support for non-sendable responses (#6)

* support for non-sendable responses

* adjusted github CI

Author: sliemeobn

.github/workflows/api-breakage.yml

@@ -0,0 +1,22 @@
+name: API breaking changes
+
+on:
+  pull_request:
+
+jobs:
+  linux:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    container:
+      image: swift:latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+    # https://github.com/actions/checkout/issues/766
+    - name: Mark the workspace as safe
+      run: git config --global --add safe.directory ${GITHUB_WORKSPACE}
+    - name: API breaking changes
+      run: |
+        swift package diagnose-api-breaking-changes origin/${GITHUB_BASE_REF}

.github/workflows/ci.yaml

@@ -16,7 +16,7 @@ jobs:
     timeout-minutes: 15
     strategy:
       matrix:
-        image: ["swift:5.10", "swiftlang/swift:nightly-6.0-jammy"]
+        image: ["swift:5.10", "swift:6.0"]
 
     container:
       image: ${{ matrix.image }}

.gitignore

@@ -6,4 +6,5 @@ DerivedData/
 .swiftpm/configuration/registries.json
 .swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata
 .netrc
-Package.resolved
+Package.resolved
+.vscode/

Package.swift

@@ -23,7 +23,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/vapor/vapor.git", from: "4.102.0"),
-        .package(url: "https://github.com/sliemeobn/elementary.git", .upToNextMajor(from: "0.3.0")),
+        .package(url: "https://github.com/sliemeobn/elementary.git", from: "0.4.3"),
     ],
     targets: [
         .target(

Sources/VaporElementary/HTMLResponse.swift

@@ -14,11 +14,14 @@ import Vapor
 ///     }
 ///   }
 /// }
+///
+/// NOTE: For non-sendable HTML values, the resulting response body can only be written once.
+/// Multiple writes will result in a runtime error.
 /// ```
 public struct HTMLResponse: Sendable {
     // NOTE: The Sendable requirement on Content can probably be removed in Swift 6 using a sending parameter, and some fancy ~Copyable @unchecked Sendable box type.
     // We only need to pass the HTML value to the response generator body closure
-    private let content: any HTML & Sendable
+    private let value: _SendableAnyHTMLBox
 
     /// The number of bytes to write to the response body at a time.
     ///
@@ -45,13 +48,30 @@ public struct HTMLResponse: Sendable {
     ///   - additionalHeaders: Additional headers to be merged with predefined headers.
     ///   - content: The `HTML` content to render in the response.
     public init(chunkSize: Int = 1024, additionalHeaders: HTTPHeaders = [:], @HTMLBuilder content: () -> some HTML & Sendable) {
+        self.init(chunkSize: chunkSize, additionalHeaders: additionalHeaders, value: .init(content()))
+    }
+
+    #if compiler(>=6.0)
+    @available(macOS 15, *)
+    /// Creates a new HTMLResponse
+    ///
+    /// - Parameters:
+    ///   - chunkSize: The number of bytes to write to the response body at a time.
+    ///   - additionalHeaders: Additional headers to be merged with predefined headers.
+    ///   - content: The `HTML` content to render in the response.
+    public init(chunkSize: Int = 1024, additionalHeaders: HTTPHeaders = [:], @HTMLBuilder content: () -> sending some HTML) {
+        self.init(chunkSize: chunkSize, additionalHeaders: additionalHeaders, value: .init(content()))
+    }
+    #endif
+
+    init(chunkSize: Int, additionalHeaders: HTTPHeaders = [:], value: _SendableAnyHTMLBox) {
         self.chunkSize = chunkSize
         if additionalHeaders.contains(name: .contentType) {
             self.headers = additionalHeaders
         } else {
             self.headers.add(contentsOf: additionalHeaders)
         }
-        self.content = content()
+        self.value = value
     }
 }
 
@@ -60,8 +80,13 @@ extension HTMLResponse: AsyncResponseEncodable {
         Response(
             status: .ok,
             headers: self.headers,
-            body: .init(asyncStream: { [content, chunkSize] writer in
-                try await writer.writeHTML(content, chunkSize: chunkSize)
+            body: .init(asyncStream: { [value, chunkSize] writer in
+                guard let html = value.tryTake() else {
+                    assertionFailure("Non-sendable HTML value consumed more than once")
+                    request.logger.error("Non-sendable HTML value consumed more than once")
+                    throw Abort(.internalServerError)
+                }
+                try await writer.writeHTML(html, chunkSize: chunkSize)
                 try await writer.write(.end)
             })
         )

Sources/VaporElementary/HTMLResponseBodyWriter.swift

@@ -1,9 +1,9 @@
 import Elementary
 import Vapor
 
-struct HTMLResponseBodyStreamWriter: HTMLStreamWriter {
+struct HTMLResponseBodyStreamWriter<Writer: AsyncBodyStreamWriter>: HTMLStreamWriter {
     let allocator: ByteBufferAllocator = .init()
-    var writer: any AsyncBodyStreamWriter
+    var writer: Writer
 
     mutating func write(_ bytes: ArraySlice<UInt8>) async throws {
         try await self.writer.writeBuffer(self.allocator.buffer(bytes: bytes))

Tests/VaporElementaryTests/NonSendableHTMLResponseTests.swift

@@ -0,0 +1,51 @@
+import Elementary
+import Vapor
+import VaporElementary
+import XCTest
+import XCTVapor
+
+final class NonSendableHTMLResponseTests: XCTestCase {
+    var app: Application!
+
+    override func setUp() async throws {
+        self.app = try await Application.make(.testing)
+    }
+
+    override func tearDown() async throws {
+        try await self.app.asyncShutdown()
+    }
+
+    func testAllowsSendableValuesToBeWrittenTwice() async throws {
+        self.app.get { req in
+            let html = HTMLResponse { "Hello" }
+            _ = try await html.encodeResponse(for: req).body.collect(on: req.eventLoop)
+            return html
+        }
+
+        let response = try await app.sendRequest(.GET, "/")
+        XCTAssertEqual(response.status, .ok)
+        XCTAssertEqual(String(buffer: response.body), #"Hello"#)
+    }
+
+    #if compiler(>=6.0)
+    func testRespondsWithANonSendable() async throws {
+        guard #available(macOS 15.0, *) else {
+            throw XCTSkip("Test requires macOS 15.0")
+        }
+        self.app.get { _ in HTMLResponse { div { NonSendableHTML() } } }
+
+        let response = try await app.sendRequest(.GET, "/")
+        XCTAssertEqual(response.status, .ok)
+        XCTAssertEqual(String(buffer: response.body), #"<div>Hello</div>"#)
+    }
+    #endif
+}
+
+@available(*, unavailable)
+extension NonSendableHTML: Sendable {}
+
+struct NonSendableHTML: HTML {
+    var content: some HTML {
+        "Hello"
+    }
+}