Bindings by crodas · Pull Request #1706 · cashubtc/cdk

crodas · 2026-03-06T04:59:23Z

Description

Prototype to have a monorepo for all the bindings

Closes: #1539, #1670

Notes to the reviewers

Suggested CHANGELOG Updates

CHANGED

ADDED

REMOVED

FIXED

Checklist

I followed the code style guidelines
I ran just final-check before committing

thesimplekid

Nice. I think this is generally in the right direction though I didn't try to run anything.

thesimplekid · 2026-03-06T08:01:38Z

bindings/swift/generate-bindings.sh

+# Install targets if needed
+echo "📦 Ensuring Rust targets are installed..."
+rustup target add aarch64-apple-ios
+rustup target add x86_64-apple-ios
+rustup target add aarch64-apple-ios-sim
+rustup target add aarch64-apple-darwin
+rustup target add x86_64-apple-darwin


We need to define this in a nix and not use rustup

thesimplekid · 2026-03-06T08:04:06Z

bindings/dart/flutter_example/lib/main.dart

I think this flutter example should live else where. We should not commit a full flutter example to the cdk repo. Instead we should have a more basic just dart example/test.

thesimplekid · 2026-03-06T08:05:41Z

bindings/swift/Sources/Cdk/CashuDevKit.swift

I don't think we should commit generated files and they should be added to .gitignore

crates/cdk-ffi/Cargo.toml

thesimplekid · 2026-03-06T08:12:30Z

bindings/dart/generate-bindings.sh

For this to work in ci we'll need to add a new shell to the flake that has dart available.

https://github.com/cashubtc/cdk-flutter/blob/master/flake.nix

thesimplekid · 2026-03-06T08:15:52Z

bindings/swift/generate-bindings.sh

+echo "📦 Ensuring Rust targets are installed..."
+rustup target add aarch64-apple-ios
+rustup target add x86_64-apple-ios
+rustup target add aarch64-apple-ios-sim
+rustup target add aarch64-apple-darwin
+rustup target add x86_64-apple-darwin
+
+# Set cross-compilation toolchain for Apple targets when building on Linux.
+# cc-rs (used by build scripts like secp256k1-sys) picks CC_<target> to find the C compiler.
+# Without these it falls back to the host "cc" (Linux GCC) which doesn't understand
+# -arch or -mmacosx-version-min flags.
+if [[ "$(uname)" == "Linux" ]]; then
+    OSXCROSS_BIN=/usr/local/osxcross/bin
+    DARWIN_TRIPLE=aarch64-apple-darwin24.4
+    DARWIN_X86_TRIPLE=x86_64-apple-darwin24.4
+    IOS_SDK=/usr/local/ios-sdk/iPhoneOS18.4.sdk
+    IOS_SIM_SDK=/usr/local/ios-sdk/iPhoneSimulator18.4.sdk
+
+    export CC_aarch64_apple_darwin=$OSXCROSS_BIN/$DARWIN_TRIPLE-clang
+    export AR_aarch64_apple_darwin=$OSXCROSS_BIN/$DARWIN_TRIPLE-ar
+    export CC_x86_64_apple_darwin=$OSXCROSS_BIN/$DARWIN_X86_TRIPLE-clang
+    export AR_x86_64_apple_darwin=$OSXCROSS_BIN/$DARWIN_X86_TRIPLE-ar
+
+    # iOS: use system clang, NOT the osxcross darwin wrapper.
+    # The osxcross darwin wrapper unconditionally adds -mmacosx-version-min, which
+    # conflicts with -miphoneos-version-min that cc-rs adds for iOS targets.
+    export CC_aarch64_apple_ios=/usr/bin/clang
+    export AR_aarch64_apple_ios=$OSXCROSS_BIN/$DARWIN_TRIPLE-ar
+    export CFLAGS_aarch64_apple_ios="-isysroot $IOS_SDK -target arm64-apple-ios14.0"
+
+    export CC_aarch64_apple_ios_sim=/usr/bin/clang
+    export AR_aarch64_apple_ios_sim=$OSXCROSS_BIN/$DARWIN_TRIPLE-ar
+    export CFLAGS_aarch64_apple_ios_sim="-isysroot $IOS_SIM_SDK -target arm64-apple-ios14.0-simulator"
+
+    export CC_x86_64_apple_ios=/usr/bin/clang
+    export AR_x86_64_apple_ios=$OSXCROSS_BIN/$DARWIN_X86_TRIPLE-ar
+    export CFLAGS_x86_64_apple_ios="-isysroot $IOS_SIM_SDK -target x86_64-apple-ios14.0-simulator"


Should define this in a flake and not use rustup

thesimplekid · 2026-03-06T08:17:27Z

bindings/README.md

+# CDK Bindings
+
+This part of the project is heavily inspired by [Bark Bindings][1],
+particularly its model for exporting a Rust codebase through FFI and making it
+accessible from other languages.
+
+The purpose of this project is to expose the CDK Wallet and its associated
+traits so they can be consumed in target languages as abstract classes or
+interfaces. This enables developers to extend or implement language-specific
+functionality while relying on the shared Rust core.
+
+A separate crate is provided for each target language. These crates serve as
+integration layers where Rust code can be adapted to the conventions and native
+capabilities of each platform or language runtime.
+
+[1]: https://gitlab.com/ark-bitcoin/bark-ffi-bindings


Should make this more what it is and how to use it and when we need to modify it. We can credit bark at the end of the readme.

thesimplekid · 2026-03-06T08:25:30Z

crates/cdk-ffi/src/database.rs


+/// Unified wallet storage: either a built-in Rust backend or a custom
+/// foreign-language implementation of the `WalletDatabase` callback interface.
+#[derive(uniffi::Enum)]


We use the enum because of a uniffi limitation of being able to use a trait directly, I'm guessing? Can we just add a comment explaining that?

Should we add some constructors on the enum, new_sqlite(path), new_psgl(url) for example? Think that would be easier for downstream to use.

We use the enum because of a uniffi limitation of being able to use a trait directly, I'm guessing? Can we just add a comment explaining that?

Yeah, I'll expand on that. But that is the reason

thesimplekid · 2026-03-06T08:28:24Z

bindings/dart/rust/uniffi-bindgen.rs

+    patch_generated(&generated_path);
+}
+
+/// Patches the generated cdk_ffi.dart to fix uniffi-dart codegen issues.


Can we just add a little more detail on why we need to patch and if it might change in the future as I understand this is required but it could be fragile, so to save us some time debugging in the future. Also if we could track what we need in order to avoid patching to get the upstream that would be great.

thesimplekid · 2026-03-06T08:30:33Z

bindings/dart/rust/Cargo.toml

+[dependencies]
+cdk-ffi.workspace = true
+uniffi = { version = "=0.30.0", features = ["cli"] }
+uniffi-dart = { git = "https://github.com/Uniffi-Dart/uniffi-dart" }


We should pick a tag, looks like payjoin is using v0.1.0+v0.30.0, do we need main. If so whatever commit is working for us.

thesimplekid · 2026-03-11T11:57:05Z

I notice the flake.lock is not changed after adding the dart overlay. This could be what is causing the rate limiting as this needs to be updated. nix flake lock should be run and the new lock file committed.

thesimplekid · 2026-03-11T14:22:11Z

bindings/dart/lib/src/generated/cdk_ffi.dart

I think generated files should not be commited.

I think it should, at least people do that in other repos.

thesimplekid · 2026-03-11T14:25:45Z

Package.swift

Does this need to be at the root level?

Introduce Dart/Flutter bindings generated via uniffi-dart, including: - Flutter example wallet app with mint, send, and receive flows - WalletStore enum (Sqlite/Postgres/Custom) replacing separate constructors, allowing both built-in Rust backends and foreign callback implementations through a single `new()` constructor - Justfile targets for building and running Dart bindings - Post-generation patches for uniffi-dart codegen issues

- Add Swift binding generation via UniFFI for iOS, iOS Simulator, and macOS - Include generate-bindings.sh script that builds universal XCFramework with support for aarch64-apple-ios, aarch64-apple-ios-sim, and aarch64-apple-darwin targets - Add Swift wrapper (CashuDevKit.swift) generated from cdk-ffi crate - Add Swift example project demonstrating wallet creation, minting, melting, and multi-mint wallet usage - Include Info.plist resources for iOS, iOS Simulator, and macOS frameworks - Add UniFFI bindgen configuration (uniffi.toml) and Swift bindgen binary - Update justfile with swift-bindings and swift-example tasks - Update Dart bindings: regenerate FFI bindings, add generate-bindings.sh, update flutter_example dependencies - Bump cdk-ffi uniffi dependency to version 0.29

- Consolidate uniffi version (0.30) in workspace root Cargo.toml - Replace per-crate version pins with workspace = true in cdk-ffi, cdk-ffi-swift, and cdk-ffi-dart - Apply rustfmt formatting to dart bindings codegen and FFI sources - Update Cargo.lock.msrv with resolved dependency versions

- Remove the Flutter example app and Swift example app - Add Dart unit tests (wallet_test.dart) and Swift tests (CdkTests.swift) that verify wallet initialization, zero balance, and mint flow against testnut.cashu.space - Add CI jobs for Dart and Swift binding tests on self-hosted/macOS runners - Add nix `bindings` devShell with Dart SDK, OpenSSL, and stable Rust toolchain (including Apple cross-compile targets) - Fix Dart build hook to forward full parent environment to cargo and extract OpenSSL paths from NIX_CFLAGS_COMPILE/NIX_LDFLAGS as fallback - Update justfile: replace `example-dart`/`example-swift` with `test-dart`/`test-swift` recipes

thesimplekid · 2026-03-18T15:32:08Z

bindings/swift/Tests/CdkTests.swift

+        let tempDir = FileManager.default.temporaryDirectory
+        dbPath = tempDir.appendingPathComponent(UUID().uuidString + ".sqlite").path
+        wallet = try Wallet(
+            mintUrl: "https://testnut.cashu.space",


Suggested change

mintUrl: "https://testnut.cashu.space",

mintUrl: "https://testnut.cashudevkit.org",

github-project-automation bot added this to CDK Mar 6, 2026

github-project-automation bot moved this to Backlog in CDK Mar 6, 2026

thesimplekid reviewed Mar 6, 2026

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crodas force-pushed the feature/bindings branch 7 times, most recently from ec78b29 to 6199ed5 Compare March 10, 2026 14:53

thesimplekid reviewed Mar 11, 2026

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crodas force-pushed the feature/bindings branch from 6199ed5 to fc1ff7f Compare March 13, 2026 00:20

thesimplekid mentioned this pull request Mar 13, 2026

Add Dart Bindings Support #1171

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2 tasks

crodas force-pushed the feature/bindings branch 3 times, most recently from 8df4da8 to 67b7988 Compare March 16, 2026 22:33

crodas self-assigned this Mar 16, 2026

crodas force-pushed the feature/bindings branch 7 times, most recently from b2c5e77 to 497e283 Compare March 17, 2026 22:43

crodas added 5 commits March 18, 2026 07:17

Testing swift CI

2adf0f4

crodas force-pushed the feature/bindings branch from 497e283 to 2adf0f4 Compare March 18, 2026 14:44

thesimplekid reviewed Mar 18, 2026

View reviewed changes

thesimplekid added this to the 0.16.0 milestone Mar 19, 2026

	mintUrl: "https://testnut.cashu.space",
	mintUrl: "https://testnut.cashudevkit.org",

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crodas commented Mar 6, 2026 • edited by thesimplekid Loading Uh oh! There was an error while loading. Please reload this page.

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Description

Notes to the reviewers

Suggested CHANGELOG Updates

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Checklist

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thesimplekid commented Mar 11, 2026

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crodas commented Mar 6, 2026 •

edited by thesimplekid

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