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perf: Reduce exceptions of APIPage deserialization (#10548)
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perf: reduce exceptions of APIPage deserialization
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@filzrev
filzrev authored Feb 20, 2025
1 parent bbe254b commit b0f5472
Showing 1 changed file with 179 additions and 0 deletions.
179 changes: 179 additions & 0 deletions src/Docfx.Build/OneOfJsonConverterFactory.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,13 @@
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Diagnostics.Contracts;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text.Json;
using System.Text.Json.Serialization;
using Docfx.Build.ApiPage;
using OneOf;

#nullable enable
Expand Down Expand Up @@ -38,6 +42,9 @@ private class OneOfJsonConverter<T> : JsonConverter<T> where T : IOneOf
// It also depends on marking discriminator properties as required.
foreach (var (type, cast) in s_types)
{
if (!IsDeserializableType(ref reader, type, typeToConvert))
continue;

try
{
Utf8JsonReader readerCopy = reader;
Expand Down Expand Up @@ -77,5 +84,177 @@ private static (Type type, MethodInfo cast)[] GetOneOfTypes()
}
throw new InvalidOperationException($"{typeof(T)} isn't OneOf or OneOfBase");
}

/// <summary>
/// Helper method to check it can deserialize to specified type.
/// </summary>
/// <param name="reader">Current reader.</param>
/// <param name="type">The type that to be deserialized by JsonSerializer.</param>
/// <param name="typeToConvert">The type that to be converted by JsonConverter.</param>
private static bool IsDeserializableType(ref Utf8JsonReader reader, Type type, Type typeToConvert)
{
var tokenType = reader.TokenType;
switch (tokenType)
{
case JsonTokenType.String:
if (type == typeof(bool) && typeToConvert == typeof(OneOf<bool, string>))
return false;

Assert(type, [typeof(string), typeof(Span)]);
Assert(typeToConvert, [typeof(Span), typeof(Inline), typeof(OneOf<string, string[]>), typeof(OneOf<bool, string>)]);

return true;

case JsonTokenType.StartArray:
Assert(type, [typeof(string), typeof(string[]), typeof(Span), typeof(Span[])]);
Assert(typeToConvert, [typeof(Inline), typeof(OneOf<string, string[]>)]);

return type.IsArray;

case JsonTokenType.StartObject:
if (!TryGetFirstPropertyName(ref reader, out var propertyName))
return false;

var key = (typeToConvert, type, propertyName);

if (KnownTypes.Contains(key))
return true;

if (KnownTypesToSkip.Contains(key))
return false;

// Unknown type/name combinations found.
// Fallback to default behavior.
return true;

default:
return true;
}
}

private static bool TryGetFirstPropertyName(ref Utf8JsonReader reader, [NotNullWhen(true)] out string? propertyName)
{
Contract.Assert(reader.TokenType == JsonTokenType.StartObject);

var readerCopy = reader;
if (readerCopy.Read() && readerCopy.TokenType == JsonTokenType.PropertyName)
{
propertyName = readerCopy.GetString()!;
return true;
}

propertyName = null;
return false;
}

[Conditional("DEBUG")]
private static void Assert(
Type type,
Type[] expectedTypes,
[CallerArgumentExpression(nameof(expectedTypes))] string? message = null)
{
if (!expectedTypes.Contains(type))
throw new InvalidOperationException($"{type.Name} is not expected. Expected: {message}");
}

/// <summary>
/// Known type/name combinations that can be deserialize.
/// </summary>
private static readonly HashSet<(Type, Type, string)> KnownTypes =
[
// Block : OneOfBase<Heading, Api, Markdown, Facts, Parameters, List, Inheritance, Code>
(typeof(Block), typeof(Heading), "h1"),
(typeof(Block), typeof(Heading), "h2"),
(typeof(Block), typeof(Heading), "h3"),
(typeof(Block), typeof(Heading), "h4"),
(typeof(Block), typeof(Heading), "h5"),
(typeof(Block), typeof(Heading), "h6"),
(typeof(Block), typeof(Api), "api1"),
(typeof(Block), typeof(Api), "api2"),
(typeof(Block), typeof(Api), "api3"),
(typeof(Block), typeof(Api), "api4"),
(typeof(Block), typeof(Markdown), "markdown"),
(typeof(Block), typeof(Facts), "facts"),
(typeof(Block), typeof(Parameters), "parameters"),
(typeof(Block), typeof(List), "list"),
(typeof(Block), typeof(Inheritance), "inheritance"),
(typeof(Block), typeof(Code), "code"),

// Heading : OneOfBase<H1, H2, H3, H4, H5, H6>
(typeof(Heading), typeof(H1), "h1"),
(typeof(Heading), typeof(H2), "h2"),
(typeof(Heading), typeof(H3), "h3"),
(typeof(Heading), typeof(H4), "h4"),
(typeof(Heading), typeof(H5), "h5"),
(typeof(Heading), typeof(H6), "h6"),

// Api : OneOfBase<Api1, Api2, Api3, Api4>
(typeof(Api), typeof(Api1), "api1"),
(typeof(Api), typeof(Api2), "api2"),
(typeof(Api), typeof(Api3), "api3"),
(typeof(Api), typeof(Api4), "api4"),

// Span : OneOfBase<string, LinkSpan>
(typeof(Span), typeof(LinkSpan), "text"),

// Inline : OneOfBase<Span, Span[]>
(typeof(Inline), typeof(Span), "text"),
];

/// <summary>
/// Known type/name combinations that can not be deserialize.
/// </summary>
private static readonly HashSet<(Type, Type, string)> KnownTypesToSkip =
[
// Block : OneOfBase<Heading, Api, Markdown, Facts, Parameters, List, Inheritance, Code>
(typeof(Heading), typeof(H1), "h2"),
(typeof(Heading), typeof(H1), "h3"),
(typeof(Heading), typeof(H2), "h3"),
(typeof(Heading), typeof(H1), "h4"),
(typeof(Heading), typeof(H2), "h4"),
(typeof(Heading), typeof(H3), "h4"),
(typeof(Block), typeof(Heading), "api1"),
(typeof(Block), typeof(Heading), "api2"),
(typeof(Block), typeof(Heading), "api3"),
(typeof(Block), typeof(Heading), "api4"),
(typeof(Block), typeof(Heading), "markdown"),
(typeof(Block), typeof(Api), "markdown"),
(typeof(Block), typeof(Heading), "facts"),
(typeof(Block), typeof(Api), "facts"),
(typeof(Block), typeof(Markdown), "facts"),
(typeof(Block), typeof(Heading), "parameters"),
(typeof(Block), typeof(Api), "parameters"),
(typeof(Block), typeof(Markdown), "parameters"),
(typeof(Block), typeof(Facts), "parameters"),
(typeof(Block), typeof(Heading), "list"),
(typeof(Block), typeof(Api), "list"),
(typeof(Block), typeof(Markdown), "list"),
(typeof(Block), typeof(Facts), "list"),
(typeof(Block), typeof(Parameters), "list"),
(typeof(Block), typeof(Heading), "inheritance"),
(typeof(Block), typeof(Api), "inheritance"),
(typeof(Block), typeof(Markdown), "inheritance"),
(typeof(Block), typeof(Facts), "inheritance"),
(typeof(Block), typeof(Parameters), "inheritance"),
(typeof(Block), typeof(List), "inheritance"),
(typeof(Block), typeof(Heading), "code"),
(typeof(Block), typeof(Api), "code"),
(typeof(Block), typeof(Markdown), "code"),
(typeof(Block), typeof(Facts), "code"),
(typeof(Block), typeof(Parameters), "code"),
(typeof(Block), typeof(List), "code"),
(typeof(Block), typeof(Inheritance), "code"),

// OneOfBase<Api1, Api2, Api3, Api4>
(typeof(Api), typeof(Api1), "api2"),
(typeof(Api), typeof(Api1), "api3"),
(typeof(Api), typeof(Api2), "api3"),
(typeof(Api), typeof(Api1), "api4"),
(typeof(Api), typeof(Api2), "api4"),
(typeof(Api), typeof(Api3), "api4"),

// OneOfBase<string, LinkSpan>
(typeof(Span), typeof(String), "text"),
];
}
}

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