private CustomAnalyzer.Builder addTokenFilters(CustomAnalyzer.Builder builder,
                                                   LuceneAnalysisConfig.Analysis analysis) throws IOException {
        if (null == analysis) {
            // by default no token filters are added
            return builder;
        }
        for (LuceneAnalysisConfig.Analysis.TokenFilters tokenFilter : analysis.tokenFilters()) {
            builder.addTokenFilter(tokenFilter.name(), asModifiable(tokenFilter.conf()));
        }
        return builder;
    }
First, checks if a component is configured for a languageCode + StemMode.
Second, checks if Analyzer is configured only for a languageCode.
lucene-linguistics/src/main/java/com/yahoo/language/lucene/AnalyzerFactory.java