Merge pull request #617 from kdkavanagh/master

Warn instead of error on signed numInGrp, check for minValue < 0

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/xml/CompositeType.java

@@ -184,7 +184,18 @@ else if (!isUnsigned(blockLengthType.primitiveType()))
         }
         else if (!isUnsigned(numInGroupType.primitiveType()))
         {
-            XmlSchemaParser.handleError(node, "\"numInGroup\" must be unsigned type");
+            XmlSchemaParser.handleWarning(node, "\"numInGroup\" should be unsigned type");
+            final PrimitiveValue numInGroupMinValue = numInGroupType.minValue();
+            if (null == numInGroupMinValue)
+            {
+                XmlSchemaParser.handleError(node, "\"numInGroup\" minValue must be set for signed types");
+            }
+            else if (numInGroupMinValue.longValue() < 0)
+            {
+                XmlSchemaParser.handleError(node, String.format(
+                    "\"numInGroup\" minValue=%s must be greater than zero " +
+                    "for signed \"numInGroup\" types", numInGroupMinValue));
+            }
         }
         else
         {