[jsonrpc] Move close handler to start

Since the connection and message handler have a reciprocal need to know
about each other, move the closeHandler so that it has the opportunity
to call a method on the message handler if desired.

Sources/LanguageServerProtocolJSONRPC/JSONRPCConnection.swift

@@ -52,17 +52,15 @@ public final class JSONRPCConection {
   /// The set of currently outstanding outgoing requests along with information about how to decode and handle their responses.
   var outstandingRequests: [RequestID: OutstandingRequest] = [:]
 
-  var closeHandler: () -> Void
+  var closeHandler: (() -> Void)! = nil
 
   public init(
     protocol messageRegistry: MessageRegistry,
     inFD: Int32,
     outFD: Int32,
-    syncRequests: Bool = false,
-    closeHandler: @escaping () -> Void = {})
+    syncRequests: Bool = false)
   {
     state = .created
-    self.closeHandler = closeHandler
     self.messageRegistry = messageRegistry
     self.syncRequests = syncRequests
 
@@ -93,10 +91,11 @@ public final class JSONRPCConection {
   /// Start processing `inFD` and send messages to `receiveHandler`.
   ///
   /// - parameter receiveHandler: The message handler to invoke for requests received on the `inFD`.
-  public func start(receiveHandler: MessageHandler) {
+  public func start(receiveHandler: MessageHandler, closeHandler: @escaping () -> Void = {}) {
     precondition(state == .created)
     state = .running
     self.receiveHandler = receiveHandler
+    self.closeHandler = closeHandler
 
     receiveIO.read(offset: 0, length: Int.max, queue: queue) { done, data, errorCode in
       guard errorCode == 0 else {

Sources/sourcekit-lsp/main.swift

@@ -102,10 +102,7 @@ let clientConnection = JSONRPCConection(
   protocol: MessageRegistry.lspProtocol,
   inFD: STDIN_FILENO,
   outFD: STDOUT_FILENO,
-  syncRequests: options.syncRequests,
-  closeHandler: {
-  exit(0)
-})
+  syncRequests: options.syncRequests)
 
 let installPath = AbsolutePath(Bundle.main.bundlePath)
 ToolchainRegistry.shared = ToolchainRegistry(installPath: installPath, localFileSystem)
@@ -113,7 +110,9 @@ ToolchainRegistry.shared = ToolchainRegistry(installPath: installPath, localFile
 let server = SourceKitServer(client: clientConnection, options: options.serverOptions, onExit: {
   clientConnection.close()
 })
-clientConnection.start(receiveHandler: server)
+clientConnection.start(receiveHandler: server, closeHandler: {
+  exit(0)
+})
 
 Logger.shared.addLogHandler { message, _ in
   clientConnection.send(LogMessage(type: .log, message: message))

Tests/LanguageServerProtocolJSONRPCTests/ConnectionTests.swift

@@ -213,18 +213,17 @@ class ConnectionTests: XCTestCase {
       let conn = JSONRPCConection(
         protocol: MessageRegistry(requests: [], notifications: []),
         inFD: to.fileHandleForReading.fileDescriptor,
-        outFD: from.fileHandleForWriting.fileDescriptor,
-        closeHandler: {
-        // We get an error from XCTest if this is fulfilled more than once.
-        expectation.fulfill()
-      })
+        outFD: from.fileHandleForWriting.fileDescriptor)
 
       final class DummyHandler: MessageHandler {
         func handle<N: NotificationType>(_: N, from: ObjectIdentifier) {}
         func handle<R: RequestType>(_: R, id: RequestID, from: ObjectIdentifier, reply: @escaping (LSPResult<R.Response>) -> Void) {}
       }
 
-      conn.start(receiveHandler: DummyHandler())
+      conn.start(receiveHandler: DummyHandler(), closeHandler: {
+        // We get an error from XCTest if this is fulfilled more than once.
+        expectation.fulfill()
+      })
 
 
       close(to.fileHandleForWriting.fileDescriptor)