This PR adds factory methods for the most common implementations:
* `SourceValueFetcher.identity` to pass through the source value untouched.
* `SourceValueFetcher.toString` to simply convert the source value to a string.
When constructing a value fetcher, the 'parsesArrayValue' flag must match
`FieldMapper#parsesArrayValue`. However there is nothing in code or tests to
help enforce this.
This PR reworks the value fetcher constructors so that `parsesArrayValue` is
'false' by default. Just as for `FieldMapper#parsesArrayValue`, field types must
explicitly set it to true and ensure the behavior is covered by tests.
Follow-up to #62974.
For runtime fields, we will want to do all search-time interaction with
a field definition via a MappedFieldType, rather than a FieldMapper, to
avoid interfering with the logic of document parsing. Currently, fetching
values for runtime scripts and for building top hits responses need to
call a method on FieldMapper. This commit moves this method to
MappedFieldType, incidentally simplifying the current call sites and freeing
us up to implement runtime fields as pure MappedFieldType objects.
This commit adds a mechanism to MapperTestCase that allows implementing
test classes to check that their parameters can be updated, or throw conflict
errors as advertised. Child classes override the registerParameters method
and tell the passed-in UpdateChecker class about their parameters. Simple
conflicts can be checked, using the existing minimal mappings as a base to
compare against, or alternatively a particular initial mapping can be provided
to check edge cases (eg, norms can be updated from true to false, but not
vice versa). Updates are registered with a predicate that checks that the update
has in fact been applied to the resulting FieldMapper.
Fixes#61631
To better align the plugin naming with other mapper plugins under x-pack (e.g.
mapper-flattened) this PR changes the plugin name and the containing directory
to "mapper-version"
Julie Tibshirani
Alan Woodward
Christoph Büscher