Implement maven pom javac release option hint (JEP 247).

 - converts matching source/target options to the release option
 - supports properties and the standard maven-compiler-plugin
 - offers only hints when source/release is set to at least 9+

java/maven.hints/src/org/netbeans/modules/maven/hints/layer.xml

@@ -62,6 +62,9 @@
         <file name="org-netbeans-modules-maven-hints-pom-CompilerPluginVersionError.instance">
             <attr name="position" intvalue="1100"/>
         </file>
+        <file name="org-netbeans-modules-maven-hints-pom-UseReleaseOptionHint.instance">
+            <attr name="position" intvalue="1200"/>
+        </file>
     </folder>
 
 

java/maven.hints/src/org/netbeans/modules/maven/hints/pom/UseReleaseOptionHint.java

@@ -0,0 +1,241 @@
+/*
+ * 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.netbeans.modules.maven.hints.pom;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.prefs.Preferences;
+import javax.swing.JComponent;
+import javax.xml.namespace.QName;
+import org.netbeans.api.project.Project;
+import org.netbeans.modules.editor.NbEditorUtilities;
+import org.netbeans.modules.maven.hints.pom.spi.Configuration;
+import org.netbeans.modules.maven.hints.pom.spi.POMErrorFixProvider;
+import org.netbeans.modules.maven.model.pom.Build;
+import org.netbeans.modules.maven.model.pom.POMComponent;
+import org.netbeans.modules.maven.model.pom.POMExtensibilityElement;
+import org.netbeans.modules.maven.model.pom.POMModel;
+import org.netbeans.modules.maven.model.pom.POMQName;
+import org.netbeans.modules.maven.model.pom.Plugin;
+import org.netbeans.modules.maven.model.pom.PluginExecution;
+import org.netbeans.modules.maven.model.pom.Properties;
+import org.netbeans.spi.editor.hints.ChangeInfo;
+import org.netbeans.spi.editor.hints.ErrorDescription;
+import org.netbeans.spi.editor.hints.ErrorDescriptionFactory;
+import org.netbeans.spi.editor.hints.Fix;
+import org.netbeans.spi.editor.hints.Severity;
+import org.openide.text.Line;
+import org.openide.util.NbBundle;
+
+import static org.netbeans.modules.maven.hints.pom.Bundle.*;
+
+/**
+ * Converts source/target javac options to the release option where possible (JEP 247).
+ * @author mbien
+ */
+@NbBundle.Messages({
+    "TIT_UseReleaseVersionHint=Convert matching source/target javac options to the release option.",
+    "DESC_UseReleaseVersionHint=Matching source/target options can be replaced with a single release option (JEP 247). This enforces API compatibility with the chosen Java release.",
+    "FIX_UseReleaseVersionHint=Convert to release option for strict compatibility checks."})
+public class UseReleaseOptionHint implements POMErrorFixProvider {
+
+    private static final String TARGET_TAG = "target";
+    private static final String SOURCE_TAG = "source";
+    private static final String RELEASE_TAG = "release";
+
+    private static final Configuration config = new Configuration(UseReleaseOptionHint.class.getName(),
+                TIT_UseReleaseVersionHint(), DESC_UseReleaseVersionHint(), true, Configuration.HintSeverity.WARNING);
+
+    @Override
+    public List<ErrorDescription> getErrorsForDocument(POMModel model, Project prj) {
+
+        List<ErrorDescription> hints = new ArrayList<>();
+
+        Build build = model.getProject().getBuild();
+        if (build != null) {
+            for (Plugin plugin : build.getPlugins()) {
+                if ("maven-compiler-plugin".equals(plugin.getArtifactId())) {
+                    if (!isPluginCompatible(plugin)) {
+                        return Collections.emptyList();
+                    }
+                    if (plugin.getConfiguration() != null) {
+                        hints.addAll(createHintsForParent("", plugin.getConfiguration()));
+                    }
+                    if (plugin.getExecutions() != null) {
+                        for (PluginExecution execution : plugin.getExecutions()) {
+                            if (execution.getConfiguration() != null) {
+                                hints.addAll(createHintsForParent("", execution.getConfiguration()));
+                            }
+                        }
+                    }
+                    break;
+                }
+            }
+        }
+
+        Properties properties = model.getProject().getProperties();
+        if (properties != null) {
+            hints.addAll(createHintsForParent("maven.compiler.", properties));
+        }
+
+        return hints;
+    }
+
+    private List<ErrorDescription> createHintsForParent(String prefix, POMComponent parent) {
+
+        int source;
+        int target;
+
+        // property name or an int value
+        String release = null;
+
+        try {
+            String sourceText = parent.getChildElementText(POMQName.createQName(prefix+SOURCE_TAG, true));
+            if (isProperty(sourceText)) {
+                release = sourceText;
+                sourceText = getProperty(sourceText, parent.getModel());
+            }
+
+            String targetText = parent.getChildElementText(POMQName.createQName(prefix+TARGET_TAG, true));
+            if (isProperty(targetText)) {
+                release = targetText;
+                targetText = getProperty(targetText, parent.getModel());
+            }
+
+            source = Integer.parseInt(sourceText);
+            target = Integer.parseInt(targetText);
+            if (release == null) {
+                release = String.valueOf(target);
+            }
+        } catch (NumberFormatException ignored) {
+            return Collections.emptyList();
+        }
+
+        if (source == target && source >= 9) {
+            List<ErrorDescription> hints = new ArrayList<>();
+            for (POMComponent prop : parent.getChildren()) {
+                String name = prop.getPeer().getNodeName();
+                if (name.equals(prefix+SOURCE_TAG) || name.equals(prefix+TARGET_TAG)) {
+                    hints.add(createHintForComponent(prefix, prop, parent.getModel(), release));
+                }
+            }
+            return hints;
+        }
+        return Collections.emptyList();
+    }
+
+    private ErrorDescription createHintForComponent(String prefix, POMComponent component, POMModel model, String release) {
+        Line line = NbEditorUtilities.getLine(model.getBaseDocument(), component.findPosition(), false);
+        List<Fix> fix = Collections.singletonList(new ConvertToReleaseOptionFix(prefix, release, component));
+        return ErrorDescriptionFactory.createErrorDescription(Severity.HINT, FIX_UseReleaseVersionHint(), fix, model.getBaseDocument(), line.getLineNumber()+1);
+    }
+
+    /**
+     * maven-compiler-plugin version must be >= 3.6
+     */
+    private boolean isPluginCompatible(Plugin plugin) {
+        String string = plugin.getVersion();
+        if (string == null) {
+            return false;
+        }
+        String[] version = string.split("-")[0].split("\\.");
+        try {
+            int major = version.length > 0 ? Integer.parseInt(version[0]) : 0;
+            int minor = version.length > 1 ? Integer.parseInt(version[1]) : 0;
+            if (major < 3 || (major == 3 && minor < 6)) {
+                return false;
+            }
+        } catch (NumberFormatException ignored) {
+            return false;
+        }
+        return true;
+    }
+
+    private static boolean isProperty(String property) {
+        return property != null && property.startsWith("$");
+    }
+
+    private static String getProperty(String prop, POMModel model) {
+        if (prop.length() > 3) {
+            Properties properties = model.getProject().getProperties();
+            if (properties != null) {
+                return properties.getProperty(prop.substring(2, prop.length()-1));
+            }
+        }
+        return null;
+    }
+
+    private static class ConvertToReleaseOptionFix implements Fix {
+
+        private final String prefix;
+        private final String release;
+        private final POMComponent component;
+
+        private ConvertToReleaseOptionFix(String prefix, String release, POMComponent component) {
+            this.prefix = prefix;
+            this.component = component;
+            this.release = release;
+        }
+
+        @Override
+        public ChangeInfo implement() throws Exception {
+            ChangeInfo info = new ChangeInfo();
+            POMModel model = component.getModel();
+            PomModelUtils.implementInTransaction(model, () -> {
+                POMComponent parent = component.getParent();
+                for (POMComponent child : parent.getChildren()) {
+                    String name = child.getPeer().getNodeName();
+                    if (name.equals(prefix+SOURCE_TAG) || name.equals(prefix+TARGET_TAG)) {
+                        parent.removeExtensibilityElement((POMExtensibilityElement) child);
+                    }
+                }
+                POMExtensibilityElement element = model.getFactory().createPOMExtensibilityElement(QName.valueOf(prefix+RELEASE_TAG));
+                element.setElementText(release);
+                parent.addExtensibilityElement(element);
+            });
+            return info;
+        }
+
+        @Override
+        public String getText() {
+            return FIX_UseReleaseVersionHint();
+        }
+
+    }
+
+    @Override
+    public void cancel() {}
+
+    @Override
+    public Configuration getConfiguration() {
+        return config;
+    }
+
+    @Override
+    public String getSavedValue(JComponent customizer, String key) {
+        return null;
+    }
+
+    @Override
+    public JComponent getCustomizer(Preferences preferences) {
+        return null;
+    }
+
+}