Fix some more Swift concurrency issues

Converted some more vars to lets. Swift still complains about async calls. I believe the next step would be to make all UniFFI objects conform to `Sendable`. See mozilla#2279.
bendk · Oct 31, 2024 · a3032a3 · a3032a3
1 parent 1c8dd50
commit a3032a3
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Showing 6 changed files with 12 additions and 6 deletions.
diff --git a/uniffi_bindgen/src/bindings/swift/templates/Async.swift b/uniffi_bindgen/src/bindings/swift/templates/Async.swift
@@ -84,7 +84,7 @@ private func uniffiTraitInterfaceCallAsyncWithError<T, E>(
 
 // Borrow the callback handle map implementation to store foreign future handles
 // TODO: consolidate the handle-map code (https://github.com/mozilla/uniffi-rs/pull/1823)
-fileprivate var UNIFFI_FOREIGN_FUTURE_HANDLE_MAP = UniffiHandleMap<UniffiForeignFutureTask>()
+fileprivate let UNIFFI_FOREIGN_FUTURE_HANDLE_MAP = UniffiHandleMap<UniffiForeignFutureTask>()
 
 // Protocol for tasks that handle foreign futures.
 //

diff --git a/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceImpl.swift b/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceImpl.swift
@@ -6,7 +6,10 @@ fileprivate struct {{ trait_impl }} {
 
     // Create the VTable using a series of closures.
     // Swift automatically converts these into C callback functions.
-    static var vtable: {{ vtable|ffi_type_name }} = {{ vtable|ffi_type_name }}(
+    //
+    // This is a var, since we pass a pointer to the Rust code, but it's not actually mutated in
+    // practice
+    static nonisolated(unsafe) var vtable: {{ vtable|ffi_type_name }} = {{ vtable|ffi_type_name }}(
         {%- for (ffi_callback, meth) in vtable_methods %}
         {{ meth.name()|fn_name }}: { (
             {%- for arg in ffi_callback.arguments() %}

diff --git a/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceTemplate.swift b/uniffi_bindgen/src/bindings/swift/templates/CallbackInterfaceTemplate.swift
@@ -16,7 +16,7 @@
 @_documentation(visibility: private)
 #endif
 fileprivate struct {{ ffi_converter_name }} {
-    fileprivate static var handleMap = UniffiHandleMap<{{ type_name }}>()
+    fileprivate static let handleMap = UniffiHandleMap<{{ type_name }}>()
 }
 
 #if swift(>=5.8)

diff --git a/uniffi_bindgen/src/bindings/swift/templates/HandleMap.swift b/uniffi_bindgen/src/bindings/swift/templates/HandleMap.swift
@@ -1,6 +1,7 @@
-fileprivate class UniffiHandleMap<T> {
-    private var map: [UInt64: T] = [:]
+fileprivate final class UniffiHandleMap<T>: @unchecked Sendable {
+    // All mutation happens with this lock held, which is why we implement @unchecked Sendable.
     private let lock = NSLock()
+    private var map: [UInt64: T] = [:]
     private var currentHandle: UInt64 = 1
 
     func insert(obj: T) -> UInt64 {

diff --git a/uniffi_bindgen/src/bindings/swift/templates/ObjectTemplate.swift b/uniffi_bindgen/src/bindings/swift/templates/ObjectTemplate.swift
@@ -132,7 +132,7 @@ open class {{ impl_class_name }}:
 #endif
 public struct {{ ffi_converter_name }}: FfiConverter {
     {%- if obj.has_callback_interface() %}
-    fileprivate static var handleMap = UniffiHandleMap<{{ type_name }}>()
+    fileprivate static let handleMap = UniffiHandleMap<{{ type_name }}>()
     {%- endif %}
 
     typealias FfiType = UnsafeMutableRawPointer

diff --git a/uniffi_bindgen/src/bindings/swift/test.rs b/uniffi_bindgen/src/bindings/swift/test.rs
@@ -96,6 +96,8 @@ fn compile_swift_module<T: AsRef<OsStr>>(
     command
         .current_dir(out_dir)
         .arg("-emit-module")
+        // TODO(2279): Fix concurrency issues and uncomment this
+        //.arg("-strict-concurrency=complete")
         .arg("-module-name")
         .arg(module_name)
         .arg("-o")