Refactor of AST traversal method (#944)

* Solve limitations in the current method used to traverse the AST.
The new method does not look externally (outside of NodeProcessors) but instead injects NodeSinker into the NodeProcessors so each one decides if further traversal needs to happen. This has simplified the code notably, and removes the need for specific dependency injection.

* Changes in how HTML content is generated:
  * Empty document no longer generated empty <h1></h1>
  * Empty literal no longer generated empty <pre></pre>
  * Sections are now wrapped around <div> elements for better organization.

Author: abelsromero

CHANGELOG.adoc

@@ -23,6 +23,9 @@ Improvements::
   * Added support for AsciidoctorJ v3.0.0 (#651)
   * Add compatibility with maven-site-plugin v3.20.0 and Doxia v2.0.0 (#933)
   * Add support for code blocks titles in asciidoctor-parser-doxia-module (#935)
+  * Refactor AST traversal method in asciidoctor-parser-doxia-module (#944)
+  * Empty titles in document or empty literals no longer generate <h1> or <pre> in asciidoctor-parser-doxia-module (#944)
+  * Sections are now wrapped in <div> in asciidoctor-parser-doxia-module (#944)
 
 Build / Infrastructure::
 

asciidoctor-maven-commons/src/main/java/org/asciidoctor/maven/site/HeadParser.java

@@ -9,6 +9,8 @@
  * This allows Doxia to build:
  * - breadcrumbs
  * - HTML head's meta elements
+ *
+ * @since 3.0.0
  */
 public class HeadParser {
 

asciidoctor-parser-doxia-module/src/main/java/org/asciidoctor/maven/site/parser/AsciidoctorAstDoxiaParser.java

@@ -5,6 +5,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.Reader;
+import java.util.List;
 import java.util.logging.Logger;
 
 import org.apache.maven.doxia.parser.AbstractTextParser;
@@ -28,6 +29,7 @@
 import org.asciidoctor.maven.site.SiteConversionConfiguration;
 import org.asciidoctor.maven.site.SiteConversionConfigurationParser;
 import org.asciidoctor.maven.site.SiteLogHandlerDeserializer;
+import org.asciidoctor.maven.site.parser.processors.DescriptionListNodeProcessor;
 import org.codehaus.plexus.component.annotations.Component;
 import org.codehaus.plexus.util.IOUtil;
 import org.codehaus.plexus.util.xml.Xpp3Dom;
@@ -82,7 +84,7 @@ public void parse(Reader reader, Sink sink, String reference) throws ParseExcept
         final Asciidoctor asciidoctor = Asciidoctor.Factory.create();
 
         SiteConversionConfiguration conversionConfig = new SiteConversionConfigurationParser(project)
-                .processAsciiDocConfig(siteConfig, defaultOptions(siteDirectory), defaultAttributes());
+            .processAsciiDocConfig(siteConfig, defaultOptions(siteDirectory), defaultAttributes());
         for (String require : conversionConfig.getRequires()) {
             requireLibrary(asciidoctor, require);
         }
@@ -98,7 +100,7 @@ public void parse(Reader reader, Sink sink, String reference) throws ParseExcept
         try {
             // process log messages according to mojo configuration
             new LogRecordsProcessors(logHandler, siteDirectory, errorMessage -> logger.error(errorMessage))
-                    .processLogRecords(memoryLogHandler);
+                .processLogRecords(memoryLogHandler);
 
         } catch (Exception exception) {
             throw new ParseException(exception.getMessage(), exception);
@@ -110,10 +112,8 @@ public void parse(Reader reader, Sink sink, String reference) throws ParseExcept
         new HeadParser(sink)
             .parse(headerMetadata);
 
-        sink.body();
-        final NodesSinker nodesSinker = new NodesSinker(sink);
-        nodesSinker.processNode(document);
-        sink.body_();
+        new NodeSinker(sink)
+            .sink(document);
     }
 
     private MemoryLogHandler asciidoctorLoggingSetup(Asciidoctor asciidoctor, LogHandler logHandler, File siteDirectory) {
@@ -148,15 +148,15 @@ protected File resolveSiteDirectory(MavenProject project, Xpp3Dom siteConfig) {
 
     protected OptionsBuilder defaultOptions(File siteDirectory) {
         return Options.builder()
-                .backend("xhtml")
-                .safe(SafeMode.UNSAFE)
-                .baseDir(new File(siteDirectory, ROLE_HINT));
+            .backend("xhtml")
+            .safe(SafeMode.UNSAFE)
+            .baseDir(new File(siteDirectory, ROLE_HINT));
     }
 
     protected AttributesBuilder defaultAttributes() {
         return Attributes.builder()
-                .attribute("idprefix", "@")
-                .attribute("showtitle", "@");
+            .attribute("idprefix", "@")
+            .attribute("showtitle", "@");
     }
 
     private void requireLibrary(Asciidoctor asciidoctor, String require) {

asciidoctor-parser-doxia-module/src/main/java/org/asciidoctor/maven/site/parser/NodeSinker.java

@@ -0,0 +1,66 @@
+package org.asciidoctor.maven.site.parser;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.maven.doxia.sink.Sink;
+import org.asciidoctor.ast.StructuralNode;
+import org.asciidoctor.maven.site.parser.processors.DescriptionListNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.DocumentNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.ImageNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.ListItemNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.ListingNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.LiteralNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.NoOpNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.OrderedListNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.ParagraphNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.PreambleNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.SectionNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.TableNodeProcessor;
+import org.asciidoctor.maven.site.parser.processors.UnorderedListNodeProcessor;
+
+/**
+ * Factory and repository for NodeProcessors.
+ *
+ * @author abelsromero
+ * @since 3.1.0
+ */
+public class NodeSinker {
+
+    private final List<NodeProcessor> nodeProcessors;
+
+    private final NodeProcessor noOpProcessor;
+
+    public NodeSinker(Sink sink) {
+        nodeProcessors = Arrays.asList(
+            new DescriptionListNodeProcessor(sink, this),
+            new DocumentNodeProcessor(sink, this),
+            new ImageNodeProcessor(sink, this),
+            new ListItemNodeProcessor(sink, this),
+            new ListingNodeProcessor(sink, this),
+            new ListingNodeProcessor(sink, this),
+            new LiteralNodeProcessor(sink, this),
+            new OrderedListNodeProcessor(sink, this),
+            new ParagraphNodeProcessor(sink, this),
+            new PreambleNodeProcessor(sink, this),
+            new SectionNodeProcessor(sink, this),
+            new TableNodeProcessor(sink, this),
+            new UnorderedListNodeProcessor(sink, this)
+        );
+        noOpProcessor = new NoOpNodeProcessor(sink, this);
+    }
+
+    /**
+     * Returns first NodeProcessor that can treat the node.
+     **/
+    private NodeProcessor get(StructuralNode node) {
+        return nodeProcessors.stream()
+            .filter(nodeProcessor -> nodeProcessor.applies(node))
+            .findFirst()
+            .orElse(noOpProcessor);
+    }
+
+    public void sink(StructuralNode node) {
+        get(node).process(node);
+    }
+}

asciidoctor-parser-doxia-module/src/main/java/org/asciidoctor/maven/site/parser/NodesSinker.java

@@ -2,6 +2,8 @@
 
 import org.apache.maven.doxia.sink.Sink;
 import org.asciidoctor.ast.ContentNode;
+import org.asciidoctor.ast.StructuralNode;
+import org.asciidoctor.maven.site.parser.NodeSinker;
 
 /**
  * Recommended base case to build a {@link org.asciidoctor.maven.site.parser.NodeProcessor}.
@@ -12,14 +14,17 @@
 public class AbstractSinkNodeProcessor {
 
     private final Sink sink;
+    private final NodeSinker nodeSinker;
 
     /**
      * Constructor.
      *
-     * @param sink Doxia {@link Sink}
+     * @param sink       Doxia {@link Sink}
+     * @param nodeSinker
      */
-    public AbstractSinkNodeProcessor(Sink sink) {
+    public AbstractSinkNodeProcessor(Sink sink, NodeSinker nodeSinker) {
         this.sink = sink;
+        this.nodeSinker = nodeSinker;
     }
 
     /**
@@ -31,6 +36,16 @@ protected Sink getSink() {
         return sink;
     }
 
+    /**
+     * Delegates the processing of the new node to the appropriate processor.
+     * Similar to {@link org.asciidoctor.maven.site.parser.NodeProcessor#process(StructuralNode)}
+     * but this selects the processor from the ones available.
+     *
+     * @param node Node to process
+     */
+    protected void sink(StructuralNode node) {
+        nodeSinker.sink(node);
+    }
 
     /**
      * Tests for the presence of an attribute in current and parent nodes.

asciidoctor-parser-doxia-module/src/main/java/org/asciidoctor/maven/site/parser/processors/AbstractSinkNodeProcessor.java

@@ -8,6 +8,7 @@
 import org.asciidoctor.ast.ListItem;
 import org.asciidoctor.ast.StructuralNode;
 import org.asciidoctor.maven.site.parser.NodeProcessor;
+import org.asciidoctor.maven.site.parser.NodeSinker;
 
 /**
  * Description list processor.
@@ -17,24 +18,14 @@
  */
 public class DescriptionListNodeProcessor extends AbstractSinkNodeProcessor implements NodeProcessor {
 
-    private ListItemNodeProcessor itemNodeProcessor;
-
     /**
      * Constructor.
      *
-     * @param sink Doxia {@link Sink}
-     */
-    public DescriptionListNodeProcessor(Sink sink) {
-        super(sink);
-    }
-
-    /**
-     * Inject a {@link ListItemNodeProcessor}.
-     *
-     * @param nodeProcessor {@link ListItemNodeProcessor}
+     * @param sink       Doxia {@link Sink}
+     * @param nodeSinker
      */
-    public void setItemNodeProcessor(ListItemNodeProcessor nodeProcessor) {
-        this.itemNodeProcessor = nodeProcessor;
+    public DescriptionListNodeProcessor(Sink sink, NodeSinker nodeSinker) {
+        super(sink, nodeSinker);
     }
 
     @Override
@@ -67,7 +58,7 @@ public void process(StructuralNode node) {
                 if (description.getBlocks().isEmpty()) {
                     sink.rawText(description.getText());
                 } else {
-                    itemNodeProcessor.process(description);
+                    super.sink(description);
                 }
                 sink.definition_();
             }

asciidoctor-parser-doxia-module/src/main/java/org/asciidoctor/maven/site/parser/processors/DescriptionListNodeProcessor.java

@@ -3,6 +3,9 @@
 import org.apache.maven.doxia.sink.Sink;
 import org.asciidoctor.ast.StructuralNode;
 import org.asciidoctor.maven.site.parser.NodeProcessor;
+import org.asciidoctor.maven.site.parser.NodeSinker;
+
+import static org.asciidoctor.maven.commons.StringUtils.isNotBlank;
 
 /**
  * Root document processor.
@@ -17,8 +20,8 @@ public class DocumentNodeProcessor extends AbstractSinkNodeProcessor implements
      *
      * @param sink Doxia {@link Sink}
      */
-    public DocumentNodeProcessor(Sink sink) {
-        super(sink);
+    public DocumentNodeProcessor(Sink sink, NodeSinker nodeSinker) {
+        super(sink, nodeSinker);
     }
 
     @Override
@@ -28,7 +31,18 @@ public boolean applies(StructuralNode node) {
 
     @Override
     public void process(StructuralNode node) {
-        // NOTE: H1 generation fixed in doxia 2.0.0-MX
-        getSink().rawText(String.format("<h1>%s</h1>", node.getTitle()));
+        final Sink sink = getSink();
+
+        sink.body();
+        String title = node.getTitle();
+        if (isNotBlank(title)) {
+            sink.sectionTitle1();
+            sink.rawText(title);
+            sink.sectionTitle1_();
+        }
+        node.getBlocks()
+            .forEach(this::sink);
+
+        sink.body_();
     }
 }