CJM v0.5.0 early-adopter feedback thread

[lmingzhi618]

CJM v0.5.0 is ready for early-adopter feedback.

CJM is a build-time metadata compiler for Modern C++. It reads ordinary C++ model declarations with Go-style JSON field metadata, builds a Metadata IR, and generates backend artifacts during the build.

Current outputs:

• ordinary nlohmann/json C++ integration
• opt-in JSON Schema Draft 2020-12 artifacts

This thread is for open-ended usage and adoption feedback:

• Would CJM fit any model-heavy C++ code you maintain?
• Does the FetchContent + cjm_generate workflow feel reasonable?
• Would generated JSON Schema artifacts help your downstream tooling?
• What parser limitations would block your real headers?
• Are the current diagnostics understandable?
• What type mappings are missing before v1.0?
• Does the generated code look readable enough to trust?
• Does the generated schema shape match what you would expect?

Useful links:

• Repo: https://github.com/cjm-labs/cxx-json-codegen
• v0.5.0 release: https://github.com/cjm-labs/cxx-json-codegen/releases/tag/v0.5.0
• v0.5.0 release notes: https://github.com/cjm-labs/cxx-json-codegen/blob/main/docs/releases/v0.5.0.md
• Dogfood report: https://github.com/cjm-labs/cxx-json-codegen/blob/main/docs/dogfood/ull-md-engine-v0.3.0.md

If you try CJM, please share the smallest practical model that worked or failed.