HTTP: assert that user doesn't set CL & TE:chunked (#1556)

Motivation:

NIO users need to understand the semantic of the underlying protocol.
Therefore NIO does not (and in many case cannot) check all the
invariants. Generally however, we try to be helpful and assert a bunch
of things that a user has (hopefully) checked. That doesn't affect
performance and simplifies development for users.

Modifications:

- assert that request/response heads don't set content-length +
  transfer-encoding: chunked

Result:

Developers of libraries like AHC will have an easier time.

Sources/NIOCrashTester/CrashTestSuites.swift

@@ -16,4 +16,5 @@ let crashTestSuites: [String: Any] = [
     "EventLoopCrashTests": EventLoopCrashTests(),
     "ByteBufferCrashTests": ByteBufferCrashTests(),
     "SystemCrashTests": SystemCrashTests(),
+    "HTTPCrashTests": HTTPCrashTests(),
 ]

Sources/NIOCrashTester/CrashTests+HTTP.swift

@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2020 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import NIO
+import NIOHTTP1
+
+struct HTTPCrashTests {
+    let testEncodingChunkedAndContentLengthForRequestsCrashes = CrashTest(
+        regex: "^Assertion failed: illegal HTTP sent: HTTPRequestHead .* contains both a content-length and transfer-encoding:chunked",
+        {
+            let channel = EmbeddedChannel(handler: HTTPRequestEncoder())
+            _ = try? channel.writeAndFlush(
+                HTTPClientRequestPart.head(
+                    HTTPRequestHead(version: .init(major: 1, minor: 1),
+                                    method: .POST,
+                                    uri: "/",
+                                    headers: ["content-Length": "1",
+                                              "transfer-Encoding": "chunked"]))).wait()
+        })
+
+    let testEncodingChunkedAndContentLengthForResponseCrashes = CrashTest(
+        regex: "^Assertion failed: illegal HTTP sent: HTTPResponseHead .* contains both a content-length and transfer-encoding:chunked",
+        {
+            let channel = EmbeddedChannel(handler: HTTPResponseEncoder())
+            _ = try? channel.writeAndFlush(
+                HTTPServerResponsePart.head(
+                    HTTPResponseHead(version: .init(major: 1, minor: 1),
+                                     status: .ok,
+                                     headers: ["content-Length": "1",
+                                               "transfer-Encoding": "chunked"]))).wait()
+        })
+}

Sources/NIOCrashTester/OutputGrepper.swift

@@ -65,7 +65,9 @@ private final class GrepHandler: ChannelInboundHandler {
 
     func channelRead(context: ChannelHandlerContext, data: NIOAny) {
         let line = self.unwrapInboundIn(data)
-        if line.lowercased().starts(with: "fatal error: ") || line.lowercased().starts(with: "precondition failed: ") {
+        if line.lowercased().starts(with: "fatal error: ") ||
+            line.lowercased().starts(with: "precondition failed: ") ||
+            line.lowercased().starts(with: "assertion failed: ") {
             self.promise.succeed(line)
             context.close(promise: nil)
         }

Sources/NIOHTTP1/HTTPEncoder.swift

@@ -143,7 +143,11 @@ public final class HTTPRequestEncoder: ChannelOutboundHandler, RemovableChannelH
     public func write(context: ChannelHandlerContext, data: NIOAny, promise: EventLoopPromise<Void>?) {
         switch self.unwrapOutboundIn(data) {
         case .head(var request):
-            self.isChunked = sanitizeTransportHeaders(hasBody: request.method.hasRequestBody, headers: &request.headers, version: request.version) == .chunked
+            assert(!(request.headers.contains(name: "content-length") &&
+                        request.headers[canonicalForm: "transfer-encoding"].contains("chunked"[...])),
+                     "illegal HTTP sent: \(request) contains both a content-length and transfer-encoding:chunked")
+            self.isChunked = sanitizeTransportHeaders(hasBody: request.method.hasRequestBody,
+                                                      headers: &request.headers, version: request.version) == .chunked
 
             writeHead(wrapOutboundOut: self.wrapOutboundOut, writeStartLine: { buffer in
                 buffer.write(request: request)
@@ -177,8 +181,11 @@ public final class HTTPResponseEncoder: ChannelOutboundHandler, RemovableChannel
     public func write(context: ChannelHandlerContext, data: NIOAny, promise: EventLoopPromise<Void>?) {
         switch self.unwrapOutboundIn(data) {
         case .head(var response):
-
-            self.isChunked = sanitizeTransportHeaders(hasBody: response.status.mayHaveResponseBody ? .yes : .no, headers: &response.headers, version: response.version) == .chunked
+            assert(!(response.headers.contains(name: "content-length") &&
+                        response.headers[canonicalForm: "transfer-encoding"].contains("chunked"[...])),
+                     "illegal HTTP sent: \(response) contains both a content-length and transfer-encoding:chunked")
+            self.isChunked = sanitizeTransportHeaders(hasBody: response.status.mayHaveResponseBody ? .yes : .no,
+                                                      headers: &response.headers, version: response.version) == .chunked
 
             writeHead(wrapOutboundOut: self.wrapOutboundOut, writeStartLine: { buffer in
                 buffer.write(response: response)