an [`Event::PaymentFailed`] event will be generated as soon as there are no remaining
-       /// pending HTLCs for this payment.
+       /// After this method returns, no future calls to [`retry_payment`] for the given `payment_id`
+       /// are allowed. If no [`Event::PaymentFailed`] event had been generated before, one will be
+       /// generated as soon as there are no remaining pending HTLCs for this payment.
        ///
        /// Note that calling this method does *not* prevent a payment from succeeding. You must still
        /// wait until you receive either a [`Event::PaymentFailed`] or [`Event::PaymentSent`] event to
        /// determine the ultimate status of a payment.
        ///
+       /// If an [`Event::PaymentFailed`] event is generated and we restart without this
+       /// [`ChannelManager`] having been persisted, the payment may still be in the pending state
+       /// upon restart. This allows further calls to [`retry_payment`] (and requiring a second call
+       /// to [`abandon_payment`] to mark the payment as failed again). Otherwise, future calls to
+       /// [`retry_payment`] will fail with [`PaymentSendFailure::ParameterError`].
+       ///
+       /// [`abandon_payment`]: Self::abandon_payment
        /// [`retry_payment`]: Self::retry_payment
        /// [`Event::PaymentFailed`]: events::Event::PaymentFailed
        /// [`Event::PaymentSent`]: events::Event::PaymentSent

diff --git a/pending_changelog/matt-abandon-restart.txt b/pending_changelog/matt-abandon-restart.txt
new file mode 100644 (file)
index 0000000..07dc073
--- /dev/null
+++ b/pending_changelog/matt-abandon-restart.txt
@@ -0,0 +1,4 @@
+## API Updates
+- `ChannelManager::abandon_payment` docs have been updated to note that the
+  payment may return to pending after a restart if no persistence occurs. This
+  is not a change in behavior - ensure your existing code is safe.