Switch PluginFrontend to sockets on macOS

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

@@ -0,0 +1,36 @@
+package protocbridge.frontend
+
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.{Files, Path}
+import java.{util => ju}
+
+/** PluginFrontend for macOS.
+  *
+  * Creates a server socket and uses `nc` to communicate with the socket. We use
+  * a server socket instead of named pipes because named pipes are unreliable on
+  * macOS: https://github.com/scalapb/protoc-bridge/issues/366. Since `nc` is
+  * widely available on macOS, this is the simplest and most reliable solution
+  * for macOS.
+  */
+object MacPluginFrontend extends SocketBasedPluginFrontend {
+
+  protected def createShellScript(port: Int): 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
+      """.stripMargin
+    )
+    val perms = new ju.HashSet[PosixFilePermission]
+    perms.add(PosixFilePermission.OWNER_EXECUTE)
+    perms.add(PosixFilePermission.OWNER_READ)
+    Files.setPosixFilePermissions(
+      scriptName,
+      perms
+    )
+    scriptName
+  }
+}

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

@@ -131,8 +131,13 @@ object PluginFrontend {
 
   def isWindows: Boolean = sys.props("os.name").startsWith("Windows")
 
+  def isMac: Boolean = sys.props("os.name").startsWith("Mac") || sys
+    .props("os.name")
+    .startsWith("Darwin")
+
   def newInstance: PluginFrontend = {
     if (isWindows) WindowsPluginFrontend
+    else if (isMac) MacPluginFrontend
     else PosixPluginFrontend
   }
 }

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

@@ -12,10 +12,13 @@ import scala.concurrent.ExecutionContext.Implicits.global
 import scala.sys.process._
 import java.{util => ju}
 
-/** PluginFrontend for Unix-like systems (Linux, Mac, etc)
+/** PluginFrontend for Unix-like systems <b>except macOS</b> (Linux, FreeBSD,
+  * etc)
   *
   * Creates a pair of named pipes for input/output and a shell script that
-  * communicates with them.
+  * communicates with them. Compared with `SocketBasedPluginFrontend`, this
+  * frontend doesn't rely on `nc` that might not be available in some
+  * distributions.
   */
 object PosixPluginFrontend extends PluginFrontend {
   case class InternalState(

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

@@ -0,0 +1,51 @@
+package protocbridge.frontend
+
+import protocbridge.{ExtraEnv, ProtocCodeGenerator}
+
+import java.net.ServerSocket
+import java.nio.file.{Files, Path}
+import scala.concurrent.ExecutionContext.Implicits.global
+import scala.concurrent.{Future, blocking}
+
+/** PluginFrontend for Windows and macOS where a server socket is used.
+  */
+abstract class SocketBasedPluginFrontend extends PluginFrontend {
+  case class InternalState(serverSocket: ServerSocket, shellScript: Path)
+
+  override def prepare(
+      plugin: ProtocCodeGenerator,
+      env: ExtraEnv
+  ): (Path, InternalState) = {
+    val ss = new ServerSocket(0) // Bind to any available port.
+    val sh = createShellScript(ss.getLocalPort)
+
+    Future {
+      blocking {
+        // Accept a single client connection from the shell script.
+        val client = ss.accept()
+        try {
+          val response =
+            PluginFrontend.runWithInputStream(
+              plugin,
+              client.getInputStream,
+              env
+            )
+          client.getOutputStream.write(response)
+        } finally {
+          client.close()
+        }
+      }
+    }
+
+    (sh, InternalState(ss, sh))
+  }
+
+  override def cleanup(state: InternalState): Unit = {
+    state.serverSocket.close()
+    if (sys.props.get("protocbridge.debug") != Some("1")) {
+      Files.delete(state.shellScript)
+    }
+  }
+
+  protected def createShellScript(port: Int): Path
+}

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

@@ -1,53 +1,15 @@
 package protocbridge.frontend
 
-import java.net.ServerSocket
-import java.nio.file.{Files, Path, Paths}
-
-import protocbridge.ExtraEnv
-import protocbridge.ProtocCodeGenerator
-
-import scala.concurrent.blocking
-
-import scala.concurrent.ExecutionContext.Implicits.global
-import scala.concurrent.Future
+import java.nio.file.{Path, Paths}
 
 /** A PluginFrontend that binds a server socket to a local interface. The plugin
   * is a batch script that invokes BridgeApp.main() method, in a new JVM with
   * the same parameters as the currently running JVM. The plugin will
   * communicate its stdin and stdout to this socket.
   */
-object WindowsPluginFrontend extends PluginFrontend {
-
-  case class InternalState(batFile: Path)
-
-  override def prepare(
-      plugin: ProtocCodeGenerator,
-      env: ExtraEnv
-  ): (Path, InternalState) = {
-    val ss = new ServerSocket(0)
-    val state = createWindowsScript(ss.getLocalPort)
-
-    Future {
-      blocking {
-        val client = ss.accept()
-        val response =
-          PluginFrontend.runWithInputStream(plugin, client.getInputStream, env)
-        client.getOutputStream.write(response)
-        client.close()
-        ss.close()
-      }
-    }
-
-    (state.batFile, state)
-  }
-
-  override def cleanup(state: InternalState): Unit = {
-    if (sys.props.get("protocbridge.debug") != Some("1")) {
-      Files.delete(state.batFile)
-    }
-  }
+object WindowsPluginFrontend extends SocketBasedPluginFrontend {
 
-  private def createWindowsScript(port: Int): InternalState = {
+  protected def createShellScript(port: Int): Path = {
     val classPath =
       Paths.get(getClass.getProtectionDomain.getCodeSource.getLocation.toURI)
     val classPathBatchString = classPath.toString.replace("%", "%%")
@@ -62,6 +24,6 @@ object WindowsPluginFrontend extends PluginFrontend {
         ].getName} $port
         """.stripMargin
     )
-    InternalState(batchFile)
+    batchFile
   }
 }

bridge/src/test/scala/protocbridge/frontend/MacPluginFrontendSpec.scala

@@ -0,0 +1,15 @@
+package protocbridge.frontend
+
+class MacPluginFrontendSpec extends OsSpecificFrontendSpec {
+  if (PluginFrontend.isMac) {
+    it must "execute a program that forwards input and output to given stream" in {
+      val state = testSuccess(MacPluginFrontend)
+      state.serverSocket.isClosed mustBe true
+    }
+
+    it must "not hang if there is an error in generator" in {
+      val state = testFailure(MacPluginFrontend)
+      state.serverSocket.isClosed mustBe true
+    }
+  }
+}

bridge/src/test/scala/protocbridge/frontend/OsSpecificFrontendSpec.scala

@@ -15,7 +15,7 @@ class OsSpecificFrontendSpec extends AnyFlatSpec with Matchers {
       generator: ProtocCodeGenerator,
       env: ExtraEnv,
       request: Array[Byte]
-  ): Array[Byte] = {
+  ): (frontend.InternalState, Array[Byte]) = {
     val (path, state) = frontend.prepare(
       generator,
       env
@@ -45,10 +45,12 @@ class OsSpecificFrontendSpec extends AnyFlatSpec with Matchers {
       )
     process.exitValue()
     frontend.cleanup(state)
-    actualOutput.toByteArray
+    (state, actualOutput.toByteArray)
   }
 
-  protected def testSuccess(frontend: PluginFrontend): Unit = {
+  protected def testSuccess(
+      frontend: PluginFrontend
+  ): frontend.InternalState = {
     val random = new Random()
     val toSend = Array.fill(123)(random.nextInt(256).toByte)
     val toReceive = Array.fill(456)(random.nextInt(256).toByte)
@@ -60,11 +62,15 @@ class OsSpecificFrontendSpec extends AnyFlatSpec with Matchers {
         toReceive
       }
     }
-    val response = testPluginFrontend(frontend, fakeGenerator, env, toSend)
+    val (state, response) =
+      testPluginFrontend(frontend, fakeGenerator, env, toSend)
     response mustBe toReceive
+    state
   }
 
-  protected def testFailure(frontend: PluginFrontend): Unit = {
+  protected def testFailure(
+      frontend: PluginFrontend
+  ): frontend.InternalState = {
     val random = new Random()
     val toSend = Array.fill(123)(random.nextInt(256).toByte)
     val env = new ExtraEnv(secondaryOutputDir = "tmp")
@@ -74,7 +80,9 @@ class OsSpecificFrontendSpec extends AnyFlatSpec with Matchers {
         throw new OutOfMemoryError("test error")
       }
     }
-    val response = testPluginFrontend(frontend, fakeGenerator, env, toSend)
+    val (state, response) =
+      testPluginFrontend(frontend, fakeGenerator, env, toSend)
     response.length must be > 0
+    state
   }
 }

bridge/src/test/scala/protocbridge/frontend/PosixPluginFrontendSpec.scala

@@ -1,7 +1,7 @@
 package protocbridge.frontend
 
 class PosixPluginFrontendSpec extends OsSpecificFrontendSpec {
-  if (!PluginFrontend.isWindows) {
+  if (!PluginFrontend.isWindows && !PluginFrontend.isMac) {
     it must "execute a program that forwards input and output to given stream" in {
       testSuccess(PosixPluginFrontend)
     }

bridge/src/test/scala/protocbridge/frontend/WindowsPluginFrontendSpec.scala

@@ -3,11 +3,13 @@ package protocbridge.frontend
 class WindowsPluginFrontendSpec extends OsSpecificFrontendSpec {
   if (PluginFrontend.isWindows) {
     it must "execute a program that forwards input and output to given stream" in {
-      testSuccess(WindowsPluginFrontend)
+      val state = testSuccess(WindowsPluginFrontend)
+      state.serverSocket.isClosed mustBe true
     }
 
     it must "not hang if there is an OOM in generator" in {
-      testFailure(WindowsPluginFrontend)
+      val state = testFailure(WindowsPluginFrontend)
+      state.serverSocket.isClosed mustBe true
     }
   }
 }