[MNG-8177] Add contextual info for model warnings

maven-resolver-provider/src/main/java/org/apache/maven/repository/internal/DefaultArtifactDescriptorReader.java

@@ -294,10 +294,11 @@ private Model loadPom(
                 if (!modelResult.getProblems().isEmpty()) {
                     List<ModelProblem> problems = modelResult.getProblems();
                     logger.warn(
-                            "{} {} encountered while building the effective model for {}",
+                            "{} {} encountered while building the effective model for {}; trace: {}",
                             problems.size(),
                             (problems.size() == 1) ? "problem was" : "problems were",
-                            request.getArtifact());
+                            request.getArtifact(),
+                            RequestTraceHelper.interpretTrace(true, request.getTrace()));
                     if (logger.isDebugEnabled()) {
                         for (ModelProblem problem : problems) {
                             logger.warn(

maven-resolver-provider/src/main/java/org/apache/maven/repository/internal/RequestTraceHelper.java

@@ -0,0 +1,70 @@
+/*
+ * 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.repository.internal;
+
+import java.util.stream.Collectors;
+
+import org.apache.maven.model.Plugin;
+import org.eclipse.aether.RequestTrace;
+import org.eclipse.aether.collection.CollectRequest;
+import org.eclipse.aether.collection.CollectStepData;
+import org.eclipse.aether.resolution.ArtifactDescriptorRequest;
+import org.eclipse.aether.resolution.ArtifactRequest;
+import org.eclipse.aether.resolution.DependencyRequest;
+
+/**
+ * Helper class to manage {@link RequestTrace} for better error logging.
+ *
+ * @since 3.9.9
+ */
+public final class RequestTraceHelper {
+
+    /**
+     * Method that creates some informational string based on passed in {@link RequestTrace}. The contents of request
+     * trace can literally be anything, but this class tries to cover "most common" cases that are happening in Maven.
+     */
+    public static String interpretTrace(boolean explain, RequestTrace requestTrace) {
+        while (requestTrace != null) {
+            Object data = requestTrace.getData();
+            if (data instanceof DependencyRequest) {
+                DependencyRequest request = (DependencyRequest) data;
+                return (explain ? "dependency request for " : "") + request;
+            } else if (data instanceof CollectRequest) {
+                CollectRequest request = (CollectRequest) data;
+                return (explain ? "collect request for " : "") + request;
+            } else if (data instanceof CollectStepData) {
+                CollectStepData stepData = (CollectStepData) data;
+                return (explain ? "collect path " : "")
+                        + stepData.getPath().stream().map(Object::toString).collect(Collectors.joining(" -> "));
+            } else if (data instanceof ArtifactDescriptorRequest) {
+                ArtifactDescriptorRequest request = (ArtifactDescriptorRequest) data;
+                return (explain ? "artifact descriptor request for " : "") + request.getArtifact();
+            } else if (data instanceof ArtifactRequest) {
+                ArtifactRequest request = (ArtifactRequest) data;
+                return (explain ? "artifact request for " : "") + request.getArtifact();
+            } else if (data instanceof Plugin) {
+                Plugin plugin = (Plugin) data;
+                return (explain ? "plugin " : "") + plugin.getId();
+            }
+            requestTrace = requestTrace.getParent();
+        }
+
+        return "n/a";
+    }
+}