New command API and runtime JSON Schema (and TypeScript) code generation

[tamasfe]

I had a tool lying around that I once wrote for a project where we generated typescript code from JSON schema files, but it wasn't used anymore. Fortunately it was written in Rust, so I thought I'd strip the unneeded features and repurpose it for code generation in Tauri.

In the process I also wrote a command API that is similar to how actix-web creates its route handlers, which means that command handlers don't require macros as they are ordinary functions or closures.

A command macro on functions can still be used to provide additional metadata, currently documentation from doc comments, and argument names, but it's not required for type-safe code generation.

The TS code is generated at runtime, this way the generated code is always up-to-date and there is no fiddling with build scripts or macros as rustc does most of the work.

My work pretty much touched on these issues:

• [refactor] replace command macro #3256
• [feat] Generate Typescript Declaration from Structs in Rust #3586
• Feature: Generate Typescript functions for Rust commands #1514

It's not yet documented, but it is only ~1k loc so I believe the provided example should be enough to get an idea.

I didn't want to open a PR yet as I did not need anything from the Tauri internals and wanted to avoid the overhead of integration. I can follow-up with a PR (or anyone else for that matter) if it's desirable.

The code is available here:

https://github.com/tamasfe/tauri-commands