ModuleService: add getDefaultValue(ModuleItem)

This logic goes into the ModuleService because it needs context:
when the item does not specify a min or max value, it leans on the
ConvertService to convert from zero (specifically: "0") to the
ModuleItem's associated type.

Author: ctrueden

pom.xml

@@ -10,7 +10,7 @@
 	</parent>
 
 	<artifactId>scijava-common</artifactId>
-	<version>2.40.1-SNAPSHOT</version>
+	<version>2.41.0-SNAPSHOT</version>
 
 	<name>SciJava Common</name>
 	<description>SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by both ImageJ and SCIFIO.</description>

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

@@ -300,6 +300,22 @@ public <T> T load(final ModuleItem<T> item) {
 		return convertService.convert(sValue, item.getType());
 	}
 
+	@Override
+	public <T> T getDefaultValue(final ModuleItem<T> item) {
+		final T min = item.getMinimumValue();
+		if (min != null) return min;
+		final T softMin = item.getSoftMinimum();
+		if (softMin != null) return softMin;
+		final T max = item.getMaximumValue();
+		if (max != null) return max;
+		final T softMax = item.getSoftMaximum();
+		if (softMax != null) return softMax;
+		final T zero = convertService.convert("0", item.getType());
+		if (zero != null) return zero;
+		// no known default value
+		return null;
+	}
+
 	// -- Service methods --
 
 	@Override

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

@@ -285,4 +285,8 @@ <M extends Module> Future<M> run(M module,
 	 * {@link ModuleItem}.
 	 */
 	<T> T load(ModuleItem<T> item);
+
+	/** Gets the default value of the given {@link ModuleItem}. */
+	<T> T getDefaultValue(final ModuleItem<T> item);
+
 }