Don't join Set-Cookie headers together

Sources/NIOHTTP1/HTTPTypes.swift

@@ -149,6 +149,17 @@ public struct HTTPHeaders : Sequence, CustomStringConvertible {
 
     func write(buffer: inout ByteBuffer) {
         for (key, values) in storage {
+            if key != "set-cookie" {
+                writeListHeaderValues(buffer: &buffer, key: key, values: values)
+            } else {
+                writeSequentialHeaderValues(buffer: &buffer, key: key, values: values)
+            }
+        }
+        buffer.write(staticString: crlf)
+    }
+
+    /// Used for most HTTP headers, which can be represented as a single line joined by commas.
+    private func writeListHeaderValues(buffer: inout ByteBuffer, key: String, values: [(String, String)]) {
         buffer.write(string: key)
         buffer.write(staticString: headerSeparator)
 
@@ -162,8 +173,16 @@ public struct HTTPHeaders : Sequence, CustomStringConvertible {
         buffer.moveWriterIndex(to: writerIndex)
         buffer.write(staticString: crlf)
     }
+
+    /// Used for HTTP headers that cannot be joined with commas, e.g. set-cookie.
+    private func writeSequentialHeaderValues(buffer: inout ByteBuffer, key: String, values: [(String, String)]) {
+        for (_, value) in values {
+            buffer.write(string: key)
+            buffer.write(staticString: headerSeparator)
+            buffer.write(string: value)
             buffer.write(staticString: crlf)
         }
+    }
 
     public func makeIterator() -> AnyIterator<(name: String, value: String)> {
         return AnyIterator(HTTPHeadersIterator(wrapping: storage.makeIterator()))

Tests/NIOHTTP1Tests/HTTPHeadersTest+XCTest.swift

@@ -27,6 +27,7 @@ extension HTTPHeadersTest {
    static var allTests : [(String, (HTTPHeadersTest) -> () throws -> Void)] {
       return [
                 ("testCasePreservedButInsensitiveLookup", testCasePreservedButInsensitiveLookup),
+                ("testWriteHeadersSeparately", testWriteHeadersSeparately),
            ]
    }
 }

Tests/NIOHTTP1Tests/HTTPHeadersTest.swift

@@ -14,6 +14,7 @@
 
 import Foundation
 import XCTest
+@testable import NIO
 @testable import NIOHTTP1
 
 class HTTPHeadersTest : XCTestCase {
@@ -49,4 +50,25 @@ class HTTPHeadersTest : XCTestCase {
             }
         }
     }
+
+    func testWriteHeadersSeparately() {
+        let originalHeaders = [ ("User-Agent", "1"),
+                                ("host", "2"),
+                                ("X-SOMETHING", "3"),
+                                ("X-Something", "4"),
+                                ("SET-COOKIE", "foo=bar"),
+                                ("Set-Cookie", "buz=cux")]
+
+        let headers = HTTPHeaders(originalHeaders)
+        let channel = EmbeddedChannel()
+        var buffer = channel.allocator.buffer(capacity: 1024)
+        headers.write(buffer: &buffer)
+
+        let writtenBytes = buffer.string(at: buffer.readerIndex, length: buffer.readableBytes)!
+        XCTAssertTrue(writtenBytes.contains("user-agent: 1\r\n"))
+        XCTAssertTrue(writtenBytes.contains("host: 2\r\n"))
+        XCTAssertTrue(writtenBytes.contains("x-something: 3,4\r\n"))
+        XCTAssertTrue(writtenBytes.contains("set-cookie: foo=bar\r\n"))
+        XCTAssertTrue(writtenBytes.contains("set-cookie: buz=cux\r\n"))
+    }
 }