Replace System.Text.Json dependency in AsmResolver.DotNet with internal light-weight JSON parser

[Washi1337]

Problem Description

The DotNet package uses System.Text.Json to interpret the runtimeconfig.json files associated to input binaries. System.Text.Json was introduced in .NET Core 3.0 or later, and we are currently targeting the latest LTS version of .NET 6.0. As a result, projects using AsmResolver.DotNet that target legacy .NET framework require pulling in many dependencies, including polyfill packages such as System.Buffers. For such a small (non-crucial) portion of the library, this seems excessive.

Proposal

Replace the System.Text.Json serializer/deserializer code with a small, lightweight JSON parser that we can embed into the library directly, effectively removing dependencies to System.Text.Json and other polyfill dependencies for consumers targeting legacy frameworks.

Alternatives

We can consider using compiler preprocessor directives to switch between implementations of the JSON parser (e.g., using a direcvtive like#if NETSTANDARD). This way, for builds targeting recent runtime versions, we can keep usingSystem.Text.Json and keep leveraging the simplicity and performance of this library, while for for older more generic builds, we use a light-weight JSON parser instead. The downside of this is that it requires maintaining two versions of the same functionality.

Additional Context

No response

[caesay]

I did this exact thing in my dotnet installer/auto-updater with preprocessor directives to use System.Text.Json on dotnet and Newtonsoft.Json on full framework. Feel free to steal it if it's helpful. https://github.com/velopack/velopack/blob/master/src/Velopack/Internal/SimpleJson.cs

[Washi1337]

Potential candidates for embeddable JSON parsers:

• https://github.com/Bunny83/SimpleJSON/blob/master/SimpleJSON.cs (MIT licensed)
• https://github.com/zanders3/json (MIT licensed)