[CLI-323] Added Supplier<T> defaults for getParsedOptionValue (#229)

* Added Supplier<T> defaults for getParsedOptionValue

* added tests

* Fixed test issues

* fixed style issues and added test for null supplier

* added additional supplier testing

Author: Claudenw

src/main/java/org/apache/commons/cli/CommandLine.java

@@ -412,6 +412,21 @@ public <T> T getParsedOptionValue(final char opt, final T defaultValue) throws P
         return getParsedOptionValue(String.valueOf(opt), defaultValue);
     }
 
+    /**
+     * Gets a version of this {@code Option} converted to a particular type.
+     *
+     * @param opt the name of the option.
+     * @param defaultValue the default value to return if opt is not set.
+     * @param <T> The return type for the method.
+     * @return the value parsed into a particular object.
+     * @throws ParseException if there are problems turning the option value into the desired type
+     * @see PatternOptionBuilder
+     * @since 1.7.0
+     */
+    public <T> T getParsedOptionValue(final char opt, final Supplier<T> defaultValue) throws ParseException {
+        return getParsedOptionValue(String.valueOf(opt), defaultValue);
+    }
+
     /**
      * Gets a version of this {@code Option} converted to a particular type.
      *
@@ -423,7 +438,7 @@ public <T> T getParsedOptionValue(final char opt, final T defaultValue) throws P
      * @since 1.5.0
      */
     public <T> T getParsedOptionValue(final Option option) throws ParseException {
-        return  getParsedOptionValue(option, null);
+        return  getParsedOptionValue(option, () -> null);
     }
 
     /**
@@ -437,15 +452,30 @@ public <T> T getParsedOptionValue(final Option option) throws ParseException {
      * @see PatternOptionBuilder
      * @since 1.7.0
      */
-    @SuppressWarnings("unchecked")
     public <T> T getParsedOptionValue(final Option option, final T defaultValue) throws ParseException {
-        if (option == null) {
-            return null;
-        }
-        final String res = getOptionValue(option);
+        return getParsedOptionValue(option, () -> defaultValue);
+    }
+
+    /**
+     * Gets a version of this {@code Option} converted to a particular type.
+     *
+     * @param option the name of the option.
+     * @param defaultValue the default value to return if opt is not set.
+     * @param <T> The return type for the method.
+     * @return the value parsed into a particular object.
+     * @throws ParseException if there are problems turning the option value into the desired type
+     * @see PatternOptionBuilder
+     * @since 1.7.0
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T getParsedOptionValue(final Option option, final Supplier<T> defaultValue) throws ParseException {
+        final String res = option == null ? null : getOptionValue(option);
 
         try {
-            return res == null ? defaultValue : (T) option.getConverter().apply(res);
+            if (res == null) {
+                return defaultValue == null ? null : defaultValue.get();
+            }
+            return (T) option.getConverter().apply(res);
         } catch (final Throwable e) {
             throw ParseException.wrap(e);
         }
@@ -480,6 +510,21 @@ public <T> T getParsedOptionValue(final String opt, final T defaultValue) throws
         return getParsedOptionValue(resolveOption(opt), defaultValue);
     }
 
+    /**
+     * Gets a version of this {@code Option} converted to a particular type.
+     *
+     * @param opt the name of the option.
+     * @param defaultValue the default value to return if opt is not set.
+     * @param <T> The return type for the method.
+     * @return the value parsed into a particular object.
+     * @throws ParseException if there are problems turning the option value into the desired type
+     * @see PatternOptionBuilder
+     * @since 1.7.0
+     */
+    public <T> T getParsedOptionValue(final String opt, final Supplier<T> defaultValue) throws ParseException {
+        return getParsedOptionValue(resolveOption(opt), defaultValue);
+    }
+
     /**
      * jkeyes - commented out until it is implemented properly
      * <p>

src/test/java/org/apache/commons/cli/CommandLineTest.java

@@ -22,6 +22,7 @@ Licensed to the Apache Software Foundation (ASF) under one or more
 import static org.junit.Assert.assertNull;
 
 import java.util.Properties;
+import java.util.function.Supplier;
 
 import org.junit.Test;
 
@@ -166,7 +167,40 @@ public void testGetParsedOptionValueWithOption() throws Exception {
     }
 
     @Test
-    public void testNullhOption() throws Exception {
+    public void testGetParsedOptionValueUsingDefault() throws Exception {
+        final Options options = new Options();
+        final Option optI = Option.builder("i").hasArg().type(Number.class).build();
+        final Option optF = Option.builder("f").hasArg().build();
+        options.addOption(optI);
+        options.addOption(optF);
+
+        final CommandLineParser parser = new DefaultParser();
+        final CommandLine cmd = parser.parse(options, new String[] {"-i", "123"});
+        final Supplier<String> nullSupplier = null;
+
+        assertEquals(123, ((Number) cmd.getParsedOptionValue(optI)).intValue());
+        assertEquals("foo", cmd.getParsedOptionValue(optF, "foo"));
+        assertEquals("foo", cmd.getParsedOptionValue(optF, () -> "foo"));
+        assertNull(cmd.getParsedOptionValue(optF, null));
+        assertNull(cmd.getParsedOptionValue(optF, nullSupplier));
+        assertNull(cmd.getParsedOptionValue(optF, () -> null));
+
+        assertEquals("foo", cmd.getParsedOptionValue("f", "foo"));
+        assertEquals("foo", cmd.getParsedOptionValue("f", () -> "foo"));
+        assertNull(cmd.getParsedOptionValue("f", null));
+        assertNull(cmd.getParsedOptionValue("f", nullSupplier));
+        assertNull(cmd.getParsedOptionValue("f", () -> null));
+
+        assertEquals("foo", cmd.getParsedOptionValue('f', "foo"));
+        assertEquals("foo", cmd.getParsedOptionValue('f', () -> "foo"));
+        assertNull(cmd.getParsedOptionValue('f', null));
+        assertNull(cmd.getParsedOptionValue('f', nullSupplier));
+        assertNull(cmd.getParsedOptionValue('f', () -> null));
+
+    }
+
+    @Test
+    public void testNullOption() throws Exception {
         final Options options = new Options();
         final Option optI = Option.builder("i").hasArg().type(Number.class).build();
         final Option optF = Option.builder("f").hasArg().build();