hadashiA

hadashiA / NoJsonSchema

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Generate C# types and a zero-dependency UTF-8 JSON parser/emitter from JSON Schema.

10
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89% credibility
Found May 27, 2026 at 10 stars -- GitGems finds repos before they trend. Get early access to the next one.
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AI Analysis
C#
AI Summary

NoJsonSchema is a code generator for C# developers who work with JSON data following a published specification. You point it at a JSON Schema document (Draft 2020-12, Draft-07, or OpenAPI 3.x), and it generates C# types and UTF-8 JSON parsers/emitters that have zero runtime dependencies—just the basic .NET libraries. The generated code is optimized for speed and memory efficiency, making it suitable for high-performance applications, Native AOT compilation, Unity games using IL2CPP, and projects that need trimming-safe code. You can integrate it as a build-time source generator or use a standalone command-line tool.

How It Works

1
📋 You have a JSON specification to work with

You're building a C# project and need to work with data that follows a published JSON structure, like an API standard or industry specification.

2
🔍 You discover NoJsonSchema

You find a tool that can read your JSON specification and automatically create matching C# types, plus all the code needed to read and write JSON data.

3
⚡ Your code generates with zero extra libraries

The tool creates C# types and JSON handlers at build time. Everything the generated code needs is built into .NET itself - no third-party libraries to install or maintain.

4
Choose how you want to work
🔨
Source Generator (automatic)

Add the package to your project, point it at your schema files, and code appears when you build.

💻
Command-line tool

Run a simple command to generate C# files into a folder, useful for bulk generation or vendoring the output.

5
🎉 You get fast, efficient JSON handling

The generated code is optimized for speed and uses very little memory. It works in constrained environments where other approaches might struggle.

🚀 Your application comes to life

You write C# code using the generated types, call a simple Serialize or Deserialize method, and your app smoothly reads and writes JSON data that matches your specification.

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AI-Generated Review

What is NoJsonSchema?

NoJsonSchema is a build-time code generator for C# that takes a JSON Schema document and spits out strongly-typed POCOs alongside a hand-rolled UTF-8 JSON parser and serializer. Point it at a schema -- via CLI or source generator -- and you get one `.cs` file per type, a `Formatter` per type, and a namespace-wide `Serializer` entry point that the README describes as "Cache + Deserialize / Serialize." It supports Draft 2020-12, Draft-07, and OpenAPI 3.x schemas out of the box.

The killer feature? The generated code has zero runtime dependencies. No `System.Text.Json`, no `Newtonsoft.Json`, no reflection -- just the base class library. That makes it Native AOT-safe, Unity/IL2CPP-friendly, and trim-safe for publish-on-deploy scenarios.

Why is it gaining traction?

The performance numbers speak for themselves. Benchmarks on Apple M4 show 416ns for deserialize (1.36x faster than System.Text.Json source-gen) and 211ns for serialize with 64% fewer allocations on the deserialize path.

But the real hook is AOT compatibility. .NET developers working on Native AOT, Blazor WASM, or Unity games know that `System.Text.Json` source generators have rough edges with trimming and linking. NoJsonSchema sidesteps the entire problem -- the generated formatters are pure, stateless code with no reflection surface for the trimmer to complain about.

Who should use this?

- Backend devs consuming third-party JSON schemas who need a typed SDK where none officially exists - Protocol-bound developers using TypeSpec or schema-first workflows who need C# types aligned with their spec - Game and mobile developers targeting Unity/IL2CPP where runtime reflection is a liability - High-throughput services where the allocation and nanosecond differences actually matter at scale

Verdict

NoJsonSchema solves a real problem for a specific but substantial segment of .NET developers. The zero-dependency goal is genuinely novel compared to alternatives, and the AOT compatibility is what makes it值得 a look for constrained environments. That said, the 10-star count signals a young project -- the API surface, error handling for edge-case schema constructs, and community backing are all unproven. Approach it as a sharp tool for targeted use cases rather than a general-purpose fallback for `System.Text.Json`. MIT licensed.

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