remkop#1346 Add pathCompletionTypes attribute to CommandLine

src/main/java/picocli/CommandLine.java

@@ -150,6 +150,7 @@ public class CommandLine {
     private final Tracer tracer = new Tracer();
     private CommandSpec commandSpec;
     private final Interpreter interpreter;
+    private final Set<String> pathCompletionTypes = new HashSet<String>();
     private final IFactory factory;
 
     private Object executionResult;
@@ -229,6 +230,12 @@ private CommandLine(Object command, IFactory factory, boolean userCalled) {
         if (userCalled) { this.applyModelTransformations(); }
         commandSpec.validate();
         if (commandSpec.unmatchedArgsBindings().size() > 0) { setUnmatchedArgumentsAllowed(true); }
+        registerDefaultPathCompletionTypes();
+    }
+
+    private void registerDefaultPathCompletionTypes() {
+        pathCompletionTypes.add("java.io.File");
+        pathCompletionTypes.add("java.nio.file.Path");
     }
 
     /** Apply transformers to command spec recursively. */
@@ -253,6 +260,8 @@ private CommandLine copy() {
 
         result.interpreter.converterRegistry.clear();
         result.interpreter.converterRegistry.putAll(interpreter.converterRegistry);
+        result.pathCompletionTypes.clear();
+        result.pathCompletionTypes.addAll(pathCompletionTypes);
         return result;
     }
 
@@ -3277,6 +3286,39 @@ public <K> CommandLine registerConverter(Class<K> cls, ITypeConverter<K> convert
         return this;
     }
 
+    /**
+     * <p>Adds the type {@code type} to the list of supported type for path completion.</p>
+     * <p>Built-in supported types being:
+     * <ul>
+     *   <li>{@link java.io.File}</li>
+     *   <li>{@link java.nio.file.Path}</li>
+     * </ul>
+     * </p>
+     * type {@code type}.
+     * @param type the type to check if path completion is supported for
+     * @return this CommandLine object, to allow method chaining
+     * @see #supportsPathCompletion(Class)
+     */
+    public <K> CommandLine registerForPathCompletion(Class<K> cls) {
+        pathCompletionTypes.add(cls.getName());
+        for (CommandLine command : getCommandSpec().commands.values()) {
+            command.registerForPathCompletion(cls);
+        }
+        return this;
+    }
+
+    /**
+     * Returns {@code true} if the CommandLine supports path completion for {@link Option} and {@link Parameters} of
+     * type {@code type}.
+     * @param type the type to check if path completion is supported for
+     * @return {@code true} if the CommandLine supports path completion for {@link Option} and {@link Parameters} of
+     * type {@code type}.
+     * @see #registerForPathCompletion(Class)
+     */
+    public boolean supportsPathCompletion(Class<?> type) {
+        return pathCompletionTypes.contains(type.getName());
+    }
+
     /** Returns the String that separates option names from option values when parsing command line options.
      * @return the String the parser uses to separate option names from option values
      * @see ParserSpec#separator() */