Consistent argsfile parsing (#1385)

* Worker --persistent_worker argsfile functionality + test

Author: wiwa

src/java/io/bazel/rulesscala/worker/Worker.java

@@ -81,7 +81,9 @@ public void checkPermission(Permission permission) {
           int code = 0;
 
           try {
-            workerInterface.work(stringListToArray(request.getArgumentsList()));
+            String[] workerArgs = stringListToArray(request.getArgumentsList());
+            String[] args = expandArgsIfArgsfile(workerArgs);
+            workerInterface.work(args);
           } catch (ExitTrapped e) {
             code = e.code;
           } catch (Exception e) {
@@ -115,15 +117,21 @@ public void checkPermission(Permission permission) {
   /** The single pass runner for ephemeral (non-persistent) worker processes */
   private static void ephemeralWorkerMain(String workerArgs[], Interface workerInterface)
       throws Exception {
-    String[] args;
-    if (workerArgs.length == 1 && workerArgs[0].startsWith("@")) {
-      args =
-          stringListToArray(
-              Files.readAllLines(Paths.get(workerArgs[0].substring(1)), StandardCharsets.UTF_8));
+    String[] args = expandArgsIfArgsfile(workerArgs);
+    workerInterface.work(args);
+  }
+
+  private static String[] expandArgsIfArgsfile(String[] allArgs) throws IOException {
+    if (allArgs.length == 1 && allArgs[0].startsWith("@")) {
+        return stringListToArray(
+                Files.readAllLines(
+                  Paths.get(allArgs[0].substring(1)),
+                  StandardCharsets.UTF_8)
+                );
+      
     } else {
-      args = workerArgs;
+      return allArgs;
     }
-    workerInterface.work(args);
   }
 
   /**

src/java/io/bazel/rulesscala/worker/WorkerTest.java

@@ -7,12 +7,18 @@
 import java.io.PipedInputStream;
 import java.io.PipedOutputStream;
 import java.io.PrintStream;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.concurrent.atomic.AtomicInteger;
 import org.junit.AfterClass;
+import org.junit.Assert;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
+import static org.junit.Assert.assertEquals;
+
 @RunWith(JUnit4.class)
 public class WorkerTest {
 
@@ -89,6 +95,42 @@ public void work(String[] args) throws Exception {
     }
   }
 
+  @Test
+  public void testPersistentWorkerArgsfile() throws Exception {
+    Path tmpFile = Files.createTempFile("testPersistentWorkerArgsfiles-args", ".txt");
+
+    try (PersistentWorkerHelper helper = new PersistentWorkerHelper()) {
+      Worker.Interface worker =
+          new Worker.Interface() {
+            @Override
+            public void work(String[] args) {
+              for (String arg : args) {
+                System.out.println(arg);
+              }
+            }
+          };
+
+      String contents = "line 1\n--flag_1\nsome arg\n";
+
+      Files.write(tmpFile, contents.getBytes(StandardCharsets.UTF_8));
+
+      WorkerProtocol.WorkRequest.newBuilder()
+          .addArguments("@" + tmpFile)
+          .build()
+          .writeDelimitedTo(helper.requestOut);
+
+      helper.runWorker(worker);
+
+      WorkerProtocol.WorkResponse response =
+          WorkerProtocol.WorkResponse.parseDelimitedFrom(helper.responseIn);
+
+      assertEquals(response.getExitCode(), 0);
+      assertEquals(response.getOutput(), contents);
+    } finally {
+      Files.deleteIfExists(tmpFile);
+    }
+  }
+
   /** A helper to manage IO when testing a persistent worker. */
   private final class PersistentWorkerHelper implements AutoCloseable {