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# Language Module Setup
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Core language module registration and configuration for integrating Visualforce analysis into PMD. This capability handles language registration, parser creation, and configuration management.
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## Capabilities
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### VfLanguageModule
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Main entry point for PMD's Visualforce language support. This singleton class registers the Visualforce language with PMD and provides core services.
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```java { .api }
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/**
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 * Main language module for Visualforce that extends PMD's language framework
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 * Implements CpdCapableLanguage for copy-paste detection support
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 */
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public class VfLanguageModule extends SimpleLanguageModuleBase implements CpdCapableLanguage {
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    /** Language identifier constant */
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    static final String ID = "visualforce";
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    /** Display name constant */
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    static final String NAME = "Salesforce Visualforce";
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    /**
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     * Get the singleton instance of the Visualforce language module
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     * @return VfLanguageModule instance registered with PMD
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     */
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    public static VfLanguageModule getInstance();
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    /**
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     * Create a CPD lexer for copy-paste detection in Visualforce files
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     * @param bundle Language property configuration
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     * @return CpdLexer instance for Visualforce tokenization
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     */
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    @Override
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    public CpdLexer createCpdLexer(LanguagePropertyBundle bundle);
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    /**
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     * Create a new property bundle with default Visualforce configuration
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     * @return VfLanguageProperties with default settings
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     */
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    @Override
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    public LanguagePropertyBundle newPropertyBundle();
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}
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```
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**Usage Example:**
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```java
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import net.sourceforge.pmd.lang.visualforce.VfLanguageModule;
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import net.sourceforge.pmd.lang.LanguageRegistry;
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// Get the Visualforce language module instance
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VfLanguageModule vfModule = VfLanguageModule.getInstance();
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// Check if Visualforce language is registered
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boolean isRegistered = LanguageRegistry.PMD.getLanguageById("visualforce") != null;
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// Create CPD lexer for copy-paste detection
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VfLanguageProperties properties = new VfLanguageProperties();
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CpdLexer lexer = vfModule.createCpdLexer(properties);
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```
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### VfLanguageProperties
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Configuration properties for Visualforce language analysis, including paths to Apex classes and Salesforce objects for type resolution.
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```java { .api }
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/**
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 * Language-specific properties for Visualforce analysis configuration
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 * Extends PMD's LanguagePropertyBundle with Visualforce-specific settings
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 */
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public class VfLanguageProperties extends LanguagePropertyBundle {
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    /**
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     * Directory paths containing Apex classes referenced from Visualforce pages
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     * Environment variable: PMD_VF_APEX_DIRECTORIES
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     * Default: "../classes" (relative to Visualforce directory)
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     */
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    public static final PropertyDescriptor<List<String>> APEX_DIRECTORIES_DESCRIPTOR =
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        PropertyFactory.stringListProperty("apexDirectories")
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                       .desc("Location of Apex Class directories. Absolute or relative to the Visualforce directory.")
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                       .defaultValues("../classes")
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                       .build();
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    /**
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     * Directory paths containing Custom Object definitions referenced from Visualforce pages
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     * Environment variable: PMD_VF_OBJECTS_DIRECTORIES  
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     * Default: "../objects" (relative to Visualforce directory)
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     */
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    public static final PropertyDescriptor<List<String>> OBJECTS_DIRECTORIES_DESCRIPTOR =
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        PropertyFactory.stringListProperty("objectsDirectories")
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                       .desc("Location of Custom Object directories. Absolute or relative to the Visualforce directory.")
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                       .defaultValues("../objects")
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                       .build();
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    /**
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     * Create new VfLanguageProperties with default configuration
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     */
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    public VfLanguageProperties();
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}
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```
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**Usage Example:**
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```java
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import net.sourceforge.pmd.lang.visualforce.VfLanguageProperties;
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import java.util.Arrays;
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// Create properties with default configuration
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VfLanguageProperties properties = new VfLanguageProperties();
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// Configure custom Apex directories
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properties.setProperty(VfLanguageProperties.APEX_DIRECTORIES_DESCRIPTOR, 
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    Arrays.asList("/path/to/apex/classes", "/another/apex/path"));
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// Configure custom Object directories  
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properties.setProperty(VfLanguageProperties.OBJECTS_DIRECTORIES_DESCRIPTOR,
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    Arrays.asList("/path/to/objects"));
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```
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### VfHandler
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Language version handler that provides parser instances for Visualforce analysis.
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```java { .api }
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/**
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 * Language version handler for Visualforce
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 * Implements PMD's LanguageVersionHandler interface
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 */
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public class VfHandler implements LanguageVersionHandler {
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    /**
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     * Create new handler with specified properties
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     * @param properties Configuration properties for parsing
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     */
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    public VfHandler(VfLanguageProperties properties);
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    /**
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     * Get parser instance for Visualforce content
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     * @return VfParser configured with current properties
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     */
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    @Override
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    public Parser getParser();
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}
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```
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**Usage Example:**
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```java
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import net.sourceforge.pmd.lang.visualforce.*;
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// Create language properties and handler
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VfLanguageProperties properties = new VfLanguageProperties();
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VfHandler handler = new VfHandler(properties);
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// Get parser from handler
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Parser parser = handler.getParser();
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```
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### Copy-Paste Detection
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Specialized lexer for detecting code duplication in Visualforce files.
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```java { .api }
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/**
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 * CPD lexer for Visualforce files
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 * Previously known as VfTokenizer in PMD 6
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 * Extends JavaccCpdLexer for token-based copy-paste detection
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 */
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public class VfCpdLexer extends JavaccCpdLexer {
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    /**
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     * Create token manager for Visualforce content
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     * @param doc Text document to tokenize
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     * @return TokenManager for Visualforce tokens
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     */
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    @Override
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    protected TokenManager<JavaccToken> makeLexerImpl(TextDocument doc);
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}
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```
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**Usage Example:**
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```java
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import net.sourceforge.pmd.lang.visualforce.cpd.VfCpdLexer;
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import net.sourceforge.pmd.lang.document.TextDocument;
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// Create CPD lexer for copy-paste detection
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VfCpdLexer lexer = new VfCpdLexer();
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// Use with PMD's CPD engine to detect duplicated Visualforce markup
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// (typically handled automatically by PMD framework)
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```
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## Service Registration
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The Visualforce language module is automatically registered with PMD through Java's ServiceLoader mechanism:
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- **Service file**: `META-INF/services/net.sourceforge.pmd.lang.Language`
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- **Implementation**: `net.sourceforge.pmd.lang.visualforce.VfLanguageModule`
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This enables automatic discovery and registration when the pmd-visualforce JAR is on the classpath.