Inconsistent results when mixing `fieldname: { fieldname: {` and `fieldname.fieldname` for mapping and indexing

[brwe]

The handling of objects in a mapping seems inconsistent. When adding fields with dots, for example afield.number, then, when indexing a document

"afield": {
    "number": 4
}

the type of "afield": { "number": is found correctly, but a second mapping for the object is added. This happens even if the indexing operation fails in case the type of "afield": { "number": does not correspond with "afield.number" as defined in the mapping.

An example is here: https://gist.github.com/brwe/11394327

There are two issue with this:

1. In STEP 2 (indexing the object) the indexing operation is rejected but the mapping for the object is still added. I do not think this should be so (This might be related to #5798)
2. It seems to me that when creating or merging mappings, it should be checked if pathes exist twice. For example, the following yields no error:

PUT /testindex/sometype/_mapping
{
   "sometype": {
      "properties": {
         "afield.number": {
            "type": "integer"
         },
         "afield.text": {
            "type": "string"
         },
         "afield": {
            "properties": {
               "number": {
                  "type": "string"
               }
            }
         }
      }
   }
}

[imotov]

It seems that during mapper lookup elasticsearch recognizes that fields with "." in them represent inner object fields, but during mapper creation it treats them as root level fields. Here is another example of this strange behavior that shows how elasticsearch treats such fields in case of dynamic mapping:

$ curl -XPUT localhost:9200/test/doc/1 -d '{"foo.bar": 10}'
{"_index":"test","_type":"doc","_id":"1","_version":1,"created":true}

$ curl -XPUT localhost:9200/test/doc/2 -d '{"foo": {"baz": "test"}}'
{"_index":"test","_type":"doc","_id":"2","_version":1,"created":true}

$ curl "localhost:9200/test/_mapping?pretty"
{
  "test" : {
    "mappings" : {
      "doc" : {
        "properties" : {
          "foo" : {
            "properties" : {
              "baz" : {
                "type" : "string"
              }
            }
          },
          "foo.bar" : {
            "type" : "long"
          }
        }
      }
    }
  }
}

[clintongormley]

Closing in favour of #6736