Added format attribute to @Parameter

src/main/java/org/scijava/command/CommandModuleItem.java

@@ -190,6 +190,11 @@ public Number getStepSize() {
 		}
 	}
 
+	@Override
+	public String getFormat() {
+		return getParameter().format();
+	}
+
 	@Override
 	public int getColumnCount() {
 		return getParameter().columns();

src/main/java/org/scijava/module/AbstractModuleItem.java

@@ -265,6 +265,11 @@ public Number getStepSize() {
 		return NumberUtils.toNumber("1", getType());
 	}
 
+	@Override
+	public String getFormat(){
+		return null;
+	}
+
 	@Override
 	public int getColumnCount() {
 		return 6;

src/main/java/org/scijava/module/ModuleItem.java

@@ -205,4 +205,6 @@ public interface ModuleItem<T> extends BasicDetails {
 	/** Sets the item's current value with respect to the given module. */
 	void setValue(Module module, T value);
 
+	/** Gets the item's format*/
+    String getFormat();
 }

src/main/java/org/scijava/plugin/Parameter.java

@@ -152,6 +152,9 @@
 	/** Defines the step size to use (numeric parameters only). */
 	String stepSize() default "";
 
+	/** Defines the format to use */
+	String format() default "";
+
 	/** Defines the list of possible values (multiple choice text fields only). */
 	String[] choices() default {};
 

src/main/java/org/scijava/widget/DefaultWidgetModel.java

@@ -262,6 +262,11 @@ public boolean isNumber() {
 		return Types.isNumber(getItem().getType());
 	}
 
+	@Override
+	public String getFormat() {
+		return item.getFormat();
+	}
+
 	@Override
 	public boolean isBoolean() {
 		return Types.isBoolean(getItem().getType());

src/main/java/org/scijava/widget/WidgetModel.java

@@ -175,6 +175,11 @@ public interface WidgetModel extends Contextual {
 	 */
 	boolean isNumber();
 
+	/**
+	 * Gets the format for the value of the model.
+	 */
+	String getFormat();
+
 	/**
 	 * Gets whether the input is a boolean type (i.e., {@link Boolean} or
 	 * {@code boolean}).

src/test/java/org/scijava/command/InvalidCommandTest.java

@@ -60,21 +60,6 @@ public void setUp() {
 		commandService = ctx.getService(CommandService.class);
 	}
 
-	@Test
-	public void testValid() {
-		final CommandInfo info = commandService.getCommand(ValidCommand.class);
-		assertNotNull(info);
-		assertTrue(info.isValid());
-
-		final List<ValidityProblem> problems = info.getProblems();
-		assertNotNull(problems);
-		assertEquals(0, problems.size());
-
-		final Number stepSize = info.getInput("x").getStepSize();
-		assertNotNull(stepSize);
-		assertEquals(10, stepSize.intValue());
-	}
-
 	@Test
 	public void testInvalid() {
 		final CommandInfo info = commandService.getCommand(InvalidCommand.class);

src/test/java/org/scijava/command/ValidNumberCommandTest.java

@@ -0,0 +1,101 @@
+/*
+ * #%L
+ * SciJava Common shared library for SciJava software.
+ * %%
+ * Copyright (C) 2009 - 2020 SciJava developers.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.command;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.scijava.Context;
+import org.scijava.ItemIO;
+import org.scijava.ValidityProblem;
+import org.scijava.plugin.Parameter;
+import org.scijava.plugin.Plugin;
+
+/**
+ * Test commands for verifying that invalid module parameters are dealt with
+ * using proper error handling.
+ * 
+ * @author Curtis Rueden
+ */
+public class ValidNumberCommandTest {
+
+	private CommandService commandService;
+
+	@Before
+	public void setUp() {
+		Context ctx = new Context(CommandService.class);
+		commandService = ctx.getService(CommandService.class);
+	}
+
+	@Test
+	public void testValid() {
+		final CommandInfo info = commandService.getCommand(ValidCommand.class);
+		assertNotNull(info);
+		assertTrue(info.isValid());
+
+		final List<ValidityProblem> problems = info.getProblems();
+		assertNotNull(problems);
+		assertEquals(0, problems.size());
+
+		final Number stepSize = info.getInput("x").getStepSize();
+		final String format = info.getInput("x").getFormat();
+		assertNotNull(stepSize);
+		assertEquals(10, stepSize.intValue());
+		assertEquals("0.000000", format);
+	}
+
+
+	// -- Helper classes --
+
+	/** A perfectly valid command! */
+	@Plugin(type = Command.class)
+	public static class ValidCommand implements Command {
+
+		@Parameter(stepSize = "10", format = "0.000000")
+		private double x;
+
+		@Parameter(type = ItemIO.OUTPUT)
+		private String validOutput;
+
+		@Override
+		public void run() {
+			validOutput = "ValidCommand: success!";
+		}
+
+	}
+
+
+}