fix(uniffi): register the Bytes custom type once, in livekit-common

.changeset/reuse_datatrack_bytes_converter.md

@@ -0,0 +1,7 @@
+---
+livekit-uniffi: patch
+livekit-datatrack: patch
+livekit-common: patch
+---
+
+Register the `Bytes` UniFFI custom type once in `livekit-common` and borrow it from each component with `uniffi::use_remote_type!`, so the converter is emitted once and the post-generation Swift workaround is no longer needed

.github/workflows/uniffi-swift.yml

@@ -85,7 +85,7 @@ jobs:
 
       - name: Publish to hosting repo
         if: ${{ !inputs.dry_run }}
-        uses: livekit/publish-xcframework-action@200ee4984ef1b68068c0b3c4e87e798988730c90 # main @ fix: abort on missing source files (#3)
+        uses: livekit/publish-xcframework-action@a1bc3de909f9c0a2b7f92172a95d6dd35cb20b1a # main @ feat: allow path patterns as file sources (#5)
         with:
           xcframework-zip: ${{ env.OUTPUT_DIR }}/Rust${{ env.SPM_NAME }}.xcframework.zip
           version: ${{ inputs.version }}
@@ -96,8 +96,9 @@ jobs:
             ${{ env.OUTPUT_DIR }}/${{ env.SPM_NAME }}.podspec:${{ env.SPM_NAME }}.podspec
             ${{ env.OUTPUT_DIR }}/LICENSE:LICENSE
             ${{ env.OUTPUT_DIR }}/PrivacyInfo.xcprivacy:PrivacyInfo.xcprivacy
-            ${{ env.OUTPUT_DIR }}/Sources/${{ env.SPM_NAME }}/livekit_uniffi.swift:Sources/${{ env.SPM_NAME }}/livekit_uniffi.swift
-            ${{ env.OUTPUT_DIR }}/Sources/${{ env.SPM_NAME }}/livekit_datatrack.swift:Sources/${{ env.SPM_NAME }}/livekit_datatrack.swift
+            # UniFFI emits one source per component, so match rather than list them:
+            # adding a component must not require a workflow change.
+            ${{ env.OUTPUT_DIR }}/Sources/${{ env.SPM_NAME }}/*.swift:Sources/${{ env.SPM_NAME }}/
           token: ${{ secrets.UNIFFI_XCFRAMEWORK_PAT }}
           pr-body: |
             Source tag: `${{ inputs.tag_name }}`

livekit-common/Cargo.toml

@@ -9,3 +9,10 @@ repository.workspace = true
 
 [dependencies]
 livekit-protocol = { workspace = true }
+bytes = { workspace = true, optional = true }
+uniffi = { workspace = true, features = ["scaffolding-ffi-buffer-fns"], optional = true }
+
+[features]
+# Exposes this crate's shared FFI type registrations. Enabled transitively by
+# livekit-uniffi so every component borrows one converter per type.
+uniffi = ["dep:uniffi", "dep:bytes"]

livekit-common/src/ffi_types.rs

@@ -0,0 +1,29 @@
+// Copyright 2026 LiveKit, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Shared UniFFI type registrations.
+//!
+//! A remote type such as [`bytes::Bytes`] can only be registered once per UniFFI component:
+//! `custom_type!` emits a `public` converter per component, and the generated Swift files are
+//! compiled into a single module, so a second registration fails to build. Registering it here
+//! and having each component borrow it with `uniffi::use_remote_type!` keeps exactly one
+//! declaration no matter how many crates need the type.
+//!
+//! Owning a registration requires being a UniFFI component: `custom_type!` needs
+//! `crate::UniFfiTag`, and bindgen rejects type metadata that belongs to no namespace
+//! (`Unknown namespace for CustomType`). Hence the `setup_scaffolding!` in `lib.rs`.
+
+use bytes::Bytes;
+
+uniffi::custom_type!(Bytes, Vec<u8>, { remote });

livekit-common/src/lib.rs

@@ -22,6 +22,14 @@ use livekit_protocol as proto;
 
 mod enum_dispatch;
 
+// Must sit at the crate root: it defines `crate::UniFfiTag`, which the registrations in
+// `ffi_types` resolve against.
+#[cfg(feature = "uniffi")]
+uniffi::setup_scaffolding!();
+
+#[cfg(feature = "uniffi")]
+mod ffi_types;
+
 // -------------------------------------------------------------------------------------------------
 // Client protocol
 // -------------------------------------------------------------------------------------------------

livekit-common/uniffi.toml

@@ -0,0 +1,4 @@
+[bindings.swift]
+# Matches the Rust<Name> convention used by the other components; the cargo-swift
+# fork folds every component's header into the single RustLiveKitUniFFI framework.
+ffi_module_name = "RustLiveKitCommon"

livekit-datatrack/Cargo.toml

@@ -9,6 +9,7 @@ repository.workspace = true
 
 [dependencies]
 livekit-protocol = { workspace = true }
+livekit-common = { workspace = true, optional = true }
 livekit-runtime = { workspace = true, features = ["tokio"] }
 log = { workspace = true }
 thiserror = { workspace = true }
@@ -25,7 +26,7 @@ uniffi = { workspace = true, features = ["scaffolding-ffi-buffer-fns"], optional
 indexmap = "2"
 
 [features]
-uniffi = ["dep:uniffi"]
+uniffi = ["dep:uniffi", "dep:livekit-common", "livekit-common/uniffi"]
 __fuzz = ["dep:fake"]
 
 [dev-dependencies]

livekit-datatrack/src/e2ee.rs

@@ -76,7 +76,7 @@ pub trait DecryptionProvider: Send + Sync + Debug {
 }
 
 #[cfg(feature = "uniffi")]
-uniffi::custom_type!(Bytes, Vec<u8>, { remote });
+uniffi::use_remote_type!(livekit_common::Bytes);
 
 #[cfg(feature = "uniffi")]
 uniffi::custom_type!(InitializationVector, Vec<u8>, {

livekit-uniffi/Cargo.toml

@@ -13,6 +13,7 @@ publish = false
 
 [dependencies]
 livekit-protocol = { workspace = true }
+livekit-common = { workspace = true, features = ["uniffi"] }
 livekit-api = { workspace = true, default-features = false, features = ["access-token"] }
 livekit-datatrack = { workspace = true, features = ["uniffi"] }
 uniffi = { workspace = true, features = ["scaffolding-ffi-buffer-fns", "tokio"] }

livekit-uniffi/Makefile.toml

@@ -475,24 +475,6 @@ mkdir -p "${out_dir}"
 mv "${SPM_NAME}" "${out_dir}"
 """
 
-# Post-generation Swift workarounds for issues cargo-swift / the templates don't handle.
-# Currently: the `Bytes` custom type is registered in both crates, so uniffi emits its
-# converter in both component Swift files, which collide in one module ("invalid
-# redeclaration of 'Bytes'"). Drop the duplicate from livekit_datatrack.swift.
-# Upstream: https://github.com/mozilla/uniffi-rs/issues/2933. Idempotent.
-[tasks.swift-workarounds]
-private = true
-script_runner = "@shell"
-script = '''
-file="${PACKAGES_DIR}/swift/${SPM_NAME}/Sources/${SPM_NAME}/livekit_datatrack.swift"
-if [ ! -f "$file" ]; then
-  echo "swift-workarounds: $file not found, skipping"
-  exit 0
-fi
-perl -0pi -e 's{public typealias Bytes = Data.*?public func FfiConverterTypeBytes_lower\(_ value: Bytes\) -> RustBuffer \{\n    return FfiConverterTypeBytes\.lower\(value\)\n\}}{// cargo-make swift-workarounds: duplicate Bytes converter removed (kept in livekit_uniffi.swift)}s' "$file"
-echo "swift-workarounds: ensured single Bytes converter in $file"
-'''
-
 [tasks.swift-package-flow]
 private = true
 dependencies = [
@@ -501,8 +483,7 @@ dependencies = [
     "swift-check-size",
     "swift-zip-xcframework",
     "swift-generate-manifest",
-    "swift-move-to-packages",
-    "swift-workarounds"
+    "swift-move-to-packages"
 ]
 
 [tasks.swift-package]

livekit-uniffi/src/common.rs

@@ -14,4 +14,8 @@
 
 use bytes::Bytes;
 
-uniffi::custom_type!(Bytes, Vec<u8>, { remote });
+// `Bytes` is registered once in livekit-common so every component that needs it borrows the
+// same converter; registering it here as well would emit a second `public typealias Bytes`
+// into this component's Swift file, and both files compile into one module.
+// Upstream: https://github.com/mozilla/uniffi-rs/issues/2933
+uniffi::use_remote_type!(livekit_common::Bytes);