[MNG-8150] Handle absent source/target files in transfer listener (#1575)

The PR address two issues observed in the `SimplexTransferListener` and `ConsoleMavenTransferListener`:
1. [TransferResource#getFile()](https://github.com/apache/maven-resolver/blob/master/maven-resolver-api/src/main/java/org/eclipse/aether/transfer/TransferResource.java#L170) can be null. The current `SimplexTransferListener` will break with an NPE if the `file` is not set on the resource.
2. `TransferResource` is not immutable and does not implement `equals` or `hashCode,` making its usage in collections brittle. Listener consumers are not guaranteed to reuse the same instance across listener invocations. I suggest wrapping it in an immutable identifier.

Resolves https://issues.apache.org/jira/browse/MNG-8150

 - [x] I hereby declare this contribution to be licenced under the [Apache License Version 2.0, January 2004](http://www.apache.org/licenses/LICENSE-2.0)

---

https://issues.apache.org/jira/browse/MNG-8150

maven-embedder/src/main/java/org/apache/maven/cli/transfer/ConsoleMavenTransferListener.java

@@ -31,15 +31,16 @@ import org.eclipse.aether.transfer.TransferResource;
 
 /**
  * Console download progress meter.
- *
+ * <p>
+ * This listener is not thread-safe and should be wrapped in the {@link SimplexTransferListener} in a multi-threaded scenario.
  */
 public class ConsoleMavenTransferListener extends AbstractMavenTransferListener {
 
-    private Map<TransferResource, Long> transfers = new LinkedHashMap<>();
+    private final Map<TransferResourceIdentifier, TransferResourceAndSize> transfers = new LinkedHashMap<>();
-    private FileSizeFormat format = new FileSizeFormat(Locale.ENGLISH); // use in a synchronized fashion
+    private final FileSizeFormat format = new FileSizeFormat(Locale.ENGLISH); // use in a synchronized fashion
-    private StringBuilder buffer = new StringBuilder(128); // use in a synchronized fashion
+    private final StringBuilder buffer = new StringBuilder(128); // use in a synchronized fashion
 
-    private boolean printResourceNames;
+    private final boolean printResourceNames;
     private int lastLength;
 
     public ConsoleMavenTransferListener(
@@ -65,18 +66,19 @@ public class ConsoleMavenTransferListener extends AbstractMavenTransferListener
     @Override
     public void transferProgressed(TransferEvent event) throws TransferCancelledException {
         TransferResource resource = event.getResource();
-        transfers.put(resource, event.getTransferredBytes());
+        transfers.put(
+                new TransferResourceIdentifier(resource),
+                new TransferResourceAndSize(resource, event.getTransferredBytes()));
 
         buffer.append("Progress (").append(transfers.size()).append("): ");
 
-        Iterator<Map.Entry<TransferResource, Long>> entries =
+        Iterator<TransferResourceAndSize> entries = transfers.values().iterator();
-                transfers.entrySet().iterator();
         while (entries.hasNext()) {
-            Map.Entry<TransferResource, Long> entry = entries.next();
+            TransferResourceAndSize entry = entries.next();
-            long total = entry.getKey().getContentLength();
+            long total = entry.resource.getContentLength();
-            Long complete = entry.getValue();
+            Long complete = entry.transferredBytes;
 
-            String resourceName = entry.getKey().getResourceName();
+            String resourceName = entry.resource.getResourceName();
 
             if (printResourceNames) {
                 int idx = resourceName.lastIndexOf('/');
@@ -120,7 +122,7 @@ public class ConsoleMavenTransferListener extends AbstractMavenTransferListener
 
     @Override
     public void transferSucceeded(TransferEvent event) {
-        transfers.remove(event.getResource());
+        transfers.remove(new TransferResourceIdentifier(event.getResource()));
         overridePreviousTransfer(event);
 
         super.transferSucceeded(event);
@@ -128,7 +130,7 @@ public class ConsoleMavenTransferListener extends AbstractMavenTransferListener
 
     @Override
     public void transferFailed(TransferEvent event) {
-        transfers.remove(event.getResource());
+        transfers.remove(new TransferResourceIdentifier(event.getResource()));
         overridePreviousTransfer(event);
 
         super.transferFailed(event);
@@ -144,4 +146,6 @@ public class ConsoleMavenTransferListener extends AbstractMavenTransferListener
             buffer.setLength(0);
         }
     }
+
+    private record TransferResourceAndSize(TransferResource resource, long transferredBytes) {}
 }

maven-embedder/src/main/java/org/apache/maven/cli/transfer/SimplexTransferListener.java

@@ -18,7 +18,6 @@
  */
 package org.apache.maven.cli.transfer;
 
-import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.ArrayBlockingQueue;
@@ -129,7 +128,7 @@ public final class SimplexTransferListener extends AbstractTransferListener {
                             LOGGER.warn("Invalid TransferEvent.EventType={}; ignoring it", type);
                     }
                 } catch (TransferCancelledException e) {
-                    ongoing.put(transferEvent.getResource().getFile(), Boolean.FALSE);
+                    ongoing.put(new TransferResourceIdentifier(transferEvent.getResource()), Boolean.FALSE);
                 }
             });
         }
@@ -150,17 +149,17 @@ public final class SimplexTransferListener extends AbstractTransferListener {
         }
     }
 
-    private final ConcurrentHashMap<File, Boolean> ongoing = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<TransferResourceIdentifier, Boolean> ongoing = new ConcurrentHashMap<>();
 
     @Override
     public void transferInitiated(TransferEvent event) {
-        ongoing.putIfAbsent(event.getResource().getFile(), Boolean.TRUE);
+        ongoing.putIfAbsent(new TransferResourceIdentifier(event.getResource()), Boolean.TRUE);
         put(event, false);
     }
 
     @Override
     public void transferStarted(TransferEvent event) throws TransferCancelledException {
-        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+        if (ongoing.get(new TransferResourceIdentifier(event.getResource())) == Boolean.FALSE) {
             throw new TransferCancelledException();
         }
         put(event, false);
@@ -168,7 +167,7 @@ public final class SimplexTransferListener extends AbstractTransferListener {
 
     @Override
     public void transferProgressed(TransferEvent event) throws TransferCancelledException {
-        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+        if (ongoing.get(new TransferResourceIdentifier(event.getResource())) == Boolean.FALSE) {
             throw new TransferCancelledException();
         }
         put(event, false);
@@ -176,7 +175,7 @@ public final class SimplexTransferListener extends AbstractTransferListener {
 
     @Override
     public void transferCorrupted(TransferEvent event) throws TransferCancelledException {
-        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+        if (ongoing.get(new TransferResourceIdentifier(event.getResource())) == Boolean.FALSE) {
             throw new TransferCancelledException();
         }
         put(event, false);
@@ -184,13 +183,13 @@ public final class SimplexTransferListener extends AbstractTransferListener {
 
     @Override
     public void transferSucceeded(TransferEvent event) {
-        ongoing.remove(event.getResource().getFile());
+        ongoing.remove(new TransferResourceIdentifier(event.getResource()));
         put(event, ongoing.isEmpty());
     }
 
     @Override
     public void transferFailed(TransferEvent event) {
-        ongoing.remove(event.getResource().getFile());
+        ongoing.remove(new TransferResourceIdentifier(event.getResource()));
         put(event, ongoing.isEmpty());
     }
 

maven-embedder/src/main/java/org/apache/maven/cli/transfer/TransferResourceIdentifier.java

@@ -0,0 +1,35 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.maven.cli.transfer;
+
+import java.io.File;
+
+import org.apache.maven.api.annotations.Nullable;
+import org.eclipse.aether.transfer.TransferResource;
+
+/**
+ * Immutable identifier of a {@link TransferResource}.
+ * The {@link TransferResource} is not immutable and does not implement {@code Objects#equals} and {@code Objects#hashCode} methods,
+ * making it not very suitable for usage in collections.
+ */
+record TransferResourceIdentifier(String repositoryId, String repositoryUrl, String resourceName, @Nullable File file) {
+    TransferResourceIdentifier(TransferResource resource) {
+        this(resource.getRepositoryId(), resource.getRepositoryUrl(), resource.getResourceName(), resource.getFile());
+    }
+}

maven-embedder/src/test/java/org/apache/maven/cli/transfer/SimplexTransferListenerTest.java

@@ -21,11 +21,13 @@ package org.apache.maven.cli.transfer;
 import java.io.File;
 
 import org.eclipse.aether.DefaultRepositorySystemSession;
+import org.eclipse.aether.RepositorySystemSession;
 import org.eclipse.aether.transfer.TransferCancelledException;
 import org.eclipse.aether.transfer.TransferEvent;
 import org.eclipse.aether.transfer.TransferListener;
 import org.eclipse.aether.transfer.TransferResource;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
 
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
@@ -67,17 +69,44 @@ class SimplexTransferListenerTest {
         DefaultRepositorySystemSession session = new DefaultRepositorySystemSession(h -> false); // no close handle
 
         // for technical reasons we cannot throw here, even if delegate does cancel transfer
-        listener.transferInitiated(new TransferEvent.Builder(session, resource)
+        listener.transferInitiated(event(session, resource, TransferEvent.EventType.INITIATED));
-                .setType(TransferEvent.EventType.INITIATED)
-                .build());
 
         Thread.sleep(500); // to make sure queue is processed, cancellation applied
 
         // subsequent call will cancel
         assertThrows(
                 TransferCancelledException.class,
-                () -> listener.transferStarted(new TransferEvent.Builder(session, resource)
+                () -> listener.transferStarted(event(session, resource, TransferEvent.EventType.STARTED)));
-                        .resetType(TransferEvent.EventType.STARTED)
+    }
-                        .build()));
+
+    @Test
+    void handlesAbsentTransferSource() throws InterruptedException, TransferCancelledException {
+        TransferResource resource = new TransferResource(null, null, "http://maven.org/test/test-resource", null, null);
+
+        RepositorySystemSession session = Mockito.mock(RepositorySystemSession.class);
+        TransferListener delegate = Mockito.mock(TransferListener.class);
+        SimplexTransferListener listener = new SimplexTransferListener(delegate);
+
+        TransferEvent transferInitiatedEvent = event(session, resource, TransferEvent.EventType.INITIATED);
+        TransferEvent transferStartedEvent = event(session, resource, TransferEvent.EventType.STARTED);
+        TransferEvent transferProgressedEvent = event(session, resource, TransferEvent.EventType.PROGRESSED);
+        TransferEvent transferSucceededEvent = event(session, resource, TransferEvent.EventType.SUCCEEDED);
+
+        listener.transferInitiated(transferInitiatedEvent);
+        listener.transferStarted(transferStartedEvent);
+        listener.transferProgressed(transferProgressedEvent);
+        listener.transferSucceeded(transferSucceededEvent);
+
+        Thread.sleep(500); // to make sure queue is processed, cancellation applied
+
+        Mockito.verify(delegate).transferInitiated(transferInitiatedEvent);
+        Mockito.verify(delegate).transferStarted(transferStartedEvent);
+        Mockito.verify(delegate).transferProgressed(transferProgressedEvent);
+        Mockito.verify(delegate).transferSucceeded(transferSucceededEvent);
+    }
+
+    private static TransferEvent event(
+            RepositorySystemSession session, TransferResource resource, TransferEvent.EventType type) {
+        return new TransferEvent.Builder(session, resource).setType(type).build();
     }
 }