Refresh async static invoices after channel changes

[shaavan]

Refresh async receive static invoices when local channel state changes, so
already-published async offers do not keep serving stale payment paths until the
normal refresh threshold.

This adds a forced refresh path for cached async receive offers:

• selects used and pending offers for immediate static invoice refresh
• reuses the existing static invoice construction flow
• marks refresh needed when channels become ready, close, or local fee updates
  are queued
• defers the actual refresh until after channel locks are released

Ready unused offers are left to the existing offer rotation path because they
have not been returned to the application yet.

Summary by CodeRabbit

• New Features

  • Async receive offer static-invoice refresh now supports both timer-based and forced refresh flows when channel conditions change.
  • Channel readiness and channel lifecycle events can trigger refreshed static invoice generation, including for offers already marked used.

• Bug Fixes

  • Deferred refresh logic ensures cached static invoices are rebuilt only after relevant channel state updates complete.
  • Refresh selection now better targets offers needing immediate forced invoice updates after local channel changes.

• Tests

  • Added coverage for refreshed static invoices when channels open and used-offer scenarios.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 23600034-c4bf-4642-88c0-a7fe9d96d4c5

📥 Commits

Reviewing files that changed from the base of the PR and between c7a7887 and 5f3f1f0.

📒 Files selected for processing (1)

• lightning/src/ln/async_payments_tests.rs

📝 Walkthrough

Walkthrough

The PR adds forced async receive static-invoice refreshes on channel-state changes, coordinates pending refreshes in ChannelManager, and adds a test that verifies refreshed invoices after a new channel opens.

Changes

Async receive static invoice refresh

Layer / File(s)	Summary
Forced refresh selection lightning/src/offers/async_receive_offer_cache.rs, lightning/src/offers/flow.rs	OffersMessageFlow now distinguishes forced and timer-driven static-invoice refreshes and builds ServeStaticInvoice messages from the selected cached offers.
Pending refresh plumbing lightning/src/ln/channelmanager.rs	ChannelManager adds an atomic pending-refresh flag, initializes it in construction paths, and adds helpers to trigger or process the forced refresh flow.
Channel-ready and fee triggers lightning/src/ln/channelmanager.rs	Initial channel-ready emission and fee-update handling now mark static-invoice refreshes pending and process them after the state update.
Lifecycle and message triggers lightning/src/ln/channelmanager.rs	Shutdown, close, splice, discarded-funding, and inbound channel message handlers now route pending static-invoice refresh processing after their internal handling.
Channel-open refresh test lightning/src/ln/async_payments_tests.rs	A helper extracts pending ServeStaticInvoice onion messages, and a test verifies refreshed invoices are sent and persisted when a new channel opens.

Sequence Diagram(s)

sequenceDiagram
  participant ChannelManager
  participant OffersMessageFlow
  participant AsyncReceiveOfferCache
  participant Recipient
  participant StaticInvoiceServer
  ChannelManager->>OffersMessageFlow: process_pending_async_receive_static_invoice_refresh()
  OffersMessageFlow->>AsyncReceiveOfferCache: offers_needing_forced_invoice_refresh()
  OffersMessageFlow->>Recipient: ServeStaticInvoice
  Recipient->>StaticInvoiceServer: deliver ServeStaticInvoice
  StaticInvoiceServer->>StaticInvoiceServer: PersistStaticInvoice

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Poem

A bunny hopped by channel light,
With invoices fresh and tails all bright.
Pending flags went boing, then clear,
New refreshes sprouted far and near.
Crunch, crunch — the static stars align 🐰

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: forcing async static invoice refreshes when channel state changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch static-update-review

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@lightning/src/ln/async_payments_tests.rs`:
- Around line 433-434: The extractor in async_payments_tests should ignore
OfferPathsRequest instead of rejecting every message, since this refresh path
can queue a server-bound path request before ServeStaticInvoice. Update the call
to extract_expected_om to use a predicate that filters out
AsyncPaymentsMessage::OfferPathsRequest while still matching the expected
invoice-related message, so the test follows the same construction flow used
elsewhere in the file.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f8f507a7-f4a9-48e0-8076-4e87cdb9b6eb

📥 Commits

Reviewing files that changed from the base of the PR and between 9df5c9d and a945650.

📒 Files selected for processing (4)

• lightning/src/ln/async_payments_tests.rs
• lightning/src/ln/channelmanager.rs
• lightning/src/offers/async_receive_offer_cache.rs
• lightning/src/offers/flow.rs