improve deprecation warnings for invalid match_mapping_type values

Author: javanna

core/src/main/java/org/elasticsearch/index/mapper/DynamicTemplate.java

@@ -155,7 +155,7 @@ public static XContentFieldType fromString(String value) {
                     return v;
                 }
             }
-            throw new IllegalArgumentException("No xcontent type matched on [" + value + "], possible values are "
+            throw new IllegalArgumentException("No field type matched on [" + value + "], possible values are "
                     + Arrays.toString(values()));
         }
 
@@ -208,12 +208,8 @@ public static DynamicTemplate parse(String name, Map<String, Object> conf,
             try {
                 xcontentFieldType = XContentFieldType.fromString(matchMappingType);
             } catch (IllegalArgumentException e) {
-                // TODO: do this in 6.0
-                /*if (indexVersionCreated.onOrAfter(Version.V_6_0_0)) {
-                    throw e;
-                }*/
-
-                DEPRECATION_LOGGER.deprecated("Ignoring unrecognized match_mapping_type: [" + matchMappingType + "]");
+                DEPRECATION_LOGGER.deprecated("match_mapping_type [" + matchMappingType + "] is invalid and will be ignored: "
+                        + e.getMessage());
                 // this template is on an unknown type so it will never match anything
                 // null indicates that the template should be ignored
                 return null;

core/src/test/java/org/elasticsearch/index/mapper/DynamicTemplateTests.java

@@ -56,8 +56,8 @@ public void testParseUnknownMatchType() throws IOException {
         templateDef.put("mapping", Collections.singletonMap("store", true));
         // if a wrong match type is specified, we ignore the template
         assertNull(DynamicTemplate.parse("my_template", templateDef, Version.V_5_0_0_alpha5));
-        //TODO clarify this deprecation warning
-        assertWarnings("Ignoring unrecognized match_mapping_type: [short]");
+        assertWarnings("match_mapping_type [short] is invalid and will be ignored: No field type matched on [short], " +
+                "possible values are [object, string, long, double, boolean, date, binary]");
     }
 
     public void testMatchAllTemplate() {