feat: Nullable enabled

src/Directory.Build.props

@@ -24,5 +24,9 @@
   <PropertyGroup Condition="'$(MSBuildProjectName)' != 'Examine.Web.Demo' AND '$(MSBuildProjectName)' != 'Examine.Test'">
     <TargetFrameworks>net6.0;netstandard2.1;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
-
+
+  <!-- Disable the nullable warnings when compiling for .NET Standard 2.0 -->
+  <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <NoWarn>$(NoWarn);nullable</NoWarn>
+  </PropertyGroup>
 </Project>

src/Examine.Core/BaseIndexProvider.cs

@@ -39,7 +39,7 @@ protected BaseIndexProvider(ILoggerFactory loggerFactory, string name,
         /// <summary>
         /// A validator to validate a value set before it's indexed
         /// </summary>
-        public IValueSetValidator ValueSetValidator => _indexOptions.Validator;
+        public IValueSetValidator? ValueSetValidator => _indexOptions.Validator;
 
         /// <summary>
         /// Ensures that the node being indexed is of a correct type
@@ -113,13 +113,13 @@ public void DeleteFromIndex(IEnumerable<string> itemIds)
         #region Events
 
         /// <inheritdoc />
-        public event EventHandler<IndexOperationEventArgs> IndexOperationComplete;
+        public event EventHandler<IndexOperationEventArgs>? IndexOperationComplete;
 
         /// <inheritdoc />
-        public event EventHandler<IndexingErrorEventArgs> IndexingError;
+        public event EventHandler<IndexingErrorEventArgs>? IndexingError;
 
         /// <inheritdoc />
-        public event EventHandler<IndexingItemEventArgs> TransformingIndexValues;
+        public event EventHandler<IndexingItemEventArgs>? TransformingIndexValues;
 
         #endregion
 

src/Examine.Core/BaseSearchProvider.cs

@@ -22,10 +22,10 @@ protected BaseSearchProvider(string name)
         /// <param name="searchText"></param>
         /// <param name="maxResults"></param>
         /// <returns></returns>
-        public abstract ISearchResults Search(string searchText, QueryOptions options = null);
+        public abstract ISearchResults Search(string searchText, QueryOptions? options = null);
 
         /// <inheritdoc />
-		public abstract IQuery CreateQuery(string category = null, BooleanOperation defaultOperation = BooleanOperation.And);
+		public abstract IQuery CreateQuery(string? category = null, BooleanOperation defaultOperation = BooleanOperation.And);
 
     }
 }

src/Examine.Core/Examine.Core.csproj

@@ -5,6 +5,8 @@
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
     <Description>Examine is an abstraction for indexing and search operations with implementations such as Lucene.Net</Description>
     <PackageTags>examine search index</PackageTags>
+    <Nullable>enable</Nullable>
+    <LangVersion>9</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/Examine.Core/ExamineExtensions.cs

@@ -29,7 +29,7 @@ public static T GetNamedOptions<T>(this IOptionsMonitor<T> optionsMonitor, strin
         /// <returns></returns>
         public static IIndex GetIndex(this IExamineManager examineManager, string indexName)
         {
-            if (examineManager.TryGetIndex(indexName, out IIndex index))
+            if (examineManager.TryGetIndex(indexName, out IIndex? index))
             {
                 return index;
             }

src/Examine.Core/ExamineManager.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace Examine
@@ -27,11 +28,19 @@ public ExamineManager(IEnumerable<IIndex> indexes, IEnumerable<ISearcher> search
         private readonly ConcurrentDictionary<string, ISearcher> _searchers = new ConcurrentDictionary<string, ISearcher>(StringComparer.InvariantCultureIgnoreCase);
 
         /// <inheritdoc />
-        public bool TryGetSearcher(string searcherName, out ISearcher searcher) => 
+        public bool TryGetSearcher(string searcherName,
+#if !NETSTANDARD2_0
+            [MaybeNullWhen(false)]
+#endif
+            out ISearcher searcher) => 
             (searcher = _searchers.TryGetValue(searcherName, out var s) ? s : null) != null;
 
         /// <inheritdoc />
-        public bool TryGetIndex(string indexName, out IIndex index) => 
+        public bool TryGetIndex(string indexName,
+#if !NETSTANDARD2_0
+            [MaybeNullWhen(false)]
+#endif
+            out IIndex index) => 
             (index = _indexers.TryGetValue(indexName, out var i) ? i : null) != null;
 
         /// <inheritdoc />

src/Examine.Core/FieldDefinition.cs

@@ -32,7 +32,7 @@ public FieldDefinition(string name, string type)
 
         public bool Equals(FieldDefinition other) => string.Equals(Name, other.Name) && string.Equals(Type, other.Type);
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             return obj is FieldDefinition definition && Equals(definition);

src/Examine.Core/IExamineManager.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace Examine
@@ -29,7 +30,11 @@ public interface IExamineManager
         /// <param name="indexName"></param>
         /// <param name="index"></param>
         /// <returns>true if the index was found by name</returns>
-        bool TryGetIndex(string indexName, out IIndex index);
+        bool TryGetIndex(string indexName,
+#if !NETSTANDARD2_0
+            [MaybeNullWhen(false)]
+#endif
+            out IIndex index);
 
         /// <summary>
         /// Returns a searcher that was registered with <see cref="AddSearcher"/> or via config
@@ -39,7 +44,11 @@ public interface IExamineManager
         /// <returns>
         /// true if the searcher was found by name
         /// </returns>
-        bool TryGetSearcher(string searcherName, out ISearcher searcher);
+        bool TryGetSearcher(string searcherName,
+#if !NETSTANDARD2_0
+            [MaybeNullWhen(false)]
+#endif
+        out ISearcher searcher);
 
     }
 }

src/Examine.Core/ISearchResult.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 
 namespace Examine
 {
@@ -41,6 +41,6 @@ public interface ISearchResult
         /// </summary>
         /// <param name="key"></param>
         /// <returns></returns>
-        string this[string key] { get; }
+        string? this[string key] { get; }
     }
-}
+}

src/Examine.Core/ISearcher.cs

@@ -15,7 +15,7 @@ public interface ISearcher
         /// <param name="searchText">The search text or a native query</param>
         /// <param name="maxResults"></param>
         /// <returns>Search Results</returns>
-        ISearchResults Search(string searchText, QueryOptions options = null);
+        ISearchResults Search(string searchText, QueryOptions? options = null);
 
         /// <summary>
         /// Creates a search criteria instance as required by the implementation
@@ -25,6 +25,6 @@ public interface ISearcher
         /// <returns>
         /// An instance of <see cref="IQueryExecutor"/>
         /// </returns>
-        IQuery CreateQuery(string category = null, BooleanOperation defaultOperation = BooleanOperation.And);
+        IQuery CreateQuery(string? category = null, BooleanOperation defaultOperation = BooleanOperation.And);
     }
 }

src/Examine.Core/IndexOptions.cs

@@ -5,6 +5,6 @@ public class IndexOptions
         public IndexOptions() => FieldDefinitions = new FieldDefinitionCollection();
 
         public FieldDefinitionCollection FieldDefinitions { get; set; }
-        public IValueSetValidator Validator { get; set; }
+        public IValueSetValidator? Validator { get; set; }
     }
 }

src/Examine.Core/IndexingErrorEventArgs.cs

@@ -8,17 +8,17 @@ namespace Examine
     public class IndexingErrorEventArgs : EventArgs
     {
 
-        public IndexingErrorEventArgs(IIndex index, string message, string itemId, Exception exception)
+        public IndexingErrorEventArgs(IIndex index, string message, string? itemId, Exception? exception)
         {
             Index = index;
             ItemId = itemId;
             Message = message;
             Exception = exception;
         }
 
-        public Exception Exception { get; }
+        public Exception? Exception { get; }
         public string Message { get; }
         public IIndex Index { get; }
-        public string ItemId { get; }
+        public string? ItemId { get; }
     }
 }

src/Examine.Core/OrderedDictionary.cs

@@ -1,6 +1,7 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace Examine
@@ -10,7 +11,7 @@ namespace Examine
     /// </summary>
     /// <typeparam name="TKey"></typeparam>
     /// <typeparam name="TVal"></typeparam>
-    public class OrderedDictionary<TKey, TVal> : KeyedCollection<TKey, KeyValuePair<TKey, TVal>>, IDictionary<TKey, TVal>, IReadOnlyDictionary<TKey, TVal>
+    public class OrderedDictionary<TKey, TVal> : KeyedCollection<TKey, KeyValuePair<TKey, TVal>>, IDictionary<TKey, TVal>, IReadOnlyDictionary<TKey, TVal> where TKey : notnull
     {
         public OrderedDictionary()
         {
@@ -56,7 +57,14 @@ public void Add(TKey key, TVal value)
             base.Add(new KeyValuePair<TKey, TVal>(key, value));
         }
 
-        public bool TryGetValue(TKey key, out TVal value)
+#pragma warning disable CS8767 // Nullability of reference types in type of parameter doesn't match implicitly implemented member (possibly because of nullability attributes).
+        // Justification for warning disabled: IDictionary is missing [MaybeNullWhen(false)] in Netstandard 2.1
+        public bool TryGetValue(TKey key,
+#pragma warning restore CS8767 // Nullability of reference types in type of parameter doesn't match implicitly implemented member (possibly because of nullability attributes).
+#if !NETSTANDARD2_0
+            [MaybeNullWhen(false)]
+#endif
+            out TVal value)
         {
             if (base.Dictionary == null)
             {
@@ -89,7 +97,7 @@ TVal IDictionary<TKey, TVal>.this[TKey key]
                 {
                     return found.Value;
                 }
-                return default(TVal);
+                return default(TVal); // TODO: should this throw instead
             }
             set
             {
@@ -113,4 +121,4 @@ TVal IDictionary<TKey, TVal>.this[TKey key]
 
         public ICollection<TVal> Values => base.Dictionary != null ? base.Dictionary.Values.Select(x => x.Value).ToArray() : EmptyValues;
     }
-}
+}

src/Examine.Core/Search/FacetResult.cs

@@ -21,7 +21,7 @@ public IEnumerator<IFacetValue> GetEnumerator()
             return _values.GetEnumerator();
         }
 
-        public IFacetValue Facet(string label)
+        public IFacetValue? Facet(string label)
         {
             return _values.FirstOrDefault(field => field.Label.Equals(label));
         }

src/Examine.Core/Search/IFacetResult.cs

@@ -9,6 +9,6 @@ public interface IFacetResult : IEnumerable<IFacetValue>
         /// </summary>
         /// <param name="label"></param>
         /// <returns></returns>
-        IFacetValue Facet(string label);
+        IFacetValue? Facet(string label);
     }
 }

src/Examine.Core/Search/INestedQuery.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 
 namespace Examine.Search
 {
@@ -85,7 +85,7 @@ public interface INestedQuery
         /// <param name="query"></param>
         /// <param name="fields"></param>
         /// <returns></returns>
-        INestedBooleanOperation ManagedQuery(string query, string[] fields = null);
+        INestedBooleanOperation ManagedQuery(string query, string[]? fields = null);
 
         /// <summary>
         /// Matches items as defined by the IIndexFieldValueType used for the fields specified. 
@@ -100,4 +100,4 @@ public interface INestedQuery
         /// <returns></returns>
         INestedBooleanOperation RangeQuery<T>(string[] fields, T? min, T? max, bool minInclusive = true, bool maxInclusive = true) where T : struct;
     }
-}
+}

src/Examine.Core/Search/IQuery.cs

@@ -121,7 +121,7 @@ public interface IQuery
         /// <param name="query"></param>
         /// <param name="fields"></param>
         /// <returns></returns>
-        IBooleanOperation ManagedQuery(string query, string[] fields = null);
+        IBooleanOperation ManagedQuery(string query, string[]? fields = null);
 
         /// <summary>
         /// Matches items as defined by the IIndexFieldValueType used for the fields specified. 

src/Examine.Core/Search/IQueryExecutor.cs

@@ -9,6 +9,6 @@ public interface IQueryExecutor
         /// <summary>
         /// Executes the query
         /// </summary>
-        ISearchResults Execute(QueryOptions options = null);
+        ISearchResults Execute(QueryOptions? options = null);
     }
 }

src/Examine.Core/SearchResult.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Linq;
@@ -7,7 +7,7 @@ namespace Examine
 {
     public class SearchResult : ISearchResult
     {
-        private OrderedDictionary<string, string> _fields;
+        private OrderedDictionary<string, string>? _fields;
         private readonly Lazy<OrderedDictionary<string, IReadOnlyList<string>>> _fieldValues;
 
         /// <summary>
@@ -94,14 +94,14 @@ public IEnumerable<string> GetValues(string key)
         /// </summary>
         /// <param name="key"></param>
         /// <returns></returns>
-        public string this[string key] => Values.TryGetValue(key, out var single) ? single : null;
+        public string? this[string key] => Values.TryGetValue(key, out var single) ? single : null;
 
         /// <summary>
         /// Override this method so that the Distinct() operator works
         /// </summary>
         /// <param name="obj"></param>
         /// <returns></returns>
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (obj == null || GetType() != obj.GetType())
                 return false;