Self reference on array contents. Note the reference in the metadata may be wrong. This doesn't work yet, so the exact query hasn't been worked out yet.

find.json

{
    "objectType": "selfReferenceArrayContainsArray",
    "projection": [
        {
            "field": "*",
            "include": true,
            "recursive": true
        },{
            "field": "test_reference",
            "include": true,
            "recursive": true
        }
    ],
    "query": {
    	"field": "objectType",
    	"op": "=",
    	"rvalue": "selfReferenceArrayContainsArray"
    }
}

metadata.json

{
    "entityInfo": {
        "datastore": {
            "backend": "mongo",
            "collection": "selfReferenceArrayContainsArray",
            "datasource": "mongodata"
        },
        "defaultVersion": "0.0.1-SNAPSHOT",
        "name": "selfReferenceArrayContainsArray"
    },
    "schema": {
        "access": {
            "delete": [
                "anyone"
            ],
            "find": [
                "anyone"
            ],
            "insert": [
                "anyone"
            ],
            "update": [
                "anyone"
            ]
        },
        "fields": {
            "_id": {
                "type": "string",
                "constraints": {
                    "identity": true
                }
            },
            "a": {
                "type": "array",
                "items": {
                    "type": "string"
                }
            },
            "expectation": {
                "type": "string"
            },
            "test_reference": {
                "entity": "selfReferenceArrayContainsArray",
                "query": {
                    "$and": [
                        {
                            "field": "_id",
                            "op": "$neq",
                            "rfield": "$parent._id"
                        },
                        {
                            "field": "a",
                            "op": "$neq",
                            "rvalue": null
                        },
                        {
                            "$not": {
                                "array": "a",
                                "elemMatch": {
                                    "field": "$this",
                                    "op": "$nin",
                                    "rfield": "$parent.$parent.a"
                                }
                            }
                        }
                    ]
                },
                "type": "reference"
            }
        },
        "name": "selfReferenceArrayContainsArray",
        "status": {
            "value": "active"
        },
        "version": {
            "changelog": "selfReferenceArrayContainsArray",
            "value": "0.0.1-SNAPSHOT"
        }
    }
}

upsert-data.json

{
	"upsert": true,
	"data": [{
		"_id": "Q",
		"expectation": "test_reference {selfReferenceArrayContainsArray.a $in [a,b,c]} returns: S, T",
		"a": ["a","b","c"]
	},{
		"_id": "R",
		"expectation": "test_reference {selfReferenceArrayContainsArray.a $in [d,b,c]} returns: S, T",
		"a": ["d","b","c"]
	},{
		"_id": "S",
		"expectation": "test_reference {selfReferenceArrayContainsArray.a $in [b,c]} returns: T",
		"a": ["b","c"]
	},{
		"_id": "T",
		"expectation": "test_reference {selfReferenceArrayContainsArray.a $in [c]} returns: null",
		"a": ["c"]
	}]
}

The expectations don't match the query. array elemMatch query result will be true if the condition is true for at least one element of the array. Your expectations imply that you want it to be true for all array elements.

Use this instead: https://github.com/bserdar/lightblue-core/blob/ec8449d36d0335251cceb8d586cd2bff4cd53b7b/crud/src/test/resources/composite/self_ref_array_not_contains.json