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Add trailer support to URLSession backend #122

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Add trailer support to URLSession backend #122

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d531316
Add trailer support to URLSession backend
guoye-zhang Feb 27, 2026
a758667
Set on the input stream instead
guoye-zhang Mar 7, 2026
a15a232
Merge main into urlsession-trailer
guoye-zhang Mar 7, 2026
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13 changes: 12 additions & 1 deletion Sources/HTTPClient/URLSession/URLSessionRequestStreamBridge.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -105,8 +105,19 @@ final class URLSessionRequestStreamBridge: NSObject, StreamDelegate, Sendable {
}
}

func close() {
func close(trailerFields: HTTPFields?) {
self.lockedState.withLock { state in
if let trailerFields {
var trailerNames: Set<HTTPField.Name> = []
for field in trailerFields {
trailerNames.insert(field.name)
}
var trailerDictionary: [String: String] = [:]
for name in trailerNames {
trailerDictionary[name.rawName] = trailerFields[name]
}
state.inputStream.setProperty(trailerDictionary, forKey: .init("_kCFStreamPropertyHTTPTrailer"))
}
state.outputStream.close()
}
}
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2 changes: 1 addition & 1 deletion Sources/HTTPClient/URLSession/URLSessionTaskDelegateBridge+ConcludingAsyncReader.swift
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Expand Up @@ -21,7 +21,7 @@ extension URLSessionTaskDelegateBridge: ConcludingAsyncReader {
func consumeAndConclude<Return, Failure: Error>(
body: (consuming sending URLSessionTaskDelegateBridge) async throws(Failure) -> Return
) async throws(Failure) -> (Return, HTTPFields?) {
try await (body(self), nil)
try await (body(self), self.responseTrailerFields)
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@guoye-zhang guoye-zhang Feb 28, 2026

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One of the reasons I think early returning before completing the read should throw is that we don't know whether nil means a trailer isn't present or it hasn't been received.

}
}

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24 changes: 20 additions & 4 deletions Sources/HTTPClient/URLSession/URLSessionTaskDelegateBridge.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -74,10 +74,15 @@ final class URLSessionTaskDelegateBridge: NSObject, Sendable, URLSessionDataDele
}
var state: State = .awaitingResponse
var completionContinuation: CheckedContinuation<Void, Never>? = nil
var responseTrailerFields: HTTPFields?
}

private let state: Mutex<TaskState> = .init(.init())

var responseTrailerFields: HTTPFields? {
self.state.withLock { $0.responseTrailerFields }
}

func urlSession(
_ session: URLSession,
dataTask: URLSessionDataTask,
Expand Down Expand Up @@ -153,6 +158,15 @@ final class URLSessionTaskDelegateBridge: NSObject, Sendable, URLSessionDataDele
state.state = .awaitingConsumption(existingData, complete: true, error: error, suspendedTask: nil)
}
state.completionContinuation = nil
if let trailerDictionary = task.value(forKey: "_trailers") as? [String: String] {
var trailerFields = HTTPFields()
for (name, value) in trailerDictionary {
if let name = HTTPField.Name(name) {
trailerFields.append(.init(name: name, value: value))
}
}
state.responseTrailerFields = trailerFields
}
}
return state
}
Expand Down Expand Up @@ -247,15 +261,16 @@ final class URLSessionTaskDelegateBridge: NSObject, Sendable, URLSessionDataDele
let bridge = URLSessionRequestStreamBridge(task: task)
completionHandler(bridge.inputStream)
do {
_ = try await requestBody.produce(into: bridge)
let trailerFields = try await requestBody.produce(into: bridge)
bridge.close(trailerFields: trailerFields)
} catch {
if bridge.writeFailed {
// Ignore error
} else {
self.requestBodyStreamFailed(with: error)
}
bridge.close(trailerFields: nil)
}
bridge.close()
}
}
}
Expand All @@ -277,15 +292,16 @@ final class URLSessionTaskDelegateBridge: NSObject, Sendable, URLSessionDataDele
let bridge = URLSessionRequestStreamBridge(task: task)
completionHandler(bridge.inputStream)
do {
_ = try await requestBody.produce(offset: offset, into: bridge)
let trailerFields = try await requestBody.produce(offset: offset, into: bridge)
bridge.close(trailerFields: trailerFields)
} catch {
if bridge.writeFailed {
// Ignore error
} else {
self.requestBodyStreamFailed(with: error)
}
bridge.close(trailerFields: nil)
}
bridge.close()
}
}
}
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