ExtSchemaPopulateHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
using Sitecore.ContentSearch.SolrProvider.Pipelines.PopulateSolrSchema;
using SolrNet.Schema;

public class ExtSchemaPopulateHelper : SchemaPopulateHelper
{
  private readonly SolrSchema schema;

  public ExtSchemaPopulateHelper(SolrSchema solrSchema) : base(solrSchema) => this.schema = solrSchema;

  public override IEnumerable<XElement> GetAllFieldTypes() => this.GetReplaceFields().Union(this.GetAddFieldTypes()).Where(o => o != null);

  private IEnumerable<XElement> GetAddFieldTypes()
  {
    var schemaPopulateHelper = this;
    yield return schemaPopulateHelper.CreateFieldType("random", "solr.RandomSortField", new Dictionary<string, string>()
    {
      {
        "indexed",
        "true"
      }
    });
    yield return schemaPopulateHelper.CreateFieldType("ignored", "solr.StrField", new Dictionary<string, string>()
    {
      {
        "indexed",
        "false"
      },
      {
        "stored",
        "false"
      },
      {
        "docValues",
        "false"
      },
      {
        "multiValued",
        "true"
      }
    });
  }

  private XElement CreateFieldType(string name, string @class, IDictionary<string, string> properties)
  {
    var xelement = new XElement(this.TypeExists(name) ? "replace-field-type" : "add-field-type");
    xelement.Add(new XElement(nameof(name), name));
    xelement.Add(new XElement(nameof(@class), @class));
    foreach (var property in properties)
    {
      xelement.Add(new XElement(property.Key, property.Value));
    }

    return xelement;
  }

  private XElement GetReplaceTextGeneralFieldType()
  {
    SolrFieldType solrFieldType = this.schema.SolrFieldTypes.Find((Predicate<SolrFieldType>)(f => f.Name == "text_general"));
    
    if (solrFieldType == null)
    {
      return (XElement)null;
    }
    
    XElement generalFieldType = new XElement((XName)"replace-field-type");
    
    generalFieldType.Add(new XElement((XName)"name", solrFieldType.Name));
    generalFieldType.Add(new XElement((XName)"class", solrFieldType.Type));
    generalFieldType.Add(new XElement((XName)"positionIncrementGap", "100"));
    generalFieldType.Add(new XElement((XName)"multiValued", "false"));

    XElement content1 = new XElement((XName)"indexAnalyzer");
    
    content1.Add(new XElement((XName)"tokenizer", new XElement((XName)"class", "solr.StandardTokenizerFactory")));
    content1.Add(new XElement((XName)"filters", new object[3]
    {
       new XElement((XName) "class",  "solr.StopFilterFactory"),
       new XElement((XName) "ignoreCase",  "true"),
       new XElement((XName) "words",  "stopwords.txt")
    }));
    
    content1.Add(new XElement((XName)"filters", new XElement((XName)"class", "solr.LowerCaseFilterFactory")));

    content1.Add(new XElement((XName)"filters", new object[2]
    {
       new XElement((XName) "class",  "solr.ASCIIFoldingFilterFactory"),
       new XElement((XName) "preserveOriginal",  "true"),
    }));

    content1.Add(new XElement((XName)"charFilters", new object[2]
    {
       new XElement((XName) "class",  "solr.MappingCharFilterFactory"),
       new XElement((XName) "mapping",  "mapping-FoldToASCII.txt"),
    }));
    
    content1.Add(new XElement((XName)"charFilters", new object[2]
    {
       new XElement((XName) "class",  "solr.MappingCharFilterFactory"),
       new XElement((XName) "mapping",  "mapping-FoldToASCII.txt"),
    }));

    generalFieldType.Add(content1);

    XElement content2 = new XElement((XName)"queryAnalyzer");
    
    content2.Add(new XElement((XName)"tokenizer", new XElement((XName)"class", "solr.StandardTokenizerFactory")));
    content2.Add(new XElement((XName)"filters", new object[3]
    {
       new XElement((XName) "class",  "solr.StopFilterFactory"),
       new XElement((XName) "ignoreCase",  "true"),
       new XElement((XName) "words",  "stopwords.txt")
    }));
    
    content2.Add(new XElement((XName)"filters", new object[4]
    {
       new XElement((XName) "class",  "solr.SynonymFilterFactory"),
       new XElement((XName) "synonyms",  "synonyms.txt"),
       new XElement((XName) "ignoreCase",  "true"),
       new XElement((XName) "expand",  "true")
    }));
    
    content2.Add(new XElement((XName)"filters", new XElement((XName)"class", "solr.LowerCaseFilterFactory")));
    
    generalFieldType.Add(content2);
    
    return generalFieldType;
  }

  private IEnumerable<XElement> GetReplaceFields()
  {
    yield return this.GetReplaceTextGeneralFieldType();
  }
}