Mappings: Lock down _type field

see #8143
closes #9869

docs/reference/migration/migrate_2_0.asciidoc

@@ -242,6 +242,7 @@ Meta fields (those beginning with underscore) are fields used by elasticsearch
 to provide special features.  They now have limited configuration options.
 
 * `_id` configuration can no longer be changed.  If you need to sort, use `_uid` instead.
+* `_type` configuration can no longer be changed.
 
 === Codecs
 

src/main/java/org/elasticsearch/index/mapper/internal/TypeFieldMapper.java

@@ -30,6 +30,7 @@ import org.apache.lucene.search.Filter;
 import org.apache.lucene.search.PrefixFilter;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.Version;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.lucene.BytesRefs;
 import org.elasticsearch.common.lucene.Lucene;
@@ -94,6 +95,9 @@ public class TypeFieldMapper extends AbstractFieldMapper<String> implements Inte
     public static class TypeParser implements Mapper.TypeParser {
         @Override
         public Mapper.Builder parse(String name, Map<String, Object> node, ParserContext parserContext) throws MapperParsingException {
+            if (parserContext.indexVersionCreated().onOrAfter(Version.V_2_0_0)) {
+                throw new MapperParsingException(NAME + " is not configurable");
+            }
             TypeFieldMapper.Builder builder = type();
             parseField(builder, builder.name, node, parserContext);
             return builder;
@@ -187,6 +191,9 @@ public class TypeFieldMapper extends AbstractFieldMapper<String> implements Inte
 
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        if (writePre2xSettings == false) {
+            return builder;
+        }
         boolean includeDefaults = params.paramAsBoolean("include_defaults", false);
 
         // if all are defaults, no sense to write it at all

src/test/java/org/elasticsearch/count/query/CountQueryTests.java

@@ -227,7 +227,8 @@ public class CountQueryTests extends ElasticsearchIntegrationTest {
     }
 
     private void typeFilterTests(String index) throws Exception {
-        assertAcked(prepareCreate("test")
+        Settings indexSettings = ImmutableSettings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.V_1_4_2.id).build();
+        assertAcked(prepareCreate("test").setSettings(indexSettings)
                 .addMapping("type1", jsonBuilder().startObject().startObject("type1")
                         .startObject("_type").field("index", index).endObject()
                         .endObject().endObject())

src/test/java/org/elasticsearch/index/mapper/all/SimpleAllMapperTests.java

@@ -417,7 +417,6 @@ public class SimpleAllMapperTests extends ElasticsearchSingleNodeTest {
         rootTypes.put(SizeFieldMapper.NAME, "{\"enabled\" : true}");
         rootTypes.put(IndexFieldMapper.NAME, "{\"enabled\" : true}");
         rootTypes.put(SourceFieldMapper.NAME, "{\"enabled\" : true}");
-        rootTypes.put(TypeFieldMapper.NAME, "{\"store\" : true}");
         rootTypes.put("include_in_all", "true");
         rootTypes.put("dynamic_date_formats", "[\"yyyy-MM-dd\", \"dd-MM-yyyy\"]");
         rootTypes.put("numeric_detection", "true");

src/test/java/org/elasticsearch/index/mapper/simple/test-mapping.json

@@ -8,8 +8,6 @@
         enabled:true,
         _source:{
         },
-        _type:{
-        },
         _boost:{
             null_value:2.0
         },

src/test/java/org/elasticsearch/search/query/SearchQueryTests.java

@@ -597,7 +597,8 @@ public class SearchQueryTests extends ElasticsearchIntegrationTest {
     }
 
     private void typeFilterTests(String index) throws Exception {
-        assertAcked(prepareCreate("test")
+        Settings indexSettings = ImmutableSettings.builder().put(IndexMetaData.SETTING_VERSION_CREATED, Version.V_1_4_2.id).build();
+        assertAcked(prepareCreate("test").setSettings(indexSettings)
                 .addMapping("type1", jsonBuilder().startObject().startObject("type1")
                         .startObject("_type").field("index", index).endObject()
                         .endObject().endObject())

src/test/java/org/elasticsearch/search/suggest/ContextSuggestSearchTests.java

@@ -967,7 +967,6 @@ public class ContextSuggestSearchTests extends ElasticsearchIntegrationTest {
         XContentBuilder mapping = jsonBuilder();
         mapping.startObject();
         mapping.startObject(type);
-        mapping.startObject("_type").field("index", "not_analyzed").endObject(); // Forcefully configure the _type field, since it can be randomized and if used as context it needs to be enabled
         mapping.startObject("properties");
         mapping.startObject(FIELD);
         mapping.field("type", "completion");

src/test/java/org/elasticsearch/test/ElasticsearchIntegrationTest.java

@@ -312,11 +312,6 @@ public abstract class ElasticsearchIntegrationTest extends ElasticsearchTestCase
             XContentBuilder mappings = null;
             if (frequently() && randomDynamicTemplates()) {
                 mappings = XContentFactory.jsonBuilder().startObject().startObject("_default_");
-                if (randomBoolean()) {
-                    mappings.startObject(TypeFieldMapper.NAME)
-                            .field("index", randomFrom("no", "not_analyzed"))
-                            .endObject();
-                }
                 if (randomBoolean()) {
                     mappings.startObject(TimestampFieldMapper.NAME)
                             .field("enabled", randomBoolean())