Allow to skip generating empty report

src/main/java/org/codehaus/mojo/taglist/FileAnalyser.java

@@ -25,6 +25,7 @@
 import java.io.InputStreamReader;
 import java.io.LineNumberReader;
 import java.io.Reader;
+import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -33,7 +34,6 @@
 
 import org.apache.commons.lang.StringUtils;
 import org.apache.maven.plugin.logging.Log;
-import org.apache.maven.reporting.MavenReportException;
 import org.codehaus.mojo.taglist.beans.FileReport;
 import org.codehaus.mojo.taglist.beans.TagReport;
 import org.codehaus.mojo.taglist.tags.TagClass;
@@ -105,11 +105,6 @@ public class FileAnalyser {
      */
     private final boolean emptyCommentsOn;
 
-    /**
-     * String used to indicate that there is no comment after the tag.
-     */
-    private final String noCommentString;
-
     /**
      * ArrayList of tag classes.
      */
@@ -128,7 +123,6 @@ public FileAnalyser(TagListReport report, List<TagClass> tagClasses) {
         sourceDirs = report.getSourceDirs();
         encoding = report.getInputEncoding();
         locale = report.getLocale();
-        noCommentString = report.getBundle().getString("report.taglist.nocomment");
         this.tagClasses = tagClasses;
         this.includes = report.getIncludesCommaSeparated();
         this.excludes = report.getExcludesCommaSeparated();
@@ -138,9 +132,8 @@ public FileAnalyser(TagListReport report, List<TagClass> tagClasses) {
      * Execute the analysis for the configuration given by the TagListReport.
      *
      * @return a collection of TagReport objects.
-     * @throws MavenReportException the Maven report exception.
      */
-    public Collection<TagReport> execute() throws MavenReportException {
+    public Collection<TagReport> execute() {
         List<File> fileList = findFilesToScan();
 
         for (File file : fileList) {
@@ -162,16 +155,16 @@ public Collection<TagReport> execute() throws MavenReportException {
      * Gives the list of files to scan.
      *
      * @return a List of File objects.
-     * @throws MavenReportException the Maven report exception.
      */
-    private List<File> findFilesToScan() throws MavenReportException {
+    private List<File> findFilesToScan() {
         List<File> filesList = new ArrayList<>();
         try {
             for (String sourceDir : sourceDirs) {
                 filesList.addAll(FileUtils.getFiles(new File(sourceDir), includes, excludes));
             }
         } catch (IOException e) {
-            throw new MavenReportException("Error while trying to find the files to scan.", e);
+            // TODO - fix with Doxia 2.x - canGenerateReport will have a checked exception
+            throw new UncheckedIOException("Error while trying to find the files to scan.", e);
         }
         return filesList;
     }
@@ -219,11 +212,7 @@ public void scanFile(File file) {
                         firstLine = StringUtils.removeEnd(firstLine, "*/"); // MTAGLIST-35
                         if (firstLine.isEmpty() || ":".equals(firstLine)) {
                             // this is not a valid comment tag: nothing is written there
-                            if (emptyCommentsOn) {
-                                comment.append("--");
-                                comment.append(noCommentString);
-                                comment.append("--");
-                            } else {
+                            if (!emptyCommentsOn) {
                                 continue;
                             }
                         } else {

src/main/java/org/codehaus/mojo/taglist/ReportGenerator.java

@@ -253,9 +253,13 @@ private void doFileDetailedPart(FileReport fileReport) {
     private void doCommentLine(FileReport fileReport, Integer lineNumber) {
         boolean linked = false;
 
+        String comment = fileReport.getComment(lineNumber);
+        if (comment == null || comment.isEmpty()) {
+            comment = "--" + bundle.getString("report.taglist.nocomment") + "--";
+        }
         sink.tableRow();
         sink.tableCell();
-        sink.text(fileReport.getComment(lineNumber));
+        sink.text(comment);
         sink.tableCell_();
         sink.tableCell();
         if (xrefLocation != null) {

src/main/java/org/codehaus/mojo/taglist/TagListReport.java

@@ -31,7 +31,6 @@
 import java.util.ResourceBundle;
 import java.util.concurrent.atomic.AtomicReference;
 
-import org.apache.maven.doxia.siterenderer.Renderer;
 import org.apache.maven.model.ReportPlugin;
 import org.apache.maven.plugins.annotations.Mojo;
 import org.apache.maven.plugins.annotations.Parameter;
@@ -70,7 +69,10 @@ public class TagListReport extends AbstractMavenReport {
     @Parameter(property = "sourceFileLocale", defaultValue = "en")
     private String sourceFileLocale;
 
-    /** Default locale used if the source file locale is null. */
+    /**
+     * Default locale used if the source file locale is null.
+     */
+    // TODO - please review default locale with Doxia 2.x
     private static final String DEFAULT_LOCALE = "en";
 
     /**
@@ -100,7 +102,6 @@ public class TagListReport extends AbstractMavenReport {
     /**
      * This parameter indicates whether for simple tags (like "TODO"), the analyzer should look for multiple line
      * comments.
-     *
      */
     @Parameter(defaultValue = "true")
     private boolean multipleLineComments;
@@ -191,13 +192,24 @@ public class TagListReport extends AbstractMavenReport {
 
     private String[] tags;
 
+    /**
+     * Skip generating report if no tags found in sources.
+     *
+     * @since 3.1.0
+     */
+    @Parameter(property = "taglist.skipEmptyReport", defaultValue = "false")
+    private boolean skipEmptyReport;
+
     private final AtomicReference<List<String>> sourceDirs = new AtomicReference<>();
 
+    private Collection<TagReport> tagReportsResult;
+
     /**
      * {@inheritDoc}
      *
      * @see org.apache.maven.reporting.AbstractMavenReport#executeReport(java.util.Locale)
      */
+    @Override
     protected void executeReport(Locale locale) throws MavenReportException {
         this.currentLocale = locale;
 
@@ -206,6 +218,47 @@ protected void executeReport(Locale locale) throws MavenReportException {
                     + Charset.defaultCharset().displayName() + ", i.e. build is platform dependent!");
         }
 
+        executeAnalysis();
+
+        // Renders the report
+        ReportGenerator generator = new ReportGenerator(this, tagReportsResult);
+        if (linkXRef) {
+            String relativePath = getRelativePath(xrefLocation);
+            if (xrefLocation.exists()) {
+                // XRef was already generated by manual execution of a lifecycle binding
+                generator.setXrefLocation(relativePath);
+                generator.setTestXrefLocation(getRelativePath(testXrefLocation));
+            } else {
+                // Not yet generated - check if the report is on its way
+
+                for (ReportPlugin report :
+                        getProject().getModel().getReporting().getPlugins()) {
+                    String artifactId = report.getArtifactId();
+                    if ("maven-jxr-plugin".equals(artifactId) || "jxr-maven-plugin".equals(artifactId)) {
+                        getLog().error("Taglist plugin MUST be executed after the JXR plugin."
+                                + "  No links to xref were generated.");
+                    }
+                }
+            }
+
+            // TODO we have similar code in many plugins to generate xref links
+            // we can externalize it to one place
+            if (generator.getXrefLocation() == null) {
+                getLog().warn("Unable to locate Source XRef to link to - DISABLED");
+            }
+        }
+        generator.generateReport();
+
+        // Generate the XML report
+        generateXmlReport(tagReportsResult);
+    }
+
+    private void executeAnalysis() {
+        if (tagReportsResult != null) {
+            // already analyzed
+            return;
+        }
+
         // Create the tag classes
         List<TagClass> tagClasses = new ArrayList<>();
 
@@ -256,37 +309,7 @@ protected void executeReport(Locale locale) throws MavenReportException {
 
         // let's proceed to the analysis
         FileAnalyser fileAnalyser = new FileAnalyser(this, tagClasses);
-        Collection<TagReport> tagReports = fileAnalyser.execute();
-
-        // Renders the report
-        ReportGenerator generator = new ReportGenerator(this, tagReports);
-        if (linkXRef) {
-            String relativePath = getRelativePath(xrefLocation);
-            if (xrefLocation.exists()) {
-                // XRef was already generated by manual execution of a lifecycle binding
-                generator.setXrefLocation(relativePath);
-                generator.setTestXrefLocation(getRelativePath(testXrefLocation));
-            } else {
-                // Not yet generated - check if the report is on its way
-
-                for (ReportPlugin report :
-                        getProject().getModel().getReporting().getPlugins()) {
-                    String artifactId = report.getArtifactId();
-                    if ("maven-jxr-plugin".equals(artifactId) || "jxr-maven-plugin".equals(artifactId)) {
-                        getLog().error("Taglist plugin MUST be executed after the JXR plugin."
-                                + "  No links to xref were generated.");
-                    }
-                }
-            }
-
-            if (generator.getXrefLocation() == null) {
-                getLog().warn("Unable to locate Source XRef to link to - DISABLED");
-            }
-        }
-        generator.generateReport();
-
-        // Generate the XML report
-        generateXmlReport(tagReports);
+        tagReportsResult = fileAnalyser.execute();
     }
 
     private TagClass createTagClass(String tag) {
@@ -372,12 +395,19 @@ private String getRelativePath(File location) {
      *
      * @see org.apache.maven.reporting.MavenReport#canGenerateReport()
      */
+    @Override
     public boolean canGenerateReport() {
         boolean canGenerate = !getSourceDirs().isEmpty();
         if (aggregate && !getProject().isExecutionRoot()) {
             canGenerate = false;
         }
-        return canGenerate;
+
+        if (canGenerate) {
+            executeAnalysis();
+            return !skipEmptyReport || tagReportsResult.stream().anyMatch(tagReport -> tagReport.getTagCount() > 0);
+        }
+
+        return false;
     }
 
     /**
@@ -401,7 +431,7 @@ private List<String> pruneSourceDirs(List<String> sourceDirectories) throws IOEx
      *
      * @param dir the source directory.
      * @return true if the folder or one of its subfolders contains at least 1 source file that matches
-     * includes/excludes.
+     *         includes/excludes.
      */
     private boolean hasSources(File dir) throws IOException {
         if (dir.exists() && dir.isDirectory()) {
@@ -537,20 +567,12 @@ public boolean isShowEmptyDetails() {
         return showEmptyDetails;
     }
 
-    /**
-     * {@inheritDoc}
-     *
-     * @see org.apache.maven.reporting.AbstractMavenReport#getSiteRenderer()
-     */
-    protected Renderer getSiteRenderer() {
-        return siteRenderer;
-    }
-
     /**
      * {@inheritDoc}
      *
      * @see org.apache.maven.reporting.AbstractMavenReport#getOutputDirectory()
      */
+    @Override
     protected String getOutputDirectory() {
         return outputDirectory.getAbsolutePath();
     }
@@ -569,6 +591,7 @@ protected String getXMLOutputDirectory() {
      *
      * @see org.apache.maven.reporting.MavenReport#getDescription(java.util.Locale)
      */
+    @Override
     public String getDescription(Locale locale) {
         return getBundle(locale).getString("report.taglist.description");
     }
@@ -578,6 +601,7 @@ public String getDescription(Locale locale) {
      *
      * @see org.apache.maven.reporting.MavenReport#getName(java.util.Locale)
      */
+    @Override
     public String getName(Locale locale) {
         return getBundle(locale).getString("report.taglist.name");
     }
@@ -587,6 +611,7 @@ public String getName(Locale locale) {
      *
      * @see org.apache.maven.reporting.MavenReport#getOutputName()
      */
+    @Override
     public String getOutputName() {
         return "taglist";
     }

src/test/java/org/codehaus/mojo/taglist/TaglistMojoBasicConfigTest.java

@@ -127,11 +127,9 @@ public void testEmptyCommentsDisabled() throws Exception {
 
         mojo.execute();
 
-        String htmlString = super.getGeneratedOutput(mojo);
-
-        // Check to see that there was zero tags found
-        String expected = "<td>@empty_comment</td><td>0</td>";
-        assertTrue("Missing tag result.", htmlString.contains(expected));
+        File outputDirectory = mojo.getReportOutputDirectory();
+        assertNotNull(outputDirectory);
+        assertFalse(outputDirectory.exists());
     }
 
     /**

src/test/java/org/codehaus/mojo/taglist/TaglistMojoSkipTest.java

@@ -0,0 +1,20 @@
+package org.codehaus.mojo.taglist;
+
+import java.io.File;
+
+public class TaglistMojoSkipTest extends AbstractTaglistMojoTestCase {
+
+    public void testNoSourcesDirectory() throws Exception {
+        File pluginXmlFile = new File(getBasedir(), "src/test/resources/unit/no-sources-test/default-pom.xml");
+
+        TagListReport mojo = super.getTagListReport(pluginXmlFile);
+
+        // Run the TagList mojo
+        mojo.execute();
+
+        // output should not be generated
+        File outputDirectory = mojo.getReportOutputDirectory();
+        assertNotNull(outputDirectory);
+        assertFalse(outputDirectory.exists());
+    }
+}

src/test/java/org/codehaus/mojo/taglist/TaglistMojoTagsTest.java

@@ -170,11 +170,9 @@ public void testNotAtStartOfLineTags() throws Exception {
         // Run the TagList mojo
         mojo.execute();
 
-        String htmlString = super.getGeneratedOutput(mojo);
-
-        // Check to see a tag not at the start of a line does not show up.
-        String expected = "<td>not_start_of_line_tag</td><td>0</td>";
-        assertTrue("Incorrect tag not at start of line tag result.", htmlString.contains(expected));
+        File outputDirectory = mojo.getReportOutputDirectory();
+        assertNotNull(outputDirectory);
+        assertFalse(outputDirectory.exists());
     }
 
     /**
@@ -193,10 +191,8 @@ public void testSourceCodeVariablesTags() throws Exception {
         // Run the TagList mojo
         mojo.execute();
 
-        String htmlString = super.getGeneratedOutput(mojo);
-
-        // Check to see a source code variable does not show up.
-        String expected = "<td>source_code_variable_tag</td><td>0</td>";
-        assertTrue("Incorrect source code variable tag result.", htmlString.contains(expected));
+        File outputDirectory = mojo.getReportOutputDirectory();
+        assertNotNull(outputDirectory);
+        assertFalse(outputDirectory.exists());
     }
 }