Feature: Add Bolt12 Uniffi Type Wrappers by alexanderwiederin · Pull Request #542 · lightningdevkit/ldk-node

alexanderwiederin · 2025-05-19T09:55:50Z

Second PR for #504.

This PR adds full Offer-, Refund- and Bolt12Invoice- types for the FFI bindings.

Changes:

Type definitions in ldk_node.udl and uniffi_types.rs
Implementation of UniffiType trait to standardize conversions between LDK types and their FFI-compatible wrappers in uniffi_conversions.rs
Integration of wrapper types in payment handling methods in bolt12.rs and unified_qr.rs

Benefits:

Direct access to Offer, Refund and Bolt12Invoice properties from FFI languages
Consistent API across languages

Note:

Appreciate that this PR is big. Happy to break down into smaller parts if preferred.

ldk-reviews-bot · 2025-05-19T09:55:52Z

👋 Thanks for assigning @enigbe as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

tnull

Thanks, already looks pretty good! Did a first higher-level pass.

tnull

Cool, I like the proposed approach. Very clean!

Just a few comments.

ldk-reviews-bot · 2025-06-04T12:53:35Z

🔔 1st Reminder

Hey @enigbe! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

ldk-reviews-bot · 2025-06-07T00:00:48Z

🔔 2nd Reminder

Hey @enigbe! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

ldk-reviews-bot · 2025-06-09T00:01:39Z

🔔 3rd Reminder

Hey @enigbe! This PR has been waiting for your review.
Please take a look when you have a chance. If you're unable to review, please let us know so we can find another reviewer.

enigbe

Well done @alexanderwiederin,

I've reviewed this and just have a small question regarding fixed-sized arrays. The ffi/conversion approach looked good to me, but following your conversation with @tnull has highlighted some gaps in my understanding of Uniffi's internals especially with regards to heap allocation. I'll be looking into that further.

I've also tested this and it LGTM.

enigbe · 2025-06-09T14:15:08Z

+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum OfferAmount {
+	Bitcoin { amount_msats: u64 },
+	Currency { iso4217_code: String, amount: u64 },
+}


Curious about why LdkAmount is not used directly here. OfferAmount is basically the same struct except for the iso4217_code field. Is this because there is no support for fixed-sized arrays?

Yea, that's pretty much it. OfferAmount provides a binding-friendly representation by using String instead of a fixed-size byte array for iso4217_code. I also don't think you can automatically convert complex types across FFI language boundaries in general.

enigbe · 2025-06-09T17:22:47Z

+}
+
+#[cfg(feature = "uniffi")]
+pub fn maybe_wrap<T>(ldk_type: impl Into<T>) -> std::sync::Arc<T> {


Why is ldk_typeimpl Into<T> and not just T?

Good question! T is not actually the type that is passed to maybe_wrap. impl Into<T> means that the argument we pass to maybe_wrap can be any type that implements Into<T> to convert itself into T. In our case T would be the UniFFI type that is needed at the call site.
For example, we pass LDK native types (like lightning_invoice::Bolt11Invoice), which gets converted to their corresponding UniFFI wrapper type (like ffi::types::Bolt11Invoice) using .into() before being wrapped in an Arc.

tnull

LGTM I think, mod one nit.

Let me know if you intend to make further changes or if this can land from your side.

This commit reorganizes the FFI architecture by introducing conversion traits for lightning types. Moves code from uniffi_types.rs to a dedicated ffi module for separation of concerns.

alexanderwiederin · 2025-06-10T10:47:47Z

Thanks for the feedback @tnull. This can land from my side!

Implement Offer struct in ffi/types.rs to provide a wrapper around LDK's Offer for cross-language bindings. Modified payment handling in bolt12.rs to: - Support both native and FFI-compatible types via type aliasing - Implement conditional compilation for transparent FFI support - Update payment functions to handle wrapped types Added testing to verify that properties are preserved when wrapping/unwrapping between native and FFI types.

Implement Refund struct in ffi/types.rs to provide a wrapper around LDK's Refund for cross-language bindings. Modified payment handling in bolt12.rs to: - Support both native and FFI-compatible types via type aliasing - Implement conditional compilation for transparent FFI support - Update payment functions to handle wrapped types Added testing to verify that properties are preserved when wrapping/unwrapping between native and FFI types.

Implement Bolt12Invoice struct in ffi/types.rs to provide a wrapper around LDK's Bolt12Invoice for cross-language bindings. Modified payment handling in bolt12.rs to: - Support both native and FFI-compatible types via type aliasing - Implement conditional compilation for transparent FFI support - Update payment functions to handle wrapped types Added testing to verify that properties are preserved when wrapping/unwrapping between native and FFI types.

tnull

LGTM

alexanderwiederin commented May 19, 2025
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Comment threadsrc/uniffi_conversions.rs Outdated

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from f07aa51 to e85a185Compare May 20, 2025 19:25

alexanderwiederin marked this pull request as ready for review May 20, 2025 21:21

ldk-reviews-bot requested a review from valentinewallace May 20, 2025 21:22

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from e85a185 to 7188bcaCompare May 22, 2025 08:27

tnull requested review from tnull and removed request for valentinewallace May 22, 2025 15:13

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alexanderwiederin force-pushed the uniffi-bolt12-clean branch from 7188bca to 2f3bc2eCompare May 25, 2025 15:35

enigbe reviewed May 28, 2025
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tnull mentioned this pull request May 29, 2025
offers: parse invoice and invoice request lightningdevkit/rust-lightning#3800
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tnull reviewed May 29, 2025
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Comment threadsrc/uniffi_types.rs
Comment threadbindings/ldk_node.udl
Comment threadsrc/uniffi_types.rs
Comment threadsrc/uniffi_conversions.rs Outdated
Comment threadsrc/uniffi_conversions.rs Outdated

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from 670a885 to 2894d87Compare June 2, 2025 11:49

alexanderwiederin requested review from enigbe and tnull June 2, 2025 12:08

tnull mentioned this pull request Jun 3, 2025
Support passing preimage for spontaneous payments #549
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tnull reviewed Jun 3, 2025
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Comment threadsrc/ffi/conversions.rs Outdated
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Comment threadsrc/ffi/types.rs Outdated
Comment threadsrc/ffi/conversions.rs Outdated

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from 2894d87 to 3126d86Compare June 3, 2025 20:08

alexanderwiederin force-pushed the uniffi-bolt12-clean branch 4 times, most recently from 4a4572a to 1ebcb89Compare June 9, 2025 13:21

enigbe reviewed Jun 9, 2025
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tnull reviewed Jun 10, 2025
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Comment threadsrc/ffi/mod.rs Outdated

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from 1ebcb89 to affe664Compare June 10, 2025 09:56

Restructure FFI bindings with conversion traits for Lightning types
07b5471
This commit reorganizes the FFI architecture by introducing conversion traits for lightning types. Moves code from uniffi_types.rs to a dedicated ffi module for separation of concerns.

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from affe664 to 0dd04baCompare June 10, 2025 10:22

tnull reviewed Jun 10, 2025
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Comment threadbindings/ldk_node.udl

alexanderwiederin added 3 commits June 10, 2025 13:53

alexanderwiederin force-pushed the uniffi-bolt12-clean branch from 0dd04ba to f01d021Compare June 10, 2025 12:02

tnull approved these changes Jun 10, 2025
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tnull merged commit 40a3aeb into lightningdevkit:mainJun 10, 2025

This was referenced Jun 10, 2025
Expose proper Invoice / Offer types in bindings #504
Closed
Add support for sending to human-readable names (BIP 353) #528
Closed

joostjager mentioned this pull request Nov 19, 2025
Add draft changelog for LDK Node v0.7.0 #708
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alexanderwiederin commented May 19, 2025•
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