Add user script data channel

Sources/LanguageClient/DataChannel+UserScript.swift

@@ -0,0 +1,95 @@
+import Foundation
+import LanguageServerProtocol
+import JSONRPC
+
+
+#if canImport(ProcessEnv)
+import ProcessEnv
+
+#if compiler(>=5.9)
+
+/// The user script directory for this app.
+///
+@available(macOS 12.0, *)
+private let userScriptDirectory = try? FileManager.default.url(for: .applicationScriptsDirectory,
+																															 in: .userDomainMask,
+																															 appropriateFor: nil,
+																															 create: false)
+
+extension DataChannel {
+
+	/// Create a `DataChannel` that connects to an application user script in the application scripts directory.
+	///
+	/// - Parameters:
+	///   - scriptPath: The path of the application user script.
+	///   - arguments: The script arguments.
+	///   - terminationHandler: Termination handler to invoke when the user script terminates.
+	///
+	@available(macOS 12.0, *)
+	public static func userScriptChannel(scriptPath: String,
+																			 arguments: [String] = [],
+																			 terminationHandler: @escaping @Sendable () -> Void)
+	throws -> DataChannel
+	{
+		guard let scriptURL = userScriptDirectory?.appendingPathComponent(scriptPath) else {
+			throw CocoaError(.fileNoSuchFile)
+		}
+
+		// Allocate pipes for the standard handles
+		let stdinPipe = Pipe()
+		let stdoutPipe = Pipe()
+		let stderrPipe = Pipe()
+
+		let (stream, continuation) = DataSequence.makeStream()
+
+		// Forward stdout to the data channel
+		Task {
+			let dataStream = stdoutPipe.fileHandleForReading.dataStream
+			let byteStream = AsyncByteSequence(base: dataStream)
+			let framedData = AsyncMessageFramingSequence(base: byteStream)
+
+			for try await data in framedData {
+				continuation.yield(data)
+			}
+
+			continuation.finish()
+		}
+
+		// Log stderr
+		Task {
+			for try await line in stderrPipe.fileHandleForReading.bytes.lines {
+				print("stderr: ", line)
+			}
+		}
+
+		// Launch the script asynchronously
+		Task {
+
+			// NB: Needs to happen in the task as `NSUserUnixTask` is not sendable.
+			let unixTask = try NSUserUnixTask(url: scriptURL)
+
+			unixTask.standardInput  = stdinPipe.fileHandleForReading
+			unixTask.standardOutput = stdoutPipe.fileHandleForWriting
+			unixTask.standardError  = stderrPipe.fileHandleForWriting
+
+			defer {
+				continuation.finish()
+				terminationHandler()
+			}
+			try await unixTask.execute(withArguments: arguments)
+		}
+
+		// Forward messages from the data channel into stdin
+		let handler: DataChannel.WriteHandler = {
+			let data = MessageFraming.frame($0)
+
+			try stdinPipe.fileHandleForWriting.write(contentsOf: data)
+		}
+
+		return DataChannel(writeHandler: handler, dataSequence: stream)
+	}
+}
+
+#endif
+
+#endif