Fix newlines and indentation in ModelBuildingException message (#1257)

maven-model-builder/src/main/java/org/apache/maven/model/building/ModelBuildingException.java

@@ -128,7 +128,8 @@ public class ModelBuildingException extends Exception {
         return null;
     }
 
-    private static String toMessage(String modelId, List<ModelProblem> problems) {
+    // Package protected for test
+    static String toMessage(String modelId, List<ModelProblem> problems) {
         StringWriter buffer = new StringWriter(1024);
 
         PrintWriter writer = new PrintWriter(buffer);
@@ -140,17 +141,17 @@ public class ModelBuildingException extends Exception {
             writer.print(" for ");
             writer.print(modelId);
         }
-        writer.println();
 
         for (ModelProblem problem : problems) {
-            writer.print("[");
+            writer.println();
+            writer.print("    - [");
             writer.print(problem.getSeverity());
             writer.print("] ");
             writer.print(problem.getMessage());
             String location = ModelProblemUtils.formatLocation(problem, modelId);
             if (!location.isEmpty()) {
                 writer.print(" @ ");
-                writer.println(location);
+                writer.print(location);
             }
         }
 

maven-model-builder/src/test/java/org/apache/maven/model/building/ModelBuildingExceptionTest.java

@@ -0,0 +1,42 @@
+/*
+ * 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.model.building;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ModelBuildingExceptionTest {
+
+    @Test
+    void testMessage() {
+        DefaultModelProblem pb1 =
+                new DefaultModelProblem("message1", ModelProblem.Severity.ERROR, null, "source", 0, 0, "modelId", null);
+        DefaultModelProblem pb2 =
+                new DefaultModelProblem("message2", ModelProblem.Severity.ERROR, null, "source", 0, 0, "modelId", null);
+        String msg = ModelBuildingException.toMessage("modelId", Arrays.asList(pb1, pb2));
+        assertEquals(
+                "2 problems were encountered while building the effective model for modelId" + System.lineSeparator()
+                        + "    - [ERROR] message1" + System.lineSeparator()
+                        + "    - [ERROR] message2",
+                msg);
+    }
+}