fix(metaDataProduction): add class simple name as a tie-breaker when sorting producers - should make a more stable production of instance meta data (specifically, can make the JoinGraph more stable).

This is a potentially breaking change, in case anyone relied on the previous sort tie breaker (which was not specified by this class). To get the previous behavior, the system property qqq.MetaDataProducerHelper.disableNameTiebreaker can be set to true.

Author: darinkelkhoff

qqq-backend-core/src/main/java/com/kingsrook/qqq/backend/core/model/metadata/MetaDataProducerHelper.java

@@ -57,7 +57,16 @@
 
 
 /*******************************************************************************
- ** Help work with MetaDataProducers.
+ * Help work with MetaDataProducers.
+ *
+ * <p>Note that all of the public methods here use {@code sortMetaDataProducers},
+ * which by default will sort by the sortOrder specified in the producer objects,
+ * then by the type that they return, and finally by their class simple name.
+ * But - this sorting by class simple name was added in 0.40.0. Prior to that,
+ * there was no tie breaker on the sort.  To restore the previous behavior, set
+ * the system property {@code qqq.MetaDataProducerHelper.disableNameTiebreaker}
+ * to {@code true}.</p>
+ *
  *******************************************************************************/
 public class MetaDataProducerHelper
 {
@@ -69,7 +78,7 @@ public class MetaDataProducerHelper
    static
    {
       ////////////////////////////////////////////////////////////////////////////////////////
-      // define how we break ties in sort-order based on the meta-dta type.  e.g., do apps  //
+      // define how we break ties in sort-order based on the meta-data type.  e.g., do apps //
       // after all other types (as apps often try to get other types from the instance)     //
       // also - do backends earlier than others (e.g., tables may expect backends to exist) //
       // any types not in the map get the default value.                                    //
@@ -111,6 +120,7 @@ public static void processAllMetaDataProducersInPackage(QInstance instance, Stri
    }
 
 
+
    /***************************************************************************
     **
     ***************************************************************************/
@@ -190,11 +200,15 @@ public static List<MetaDataProducerInterface<?>> findProducers(String packageNam
 
 
    /***************************************************************************
-    **
+    * sort a list of producers: First by the sortOrder specified in the producer objects.
+    * Second based on their types, so kinds that depend on other kinds come later.
+    * Third, by class simple name, to give stable ordering (unless opt'ed out by system property).
+    * Note, we use simple name instead of name, in case, for some reason, you wanted to control
+    * the sort by naming your classes a certain way - easier to change Simple names than packages.
     ***************************************************************************/
    public static void sortMetaDataProducers(List<MetaDataProducerInterface<?>> producers)
    {
-      producers.sort(Comparator
+      Comparator<MetaDataProducerInterface<?>> comparator = Comparator
          .comparing((MetaDataProducerInterface<?> p) -> p.getSortOrder())
          .thenComparing((MetaDataProducerInterface<?> p) ->
          {
@@ -207,7 +221,26 @@ public static void sortMetaDataProducers(List<MetaDataProducerInterface<?>> prod
             {
                return (0);
             }
-         }));
+         });
+
+      //////////////////////////////////////////////////////////////////////////
+      // read this system property each time this method is called.           //
+      // normally we might read it once into a static var - but, e.g., tests  //
+      // might need to change the value over time.  and this isn't a hot code //
+      // path at all, so we can bear the cost each time we're called in here. //
+      //////////////////////////////////////////////////////////////////////////
+      String  propertyName          = "qqq.MetaDataProducerHelper.disableNameTiebreaker";
+      boolean disableNameTiebreaker = Boolean.getBoolean(propertyName);
+      if(disableNameTiebreaker)
+      {
+         LOG.warn("Name tiebreaker is disabled for MetaDataProducerHelper.sortMetaDataProducers.  This is legacy behavior, activated by system property [" + propertyName + "], which may be removed in a future release.");
+      }
+      else
+      {
+         comparator = comparator.thenComparing(p -> p.getClass().getSimpleName());
+      }
+
+      producers.sort(comparator);
    }
 
 
@@ -387,8 +420,8 @@ private static MetaDataProducerInterface<?> processChildRecordListWidget(Class<?
       String                         parentTableName  = getTableNameStaticFieldValue(sourceClass);
       String                         childTableName   = getTableNameStaticFieldValue(childEntityClass);
 
-      ChildRecordListWidget childRecordListWidget = childTable.childRecordListWidget();
-      ChildRecordListWidgetFromRecordEntityGenericMetaDataProducer producer = new ChildRecordListWidgetFromRecordEntityGenericMetaDataProducer(childTableName, parentTableName, childRecordListWidget);
+      ChildRecordListWidget                                        childRecordListWidget = childTable.childRecordListWidget();
+      ChildRecordListWidgetFromRecordEntityGenericMetaDataProducer producer              = new ChildRecordListWidgetFromRecordEntityGenericMetaDataProducer(childTableName, parentTableName, childRecordListWidget);
       producer.setSourceClass(sourceClass);
       return producer;
    }