Switch PluginFrontend to domain sockets on macOS

Author: bell-db

bridge/src/main/scala/protocbridge/frontend/MacPluginFrontend.scala

@@ -1,8 +1,14 @@
 package protocbridge.frontend
 
+import org.newsclub.net.unix.AFUNIXServerSocket
+import protocbridge.{ExtraEnv, ProtocCodeGenerator}
+
+import java.net.ServerSocket
 import java.nio.file.attribute.PosixFilePermission
 import java.nio.file.{Files, Path}
 import java.{util => ju}
+import scala.concurrent.ExecutionContext.Implicits.global
+import scala.concurrent.{Future, blocking}
 
 /** PluginFrontend for macOS.
   *
@@ -12,16 +18,58 @@ import java.{util => ju}
   * widely available on macOS, this is the simplest and most reliable solution
   * for macOS.
   */
-object MacPluginFrontend extends SocketBasedPluginFrontend {
+object MacPluginFrontend extends PluginFrontend {
+  case class InternalState(
+      tempDirPath: Path,
+      socketPath: Path,
+      serverSocket: ServerSocket,
+      shellScript: Path
+  )
+
+  override def prepare(
+      plugin: ProtocCodeGenerator,
+      env: ExtraEnv
+  ): (Path, InternalState) = {
+    val tempDirPath = Files.createTempDirectory("protopipe-")
+    val socketPath = tempDirPath.resolve("socket")
+    val serverSocket = AFUNIXServerSocket.bindOn(socketPath, true)
+    val sh = createShellScript(socketPath)
+
+    Future {
+      blocking {
+        // Accept a single client connection from the shell script.
+        val client = serverSocket.accept()
+        try {
+          val response =
+            PluginFrontend.runWithInputStream(
+              plugin,
+              client.getInputStream,
+              env
+            )
+          client.getOutputStream.write(response)
+        } finally {
+          client.close()
+        }
+      }
+    }
+    (sh, InternalState(tempDirPath, socketPath, serverSocket, sh))
+  }
+
+  override def cleanup(state: InternalState): Unit = {
+    state.serverSocket.close()
+    if (sys.props.get("protocbridge.debug") != Some("1")) {
+      Files.delete(state.tempDirPath)
+      Files.delete(state.shellScript)
+    }
+  }
 
-  protected def createShellScript(port: Int): Path = {
+  private def createShellScript(socketPath: Path): Path = {
     val shell = sys.env.getOrElse("PROTOCBRIDGE_SHELL", "/bin/sh")
-    // We use 127.0.0.1 instead of localhost for the (very unlikely) case that localhost is missing from /etc/hosts.
     val scriptName = PluginFrontend.createTempFile(
       "",
       s"""|#!$shell
           |set -e
-          |nc 127.0.0.1 $port
+          |nc -U "$socketPath"
       """.stripMargin
     )
     val perms = new ju.HashSet[PosixFilePermission]

build.sbt

@@ -29,7 +29,8 @@ lazy val bridge: Project = project
       "org.scalatest" %% "scalatest" % "3.2.17" % "test",
       "org.scalacheck" %% "scalacheck" % "1.17.0" % "test",
       "org.scala-lang.modules" %% "scala-collection-compat" % "2.11.0" % "test",
-      "io.get-coursier" %% "coursier" % coursierVersion % "test"
+      "io.get-coursier" %% "coursier" % coursierVersion % "test",
+      "com.kohlschutter.junixsocket" % "junixsocket-core" % "2.10.0"
     ),
     scalacOptions ++= (if (scalaVersion.value.startsWith("2.13."))
                          Seq("-Wconf:origin=.*JavaConverters.*:s")