Mark types Sendable (#83)

Author: ktoso

Sources/Instrumentation/Instrument.swift

@@ -14,8 +14,15 @@
 
 import InstrumentationBaggage
 
+/// Typealias used to simplify Support of old Swift versions which do not have `Sendable` defined.
+#if swift(>=5.6.0)
+@preconcurrency public protocol _SwiftInstrumentationSendable: Sendable {}
+#else
+public protocol _SwiftInstrumentationSendable {}
+#endif
+
 /// Conforming types are used to extract values from a specific `Carrier`.
-public protocol Extractor {
+public protocol Extractor: _SwiftInstrumentationSendable {
     /// The carrier to extract values from.
     associatedtype Carrier
 
@@ -28,7 +35,7 @@ public protocol Extractor {
 }
 
 /// Conforming types are used to inject values into a specific `Carrier`.
-public protocol Injector {
+public protocol Injector: _SwiftInstrumentationSendable {
     /// The carrier to inject values into.
     associatedtype Carrier
 
@@ -43,7 +50,7 @@ public protocol Injector {
 
 /// Conforming types are usually cross-cutting tools like tracers. They are agnostic of what specific `Carrier` is used
 /// to propagate metadata across boundaries, but instead just specify what values to use for which keys.
-public protocol Instrument {
+public protocol Instrument: _SwiftInstrumentationSendable {
     /// Extract values from a `Carrier` by using the given extractor and inject them into the given `Baggage`.
     /// It's quite common for `Instrument`s to come up with new values if they weren't passed along in the given `Carrier`.
     ///

Sources/Tracing/Span.swift

@@ -12,7 +12,11 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Dispatch
+#if swift(>=5.6.0)
+@preconcurrency import struct Dispatch.DispatchWallTime
+#else
+import struct Dispatch.DispatchWallTime
+#endif
 @_exported import InstrumentationBaggage
 
 /// A `Span` represents an interval from the start of an operation to its end, along with additional metadata included
@@ -22,7 +26,7 @@ import Dispatch
 /// Creating a `Span` is delegated to a ``Tracer`` and end users should never create them directly.
 ///
 /// - SeeAlso: For more details refer to the [OpenTelemetry Specification: Span](https://github.com/open-telemetry/opentelemetry-specification/blob/v0.7.0/specification/trace/api.md#span) which this type is compatible with.
-public protocol Span: AnyObject {
+public protocol Span: AnyObject, _SwiftTracingSendableSpan {
     /// The read-only `Baggage` of this `Span`, set when starting this `Span`.
     var baggage: Baggage { get }
 
@@ -233,8 +237,13 @@ public enum SpanAttribute: Equatable {
     case string(String)
     case stringArray([String])
 
+    #if swift(>=5.6)
+    case stringConvertible(CustomStringConvertible & Sendable)
+    case stringConvertibleArray([CustomStringConvertible & Sendable])
+    #else
     case stringConvertible(CustomStringConvertible)
     case stringConvertibleArray([CustomStringConvertible])
+    #endif
 
     #if swift(>=5.2)
     // older swifts get confused and can't resolve if we mean the `case int(Int64)` or any of those overloads
@@ -383,11 +392,18 @@ extension Array: SpanAttributeConvertible where Element: SpanAttributeConvertibl
             return .boolArray(value)
         } else if let value = self as? [String] {
             return .stringArray(value)
-        } else if let value = self as? [CustomStringConvertible] {
+        }
+        #if swift(>=5.6.0)
+        if let value = self as? [CustomStringConvertible & Sendable] {
+            return .stringConvertibleArray(value)
+        }
+        #else
+        if let value = self as? [CustomStringConvertible] {
             return .stringConvertibleArray(value)
-        } else {
-            fatalError("Not supported SpanAttribute array type: \(type(of: self))")
         }
+        #endif
+
+        fatalError("Not supported SpanAttribute array type: \(type(of: self))")
     }
 }
 
@@ -650,10 +666,26 @@ public struct SpanLink {
 
     /// Create a new `SpanLink`.
     /// - Parameters:
-    ///   - context: The `Baggage` identifying the targeted ``Span``.
+    ///   - baggage: The `Baggage` identifying the targeted ``Span``.
     ///   - attributes: ``SpanAttributes`` that further describe the link. Defaults to no attributes.
     public init(baggage: Baggage, attributes: SpanAttributes = [:]) {
         self.baggage = baggage
         self.attributes = attributes
     }
 }
+
+#if compiler(>=5.6)
+@preconcurrency public protocol _SwiftTracingSendableSpan: Sendable {}
+#else
+public protocol _SwiftTracingSendableSpan {}
+#endif
+
+#if compiler(>=5.6)
+extension SpanAttributes: Sendable {}
+extension SpanAttribute: Sendable {} // @unchecked because some payloads are CustomStringConvertible
+extension SpanStatus: Sendable {}
+extension SpanEvent: Sendable {}
+extension SpanKind: Sendable {}
+extension SpanStatus.Code: Sendable {}
+extension SpanLink: Sendable {}
+#endif

Sources/Tracing/Tracer.swift

@@ -29,7 +29,7 @@ public protocol Tracer: Instrument {
     ///   - operationName: The name of the operation being traced. This may be a handler function, database call, ...
     ///   - baggage: The `Baggage` providing information on where to start the new ``Span``.
     ///   - kind: The ``SpanKind`` of the new ``Span``.
-    ///   - time: The `DispatchTime` at which to start the new ``Span``.
+    ///   - time: The time at which to start the new ``Span``.
     ///   - function: The function name in which the span was started
     ///   - fileID: The `fileID` where the span was started.
     ///   - line: The file line where the span was started.

Tests/TracingTests/DynamicTracepointTracerTests.swift

@@ -104,6 +104,7 @@ final class DynamicTracepointTracerTests: XCTestCase {
     }
 }
 
+/// Only intended to be used in single-threaded testing.
 final class DynamicTracepointTestTracer: Tracer {
     private(set) var activeTracepoints: Set<TracepointID> = []
 
@@ -227,6 +228,7 @@ final class DynamicTracepointTestTracer: Tracer {
 }
 
 extension DynamicTracepointTestTracer {
+    /// Only intended to be used in single-threaded testing.
     final class TracepointSpan: Tracing.Span {
         private let operationName: String
         private let kind: SpanKind
@@ -288,3 +290,8 @@ extension DynamicTracepointTestTracer {
         }
     }
 }
+
+#if compiler(>=5.6.0)
+extension DynamicTracepointTestTracer: @unchecked Sendable {} // only intended for single threaded testing
+extension DynamicTracepointTestTracer.TracepointSpan: @unchecked Sendable {} // only intended for single threaded testing
+#endif

Tests/TracingTests/SpanTests.swift

@@ -244,7 +244,7 @@ public struct HTTPAttributes: SpanAttributeNamespace {
     }
 }
 
-public struct CustomAttributeValue: Equatable, CustomStringConvertible, SpanAttributeConvertible {
+public struct CustomAttributeValue: Equatable, _CustomAttributeValueSendable, CustomStringConvertible, SpanAttributeConvertible {
     public func toSpanAttribute() -> SpanAttribute {
         .stringConvertible(self)
     }
@@ -255,6 +255,12 @@ public struct CustomAttributeValue: Equatable, CustomStringConvertible, SpanAttr
 }
 #endif
 
+#if swift(>=5.6.0)
+typealias _CustomAttributeValueSendable = Sendable
+#else
+typealias _CustomAttributeValueSendable = Any
+#endif
+
 private struct TestBaggageContextKey: BaggageKey {
     typealias Value = String
 }

Tests/TracingTests/TestTracer.swift

@@ -18,6 +18,7 @@ import Instrumentation
 import InstrumentationBaggage
 import Tracing
 
+/// Only intended to be used in single-threaded testing.
 final class TestTracer: Tracer {
     private(set) var spans = [TestSpan]()
     var onEndSpan: (Span) -> Void = { _ in }
@@ -93,6 +94,7 @@ extension Baggage {
     }
 }
 
+/// Only intended to be used in single-threaded testing.
 final class TestSpan: Span {
     private let operationName: String
     private let kind: SpanKind
@@ -156,3 +158,8 @@ final class TestSpan: Span {
         self.onEnd(self)
     }
 }
+
+#if compiler(>=5.6.0)
+extension TestTracer: @unchecked Sendable {} // only intended for single threaded testing
+extension TestSpan: @unchecked Sendable {} // only intended for single threaded testing
+#endif

Tests/TracingTests/TracedLockTests.swift

@@ -58,6 +58,7 @@ enum TaskIDKey: BaggageKey {
 // ==== ------------------------------------------------------------------------
 // MARK: PrintLn Tracer
 
+/// Only intended to be used in single-threaded testing.
 private final class TracedLockPrintlnTracer: Tracer {
     func startSpan(
         _ operationName: String,
@@ -158,3 +159,8 @@ private final class TracedLockPrintlnTracer: Tracer {
         }
     }
 }
+
+#if compiler(>=5.6.0)
+extension TracedLockPrintlnTracer: Sendable {}
+extension TracedLockPrintlnTracer.TracedLockPrintlnSpan: @unchecked Sendable {} // only intended for single threaded testing
+#endif