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Devirtualized default value comparison #37674

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merged 4 commits into from
Jun 22, 2020
Merged

Devirtualized default value comparison #37674

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1b5bc4a
Devirtualized default value comparison
YohDeadfall Jun 9, 2020
e295b48
Fixed double comparison for ref types
YohDeadfall Jun 14, 2020
12d5df9
Fixed serialization
YohDeadfall Jun 17, 2020
0cc6c0d
Addressed issues
YohDeadfall Jun 22, 2020
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3 changes: 0 additions & 3 deletions src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
Expand Down Expand Up @@ -76,8 +75,6 @@ internal override sealed JsonParameterInfo CreateJsonParameterInfo()
/// </summary>
internal bool IsInternalConverter { get; set; }

internal readonly EqualityComparer<T> _defaultComparer = EqualityComparer<T>.Default;

// This non-generic API is sealed as it just forwards to the generic version.
internal sealed override bool TryWriteAsObject(Utf8JsonWriter writer, object? value, JsonSerializerOptions options, ref WriteStack state)
{
Expand Down
65 changes: 31 additions & 34 deletions src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonPropertyInfoOfT.cs
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Expand Up @@ -2,9 +2,9 @@
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text.Json.Serialization;

namespace System.Text.Json
Expand All @@ -16,8 +16,6 @@ namespace System.Text.Json
/// or a type's converter, if the current instance is a <see cref="JsonClassInfo.PropertyInfoForClassInfo"/>.
internal sealed class JsonPropertyInfo<T> : JsonPropertyInfo
{
private static readonly T s_defaultValue = default!;
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Regardless of the rest of the change, there's definitely no need for this to exist.

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@steveharter steveharter Jun 10, 2020 •
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@layomia was this intended to actually contain a non-default value at some point in the future (when that feature is added)? e.g. System.String may want a default value of "" instead of null.

However, if\when we allow specifying a default value, we'd want an instance variable on this class (and\or on JsonClassInfo), not a static.

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was this intended to actually contain a non-default value at some point in the future (when that feature is added)?

Yup. No need to add it until we have that support - #36236.

we'd want an instance variable on this class (and\or on JsonClassInfo), not a static.

👍

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I see, but if this should be done for strings which is a ref type, then the comparer should be used in both branches, or they must be merged.


public Func<object, T>? Get { get; private set; }
public Action<object, T>? Set { get; private set; }

Expand Down Expand Up @@ -97,44 +95,45 @@ public override JsonConverter ConverterBase

public override bool GetMemberAndWriteJson(object obj, ref WriteStack state, Utf8JsonWriter writer)
{
bool success;
T value = Get!(obj);

// Since devirtualization only works in non-shared generics,
// the default comparer is uded only for value types for now.
// For reference types there is a quick check for null.
if (IgnoreDefaultValuesOnWrite && (
default(T) == null ? value == null : EqualityComparer<T>.Default.Equals(default, value)))
{
return true;
}

if (value == null)
{
Debug.Assert(s_defaultValue == null && Converter.CanBeNull);
Debug.Assert(Converter.CanBeNull);

success = true;
if (!IgnoreDefaultValuesOnWrite)
if (Converter.HandleNull)
{
if (!Converter.HandleNull)
// No object, collection, or re-entrancy converter handles null.
Debug.Assert(Converter.ClassType == ClassType.Value);

if (state.Current.PropertyState < StackFramePropertyState.Name)
{
writer.WriteNullSection(EscapedNameSection);
state.Current.PropertyState = StackFramePropertyState.Name;
writer.WritePropertyNameSection(EscapedNameSection);
}
else

int originalDepth = writer.CurrentDepth;
Converter.Write(writer, value, Options);
if (originalDepth != writer.CurrentDepth)
{
// No object, collection, or re-entrancy converter handles null.
Debug.Assert(Converter.ClassType == ClassType.Value);

if (state.Current.PropertyState < StackFramePropertyState.Name)
{
state.Current.PropertyState = StackFramePropertyState.Name;
writer.WritePropertyNameSection(EscapedNameSection);
}

int originalDepth = writer.CurrentDepth;
Converter.Write(writer, value, Options);
if (originalDepth != writer.CurrentDepth)
{
ThrowHelper.ThrowJsonException_SerializationConverterWrite(Converter);
}
ThrowHelper.ThrowJsonException_SerializationConverterWrite(Converter);
}
}
}
else if (IgnoreDefaultValuesOnWrite && Converter._defaultComparer.Equals(s_defaultValue, value))
{
Debug.Assert(s_defaultValue != null && !Converter.CanBeNull);
success = true;
else
{
writer.WriteNullSection(EscapedNameSection);
}

return true;
}
else
{
Expand All @@ -144,10 +143,8 @@ public override bool GetMemberAndWriteJson(object obj, ref WriteStack state, Utf
writer.WritePropertyNameSection(EscapedNameSection);
}

success = Converter.TryWrite(writer, value, Options, ref state);
return Converter.TryWrite(writer, value, Options, ref state);
}

return success;
}

public override bool GetMemberAndWriteJsonExtensionData(object obj, ref WriteStack state, Utf8JsonWriter writer)
Expand Down Expand Up @@ -179,7 +176,7 @@ public override bool ReadJsonAndSetMember(object obj, ref ReadStack state, ref U
ThrowHelper.ThrowJsonException_DeserializeUnableToConvertValue(Converter.TypeToConvert);
}

Debug.Assert(s_defaultValue == null);
Debug.Assert(default(T) == null);

if (!IgnoreDefaultValuesOnRead)
{
Expand Down