Support for generic types in containers

src/main/java/picocli/CommandLine.java

@@ -4886,6 +4886,30 @@ public interface IVersionProvider {
          */
         String[] getVersion() throws Exception;
     }
+
+    /**
+     * Converter which can be used in case when picocli should use default convert. For example this can be used in maps:
+     *
+     * <pre>
+     *   class App {
+     *       &#064;Option(names = "-D", converter = {UseDefaultConverter.class, GenericValueConverter.class})
+     *       Map&lt;String, GenericValue&lt;?&gt;&gt; values;
+     *  }
+     * </pre>
+     *
+     * Instances of this class will throw UnsupportedOperationException for {@link #convert(String)} method.
+     */
+    public static final class UseDefaultConverter implements ITypeConverter<Object> {
+
+        /**
+         * Always throws UnsupportedOperationException.
+         * @throws UnsupportedOperationException always
+         */
+        public Object convert(String value) throws Exception {
+            throw new UnsupportedOperationException("This convert should never be called.");
+        }
+    }
+
     private static class NoVersionProvider implements IVersionProvider {
         public String[] getVersion() throws Exception { throw new UnsupportedOperationException(); }
     }
@@ -10889,13 +10913,16 @@ static Class<?>[] extractTypeParameters(ParameterizedType genericType) {
                     } else if (paramTypes[i] instanceof ParameterizedType) { // e.g. Optional<Integer>
                         ParameterizedType parameterizedParamType = (ParameterizedType) paramTypes[i];
                         Type raw = parameterizedParamType.getRawType();
-                        if (i == 1 && raw instanceof Class && CommandLine.isOptional((Class) raw)) { // #1108 and #1214
+                        if (raw instanceof Class) {
                             result.add((Class) raw);
-                            Class<?>[] aux = extractTypeParameters(parameterizedParamType);
-                            if (aux.length == 1) {
-                                result.add(aux[0]);
-                                continue;
+                            if (i == 1 && CommandLine.isOptional((Class) raw)) { // #1108 and #1214
+                                Class<?>[] aux = extractTypeParameters(parameterizedParamType);
+                                if (aux.length == 1) {
+                                    result.add(aux[0]);
+                                    continue;
+                                }
                             }
+                            continue;
                         }
                     } else if (paramTypes[i] instanceof WildcardType) { // e.g. ? extends Number
                         WildcardType wildcardType = (WildcardType) paramTypes[i];
@@ -14258,7 +14285,7 @@ private Collection<Object> createCollection(Class<?> collectionClass, Class<?>[]
             return (Map<Object, Object>) factory.create(mapClass);
         }
         private ITypeConverter<?> getTypeConverter(Class<?>[] types, final ArgSpec argSpec, int index) {
-            if (argSpec.converters().length > index) { return argSpec.converters()[index]; } // use custom converters if defined
+            if (argSpec.converters().length > index && !argSpec.converters()[index].getClass().equals(UseDefaultConverter.class)) { return argSpec.converters()[index]; } // use custom converters if defined
             Class<?> type = types[index];
             if (isOptional(type)) { // #1214 #1108
                 if (types.length <= index + 1) { throw new PicocliException("Cannot create converter for types " + Arrays.asList(types) + " for " + argSpec); }

src/test/java/picocli/GenericTest.java

@@ -0,0 +1,132 @@
+package picocli;
+
+import org.junit.Test;
+import picocli.CommandLine.MissingTypeConverterException;
+import picocli.CommandLine.UseDefaultConverter;
+import picocli.CommandLine.Option;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+import static picocli.CommandLine.ITypeConverter;
+import static picocli.CommandLine.Parameters;
+
+public class GenericTest {
+
+    static final class GenericValue<T> {
+        private final T value;
+
+        public GenericValue(T value) {
+            this.value = value;
+        }
+
+        public T getValue() {
+            return value;
+        }
+
+        @Override
+        public String toString() {
+            return "GenericValue{" +
+                    "value=" + value +
+                    '}';
+        }
+    }
+
+    static final class GenericValueConverter implements ITypeConverter<GenericValue<?>> {
+
+        public GenericValue<?> convert(String value) throws Exception {
+            if (value.startsWith("s")) {
+                return new GenericValue<String>(value);
+            }
+            return new GenericValue<Integer>(Integer.parseInt(value));
+        }
+    }
+
+    @Test
+    public void testListOfGenericClasses() {
+        class App {
+            @Parameters(arity = "0..*", converter = GenericValueConverter.class)
+            List<GenericValue<?>> values;
+        }
+        App app = CommandLine.populateCommand(new App(), "sOne", "15");
+        assertEquals(2, app.values.size());
+        assertEquals(String.class, app.values.get(0).value.getClass());
+        assertEquals("sOne", app.values.get(0).value);
+        assertEquals(Integer.class, app.values.get(1).value.getClass());
+        assertEquals(15, app.values.get(1).value);
+    }
+
+    @Test
+    public void testListOfGenericClassesNoConverter() {
+        class NoConverterApp {
+            @Parameters(arity = "0..*")
+            List<GenericValue<?>> values;
+        }
+        try {
+            CommandLine.populateCommand(new NoConverterApp(), "sOne", "15");
+            fail("Expected exception");
+        } catch (MissingTypeConverterException ex) {
+            assertEquals("No TypeConverter registered for picocli.GenericTest$GenericValue of field java.util.List<picocli.GenericTest$GenericValue<?>> picocli.GenericTest$1NoConverterApp.values", ex.getMessage());
+        }
+    }
+
+    @Test
+    public void testListOfGenericWithGlobalConverter() {
+        class NoConverterApp {
+            @Parameters(arity = "0..*")
+            List<GenericValue<?>> values;
+        }
+        @SuppressWarnings("rawtypes")
+        class GenericConverter implements ITypeConverter<GenericValue> {
+
+            @Override
+            public GenericValue convert(String value) throws Exception {
+                return new GenericValue<>("abc");
+            }
+        }
+        NoConverterApp app = new NoConverterApp();
+        new CommandLine(app).registerConverter(GenericValue.class, new GenericConverter()).parseArgs("xyz");
+        assertEquals(1, app.values.size());
+        assertEquals(String.class, app.values.get(0).value.getClass());
+        assertEquals("abc", app.values.get(0).value);
+    }
+
+    @Test
+    public void testMapOfGenericClasses() {
+        class App {
+            @Option(names = "-D", converter = {UseDefaultConverter.class, GenericValueConverter.class})
+            Map<String, GenericValue<?>> values;
+        }
+        App app = CommandLine.populateCommand(new App(), "-Dkey1=sOne", "-Dkey2=15");
+        assertEquals(2, app.values.size());
+        assertEquals(String.class, app.values.get("key1").value.getClass());
+        assertEquals("sOne", app.values.get("key1").value);
+        assertEquals(Integer.class, app.values.get("key2").value.getClass());
+        assertEquals(15, app.values.get("key2").value);
+    }
+
+    @Test
+    public void testSingleValueGenericWildcardClass() {
+        class App {
+            @Parameters(converter = GenericValueConverter.class)
+            GenericValue<?> value;
+        }
+        App app = CommandLine.populateCommand(new App(), "sTest");
+        assertEquals(String.class, app.value.value.getClass());
+        assertEquals("sTest", app.value.value);
+    }
+
+    @Test
+    public void testSingleValueGenericConcreteClass() {
+        class App {
+            @Parameters(converter = GenericValueConverter.class)
+            GenericValue<Integer> value;
+        }
+        App app = CommandLine.populateCommand(new App(), "3");
+        assertEquals(Integer.class, app.value.value.getClass());
+        assertEquals(Integer.valueOf(3), app.value.value);
+    }
+
+}