Allow query_cluster: null in datastore config to hide types

[anthonycastiglia-toast]

Allow query_cluster: null in YAML Configuration

Issue

The hidden type spec acceptance tests specify that query_cluster: nil should hide index types from the GraphQL schema (hidden_types_spec.rb:21), and this works when modifying configs programatically as is done in the test:

config_index_def_of(query_cluster: nil) 

However, loading this configuration from YAML fails validation:

index_definitions:
  payments:
    query_cluster: null  # fails with Error: "value is not a string"

The JSON schema defines the query_cluster type as the non-nullable type: "string", even though accessible_from_queries? correctly handles nil at runtime.

Solution

Updated JSON schemas to accept ["string", "null"] and RBS signatures to ::String?. The field remains required to force explicit configuration choices.

Files changed:

• config_schema.yaml - Allow ['string', 'null']
• config.rb - Allow ["string", "null"]
• index_definition.rbs - Change to ::String?
• config_spec.rb - Add regression test

Testing

In addition to a new regression test for YAML validation with null, I've tested this locally by modifying the schema in config/settings/development.yaml:

     components: *main_index_settings
     electrical_parts: *main_index_settings
     manufacturers: *main_index_settings
-    mechanical_parts: *main_index_settings
+    mechanical_parts:
+      query_cluster: null
+      index_into_clusters: ["main"]
+      ignore_routing_values: []
+      custom_timestamp_ranges: []
+      setting_overrides:
+        number_of_shards: 1
+      setting_overrides_by_timestamp: {}
     teams: *main_index_settings
     widget_currencies: *main_index_settings
     widgets: *main_index_settings

Without the fix, starting elasticgraph locally via bundle exec boot_locally fails with

ElasticGraph::Errors::ConfigError: Invalid configuration for `ElasticGraph::DatastoreCore::Config` at `datastore`: Validation errors: (ElasticGraph::Errors::ConfigError)

{
  "data": null,
  "data_pointer": "/index_definitions/mechanical_parts/query_cluster",
  "schema_pointer": "/$defs/config/properties/index_definitions/patternProperties/.+/properties/query_cluster",
  "type": "string",
  "error": "value at `/index_definitions/mechanical_parts/query_cluster` is not a string"
}

After applying the fix, boot_locally succeeds and hides the mechanical_parts index as expected:

[CLAassistant]

All committers have signed the CLA.

[myronmarston]

LGTM apart from one suggested rewording.