Change error message to include field name and type

Author: mayya-sharipova

server/src/main/java/org/elasticsearch/search/collapse/CollapseBuilder.java

@@ -203,7 +203,8 @@ public CollapseContext build(QueryShardContext queryShardContext) {
             throw new IllegalArgumentException("no mapping found for `" + field + "` in order to collapse on");
         }
         if (fieldType.collapseType() == CollapseType.NONE) {
-            throw new IllegalArgumentException("collapse is not supported on this field type");
+            throw new IllegalArgumentException("collapse is not supported for the field [" + fieldType.name() +
+                "] of the type [" + fieldType.typeName() + "]");
         }
         if (fieldType.hasDocValues() == false) {
             throw new IllegalArgumentException("cannot collapse on field `" + field + "` without `doc_values`");

server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java

@@ -205,7 +205,7 @@ public void testBuildWithExceptions() {
             MappedFieldType fieldType = new MappedFieldType("field", true, false, true, TextSearchInfo.NONE, Collections.emptyMap()) {
                 @Override
                 public String typeName() {
-                    return null;
+                    return "some_type";
                 }
 
                 @Override
@@ -225,7 +225,7 @@ public Query existsQuery(QueryShardContext context) {
             when(shardContext.getFieldType("field")).thenReturn(fieldType);
             CollapseBuilder builder = new CollapseBuilder("field");
             IllegalArgumentException exc = expectThrows(IllegalArgumentException.class, () -> builder.build(shardContext));
-            assertEquals(exc.getMessage(), "collapse is not supported on this field type");
+            assertEquals(exc.getMessage(), "collapse is not supported for the field [field] of the type [some_type]");
         }
     }