[MNG-8141] Model builder should report problems it finds during build (#1556)

And not rely that model was validated, which is not true in some cases. Model builder can still easily detect issues with models while building them.

Provides "escape hatch" for projects stuck on invalid models in form of user property that can be enabled with `-Dmaven.modelBuilder.failOnInvalidModel=false`, this reverts to _old_ behaviour of maven, and the JavaFX reproducer goes back to error "unable to resolve" errors with uninterpolated `${javafx.platform}` property as classifier.

---

https://issues.apache.org/jira/browse/MNG-8141

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

@@ -97,6 +97,30 @@ import static org.apache.maven.model.building.Result.newResult;
 @Named
 @Singleton
 public class DefaultModelBuilder implements ModelBuilder {
+    /**
+     * Key for "fail on invalid model" property.
+     * <p>
+     * Visible for testing.
+     */
+    static final String FAIL_ON_INVALID_MODEL = "maven.modelBuilder.failOnInvalidModel";
+
+    /**
+     * Checks user and system properties (in this order) for value of {@link #FAIL_ON_INVALID_MODEL} property key, if
+     * set and returns it. If not set, defaults to {@code true}.
+     * <p>
+     * This is only meant to provide "escape hatch" for those builds, that are for some reason stuck with invalid models.
+     */
+    private static boolean isFailOnInvalidModel(ModelBuildingRequest request) {
+        String val = request.getUserProperties().getProperty(FAIL_ON_INVALID_MODEL);
+        if (val == null) {
+            val = request.getSystemProperties().getProperty(FAIL_ON_INVALID_MODEL);
+        }
+        if (val != null) {
+            return Boolean.parseBoolean(val);
+        }
+        return true;
+    }
+
     @Inject
     private ModelProcessor modelProcessor;
 
@@ -253,6 +277,7 @@ public class DefaultModelBuilder implements ModelBuilder {
     protected ModelBuildingResult build(ModelBuildingRequest request, Collection<String> importIds)
             throws ModelBuildingException {
         // phase 1
+        boolean failOnInvalidModel = isFailOnInvalidModel(request);
         DefaultModelBuildingResult result = new DefaultModelBuildingResult();
 
         DefaultModelProblemCollector problems = new DefaultModelProblemCollector(result);
@@ -306,7 +331,7 @@ public class DefaultModelBuilder implements ModelBuilder {
             profileActivationContext.setProjectProperties(tmpModel.getProperties());
 
             Map<String, Activation> interpolatedActivations =
-                    getInterpolatedActivations(rawModel, profileActivationContext, problems);
+                    getInterpolatedActivations(rawModel, profileActivationContext, failOnInvalidModel, problems);
             injectProfileActivations(tmpModel, interpolatedActivations);
 
             List<Profile> activePomProfiles =
@@ -430,8 +455,12 @@ public class DefaultModelBuilder implements ModelBuilder {
     }
 
     private Map<String, Activation> getInterpolatedActivations(
-            Model rawModel, DefaultProfileActivationContext context, DefaultModelProblemCollector problems) {
+            Model rawModel,
-        Map<String, Activation> interpolatedActivations = getProfileActivations(rawModel, true);
+            DefaultProfileActivationContext context,
+            boolean failOnInvalidModel,
+            DefaultModelProblemCollector problems) {
+        Map<String, Activation> interpolatedActivations =
+                getProfileActivations(rawModel, true, failOnInvalidModel, problems);
 
         if (interpolatedActivations.isEmpty()) {
             return Collections.emptyMap();
@@ -753,7 +782,8 @@ public class DefaultModelBuilder implements ModelBuilder {
         }
     }
 
-    private Map<String, Activation> getProfileActivations(Model model, boolean clone) {
+    private Map<String, Activation> getProfileActivations(
+            Model model, boolean clone, boolean failOnInvalidModel, ModelProblemCollector problems) {
         Map<String, Activation> activations = new HashMap<>();
         for (Profile profile : model.getProfiles()) {
             Activation activation = profile.getActivation();
@@ -766,7 +796,11 @@ public class DefaultModelBuilder implements ModelBuilder {
                 activation = activation.clone();
             }
 
-            activations.put(profile.getId(), activation);
+            if (activations.put(profile.getId(), activation) != null) {
+                problems.add(new ModelProblemCollectorRequest(
+                                failOnInvalidModel ? Severity.FATAL : Severity.WARNING, ModelProblem.Version.BASE)
+                        .setMessage("Duplicate activation for profile " + profile.getId()));
+            }
         }
 
         return activations;
@@ -787,7 +821,8 @@ public class DefaultModelBuilder implements ModelBuilder {
 
     private Model interpolateModel(Model model, ModelBuildingRequest request, ModelProblemCollector problems) {
         // save profile activations before interpolation, since they are evaluated with limited scope
-        Map<String, Activation> originalActivations = getProfileActivations(model, true);
+        // at this stage we already failed if wanted to
+        Map<String, Activation> originalActivations = getProfileActivations(model, true, false, problems);
 
         Model interpolatedModel =
                 modelInterpolator.interpolateModel(model, model.getProjectDirectory(), request, problems);

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

@@ -18,6 +18,8 @@
  */
 package org.apache.maven.model.building;
 
+import java.io.File;
+
 import org.apache.maven.model.Dependency;
 import org.apache.maven.model.Parent;
 import org.apache.maven.model.Repository;
@@ -27,6 +29,8 @@ import org.apache.maven.model.resolution.UnresolvableModelException;
 import org.junit.Test;
 
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 /**
  * @author Guillaume Nodet
@@ -87,6 +91,38 @@ public class DefaultModelBuilderTest {
         builder.build(request);
     }
 
+    @Test
+    public void testBadProfiles() {
+        ModelBuilder builder = new DefaultModelBuilderFactory().newInstance();
+        assertNotNull(builder);
+
+        DefaultModelBuildingRequest request = new DefaultModelBuildingRequest();
+        request.setValidationLevel(ModelBuildingRequest.VALIDATION_LEVEL_MINIMAL);
+        request.setModelSource(new FileModelSource(new File("src/test/resources/poms/building/badprofiles.xml")));
+        request.setModelResolver(new BaseModelResolver());
+
+        try {
+            builder.build(request); // throw, making "pom not available"
+            fail();
+        } catch (ModelBuildingException e) {
+            assertTrue(e.getMessage().contains("Duplicate activation for profile badprofile"));
+        }
+    }
+
+    @Test
+    public void testBadProfilesCheckDisabled() throws Exception {
+        ModelBuilder builder = new DefaultModelBuilderFactory().newInstance();
+        assertNotNull(builder);
+
+        DefaultModelBuildingRequest request = new DefaultModelBuildingRequest();
+        request.getUserProperties().setProperty(DefaultModelBuilder.FAIL_ON_INVALID_MODEL, "false");
+        request.setValidationLevel(ModelBuildingRequest.VALIDATION_LEVEL_MINIMAL);
+        request.setModelSource(new FileModelSource(new File("src/test/resources/poms/building/badprofiles.xml")));
+        request.setModelResolver(new BaseModelResolver());
+
+        builder.build(request); // does not throw, old behaviour (but result may be fully off)
+    }
+
     static class CycleInImportsResolver extends BaseModelResolver {
         @Override
         public ModelSource resolveModel(Dependency dependency) throws UnresolvableModelException {

maven-model-builder/src/test/resources/poms/building/badprofiles.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+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.
+-->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>test</groupId>
+  <artifactId>test</artifactId>
+  <version>0.1-SNAPSHOT</version>
+  <packaging>pom</packaging>
+
+  <profiles>
+    <profile>
+      <id>badprofile</id>
+      <activation>
+        <activeByDefault>true</activeByDefault>
+      </activation>
+      <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+      </properties>
+    </profile>
+    <profile>
+      <id>badprofile</id>
+      <activation>
+        <file>
+          <exists>simple.xml</exists>
+        </file>
+      </activation>
+      <properties>
+        <profile.file>activated</profile.file>
+      </properties>
+    </profile>
+  </profiles>
+</project>