Create analyzer accepting any random param and returning that in response as well

[amitmbm]

Elasticsearch Version

8.1.1

Installed Plugins

None

Java Version

bundled

OS Version

macos

Problem Description

Create a custom analyzer using below request, Note foo as an param to analyzer with bar value.

PUT customanlyzerindex
{
    "settings": {
        "analysis": {
            "analyzer": {
                "my_analyzer": {
                    "type": "custom",
                    "tokenizer": "standard",
                    "foo": "bar"
                }
            }
        }
    }
}

Index is created successfully, and foo param is returned in the _settings API response.

GET customanlyzerindex/_settings

{
    "customanz": {
        "settings": {
            "index": {
                "routing": {
                    "allocation": {
                        "include": {
                            "_tier_preference": "data_content"
                        }
                    }
                },
                "number_of_shards": "1",
                "provided_name": "customanz",
                "creation_date": "1649229792216",
                "analysis": {
                    "analyzer": {
                        "my_analyzer": {
                            "type": "custom",
                            "foo": "bar",
                            "tokenizer": "standard"
                        }
                    }
                },
                "number_of_replicas": "1",
                "uuid": "zo-99vRVQD6igTzbyFMNKA",
                "version": {
                    "created": "8010199"
                }
            }
        }
    }
}

Steps to Reproduce

Same as problem Description

Logs (if relevant)

N/A

[elasticmachine]

Pinging @elastic/es-search (Team:Search)

[amitmbm]

@martijnvg this is not related to highlighting, instead analysis. Hence correct tag should be ::Search/analysis

[ShailyTyagi]

I am interested in contributing - could somebody give me any useful pointers to be able to pick this issue up? I have gone through the readme(s)
@amitmbm

[javanna]

Hello @ShailyTyagi I believe https://github.com/elastic/elasticsearch/blob/master/server/src/main/java/org/elasticsearch/index/analysis/AnalysisRegistry.java is where we load the analyzers/normalizers/etc configured in the index settings. There we look at type and name but we seem to be silently ignoring any additional parameter, while we would like to instead throw exception whenever an unsupported parameter is provided.

[EverWinter23]

Hi @javanna @amitmbm , I found it interesting and was looking into it, and it seems like CustomAnalyzerProvider assigns the settings without validating. How should I proceed? I don't see any module being used to validate analyzer settings.

    public CustomAnalyzerProvider(IndexSettings indexSettings, String name, Settings settings) {
        super(indexSettings, name, settings);
        this.analyzerSettings = settings; // {"bar":"foo","foo":"bar","tokenizer":"standard","type":"custom"}
    }

[amitmbm]

@javanna would you be able to guide @EverWinter23 and @ShailyTyagi here, At first look it doesn't seems to be a small code change, but I might be completely wrong here.
Also would be more than happy to contribute here.