assert that type handlers don't need object? - include test to valida…

…te (plus: NRT check was happy)

fix #1959

Dapper/PublicAPI.Shipped.txt

@@ -1,7 +1,7 @@
 #nullable enable
 abstract Dapper.SqlMapper.StringTypeHandler<T>.Format(T xml) -> string!
 abstract Dapper.SqlMapper.StringTypeHandler<T>.Parse(string! xml) -> T
-abstract Dapper.SqlMapper.TypeHandler<T>.Parse(object? value) -> T?
+abstract Dapper.SqlMapper.TypeHandler<T>.Parse(object! value) -> T?
 abstract Dapper.SqlMapper.TypeHandler<T>.SetValue(System.Data.IDbDataParameter! parameter, T? value) -> void
 const Dapper.DbString.DefaultLength = 4000 -> int
 Dapper.CommandDefinition
@@ -130,8 +130,8 @@ Dapper.SqlMapper.IParameterCallbacks.OnCompleted() -> void
 Dapper.SqlMapper.IParameterLookup
 Dapper.SqlMapper.IParameterLookup.this[string! name].get -> object?
 Dapper.SqlMapper.ITypeHandler
-Dapper.SqlMapper.ITypeHandler.Parse(System.Type! destinationType, object? value) -> object?
-Dapper.SqlMapper.ITypeHandler.SetValue(System.Data.IDbDataParameter! parameter, object? value) -> void
+Dapper.SqlMapper.ITypeHandler.Parse(System.Type! destinationType, object! value) -> object?
+Dapper.SqlMapper.ITypeHandler.SetValue(System.Data.IDbDataParameter! parameter, object! value) -> void
 Dapper.SqlMapper.ITypeMap
 Dapper.SqlMapper.ITypeMap.FindConstructor(string![]! names, System.Type![]! types) -> System.Reflection.ConstructorInfo?
 Dapper.SqlMapper.ITypeMap.FindExplicitConstructor() -> System.Reflection.ConstructorInfo?
@@ -149,7 +149,7 @@ override Dapper.DbString.ToString() -> string!
 override Dapper.SqlMapper.Identity.Equals(object? obj) -> bool
 override Dapper.SqlMapper.Identity.GetHashCode() -> int
 override Dapper.SqlMapper.Identity.ToString() -> string!
-override Dapper.SqlMapper.StringTypeHandler<T>.Parse(object? value) -> T
+override Dapper.SqlMapper.StringTypeHandler<T>.Parse(object! value) -> T
 override Dapper.SqlMapper.StringTypeHandler<T>.SetValue(System.Data.IDbDataParameter! parameter, T? value) -> void
 readonly Dapper.SqlMapper.Identity.commandType -> System.Data.CommandType?
 readonly Dapper.SqlMapper.Identity.connectionString -> string!

Dapper/SqlMapper.ITypeHandler.cs

@@ -15,15 +15,15 @@ public interface ITypeHandler
             /// </summary>
             /// <param name="parameter">The parameter to configure</param>
             /// <param name="value">Parameter value</param>
-            void SetValue(IDbDataParameter parameter, object? value);
+            void SetValue(IDbDataParameter parameter, object value);
 
             /// <summary>
             /// Parse a database value back to a typed value
             /// </summary>
             /// <param name="value">The value from the database</param>
             /// <param name="destinationType">The type to parse to</param>
             /// <returns>The typed value</returns>
-            object? Parse(Type destinationType, object? value);
+            object? Parse(Type destinationType, object value);
         }
     }
 }

Dapper/SqlMapper.TypeHandler.cs

@@ -23,9 +23,9 @@ public abstract class TypeHandler<T> : ITypeHandler
             /// </summary>
             /// <param name="value">The value from the database</param>
             /// <returns>The typed value</returns>
-            public abstract T? Parse(object? value);
+            public abstract T? Parse(object value);
 
-            void ITypeHandler.SetValue(IDbDataParameter parameter, object? value)
+            void ITypeHandler.SetValue(IDbDataParameter parameter, object value)
             {
                 if (value is DBNull)
                 {
@@ -37,7 +37,7 @@ void ITypeHandler.SetValue(IDbDataParameter parameter, object? value)
                 }
             }
 
-            object? ITypeHandler.Parse(Type destinationType, object? value)
+            object? ITypeHandler.Parse(Type destinationType, object value)
             {
                 return Parse(value);
             }
@@ -76,7 +76,7 @@ public override void SetValue(IDbDataParameter parameter, T? value)
             /// </summary>
             /// <param name="value">The value from the database</param>
             /// <returns>The typed value</returns>
-            public override T Parse(object? value)
+            public override T Parse(object value)
             {
                 if (value is null || value is DBNull) return default!;
                 return Parse((string)value);

tests/Dapper.Tests/DecimalTests.cs

@@ -20,7 +20,7 @@ public void Issue261_Decimals()
             parameters.Add("c", dbType: DbType.Decimal, direction: ParameterDirection.Output, precision: 10, scale: 5);
             connection.Execute("create proc #Issue261 @c decimal(10,5) OUTPUT as begin set @c=11.884 end");
             connection.Execute("#Issue261", parameters, commandType: CommandType.StoredProcedure);
-            var c = parameters.Get<Decimal>("c");
+            var c = parameters.Get<decimal>("c");
             Assert.Equal(11.884M, c);
         }
 

tests/Dapper.Tests/TypeHandlerTests.cs

@@ -374,7 +374,7 @@ private RatingValueHandler()
             {
             }
 
-            public static readonly RatingValueHandler Default = new RatingValueHandler();
+            public static readonly RatingValueHandler Default = new();
 
             public override RatingValue Parse(object? value)
             {
@@ -431,7 +431,7 @@ private StringListTypeHandler()
             {
             }
 
-            public static readonly StringListTypeHandler Default = new StringListTypeHandler();
+            public static readonly StringListTypeHandler Default = new();
             //Just a simple List<string> type handler implementation
             public override void SetValue(IDbDataParameter parameter, List<string>? value)
             {
@@ -739,5 +739,129 @@ public Issue461_ParameterisedTypeConstructor(int id, string someValue, Blarg som
             public string SomeValue { get; }
             public Blarg SomeBlargValue { get; }
         }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Issue1959_TypeHandlerNullability_Subclass(bool isNull)
+        {
+            Issue1959_Subclass_Handler.Register();
+            Issue1959_Subclass? when = isNull ? null : new(DateTime.Today);
+            var whenNotNull = when ?? new(new DateTime(1753, 1, 1));
+
+            var args = new HazIssue1959_Subclass { Id = 42, Nullable = when, NonNullable = whenNotNull };
+            var row = connection.QuerySingle<HazIssue1959_Subclass>(
+                "select @Id as [Id], @NonNullable as [NonNullable], @Nullable as [Nullable]",
+                args);
+
+            Assert.NotNull(row);
+            Assert.Equal(42, row.Id);
+            Assert.Equal(when, row.Nullable);
+            Assert.Equal(whenNotNull, row.NonNullable);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Issue1959_TypeHandlerNullability_Raw(bool isNull)
+        {
+            Issue1959_Raw_Handler.Register();
+            Issue1959_Raw? when = isNull ? null : new(DateTime.Today);
+            var whenNotNull = when ?? new(new DateTime(1753, 1, 1));
+
+            var args = new HazIssue1959_Raw { Id = 42, Nullable = when, NonNullable = whenNotNull };
+            var row = connection.QuerySingle<HazIssue1959_Raw>(
+                "select @Id as [Id], @NonNullable as [NonNullable], @Nullable as [Nullable]",
+                args);
+
+            Assert.NotNull(row);
+            Assert.Equal(42, row.Id);
+            Assert.Equal(when, row.Nullable);
+            Assert.Equal(whenNotNull, row.NonNullable);
+        }
+
+        public class HazIssue1959_Subclass
+        {
+            public int Id { get; set; }
+            public Issue1959_Subclass NonNullable { get; set; }
+            public Issue1959_Subclass? Nullable { get; set; }
+        }
+
+        public class HazIssue1959_Raw
+        {
+            public int Id { get; set; }
+            public Issue1959_Raw NonNullable { get; set; }
+            public Issue1959_Raw? Nullable { get; set; }
+        }
+
+        public class Issue1959_Subclass_Handler : SqlMapper.TypeHandler<Issue1959_Subclass>
+        {
+            public static void Register() => SqlMapper.AddTypeHandler<Issue1959_Subclass>(Instance);
+            private Issue1959_Subclass_Handler() { }
+            private static readonly Issue1959_Subclass_Handler Instance = new();
+            public override Issue1959_Subclass Parse(object? value)
+            {
+                Assert.NotNull(value);
+                Assert.IsType<DateTime>(value); // checking not DbNull etc
+                return new Issue1959_Subclass((DateTime)value);
+            }
+            public override void SetValue(IDbDataParameter parameter, TypeHandlerTests<TProvider>.Issue1959_Subclass value)
+                => parameter.Value = value.Value;
+        }
+
+        public class Issue1959_Raw_Handler : SqlMapper.ITypeHandler
+        {
+            public static void Register() => SqlMapper.AddTypeHandler(typeof(Issue1959_Raw), Instance);
+            private Issue1959_Raw_Handler() { }
+            private static readonly Issue1959_Raw_Handler Instance = new();
+
+            void SqlMapper.ITypeHandler.SetValue(IDbDataParameter parameter, object? value)
+            {
+                Assert.NotNull(value);
+                if (value is DBNull)
+                {
+                    parameter.Value = value;
+                }
+                else
+                {
+                    Assert.IsType<Issue1959_Raw>(value); // checking not DbNull etc
+                    parameter.Value = ((Issue1959_Raw)value).Value;
+                }
+            }
+            object? SqlMapper.ITypeHandler.Parse(Type destinationType, object? value)
+            {
+                Assert.NotNull(value);
+                Assert.IsType<DateTime>(value); // checking not DbNull etc
+                return new Issue1959_Raw((DateTime)value);
+            }
+        }
+
+#pragma warning disable CA2231 // Overload operator equals on overriding value type Equals
+        public readonly struct Issue1959_Subclass : IEquatable<Issue1959_Subclass>
+#pragma warning restore CA2231 // Overload operator equals on overriding value type Equals
+        {
+            public Issue1959_Subclass(DateTime value) => Value = value;
+            public readonly DateTime Value;
+            public override int GetHashCode() => Value.GetHashCode();
+            public override bool Equals(object? obj)
+                => obj is Issue1959_Subclass other && Equals(other);
+            public bool Equals(Issue1959_Subclass other)
+                => other.Value == Value;
+            public override string ToString() => Value.ToString();
+        }
+
+#pragma warning disable CA2231 // Overload operator equals on overriding value type Equals
+        public readonly struct Issue1959_Raw : IEquatable<Issue1959_Raw>
+#pragma warning restore CA2231 // Overload operator equals on overriding value type Equals
+        {
+            public Issue1959_Raw(DateTime value) => Value = value;
+            public readonly DateTime Value;
+            public override int GetHashCode() => Value.GetHashCode();
+            public override bool Equals(object? obj)
+                => obj is Issue1959_Raw other && Equals(other);
+            public bool Equals(Issue1959_Raw other)
+                => other.Value == Value;
+            public override string ToString() => Value.ToString();
+        }
     }
 }