Cache Declarations Directory

🔍 Search Terms

cache declarations cached tsserver tsc

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

A cache directory for declaration files that can be used both for normal type declaration and for tsserver.

This would be a shared folder to use for type definitions in development and possibly for build steps.

A separate folder could mean you have one service that could have it's own optimizations running in parallel or for some part of the project and emitting the declaration files, while the rest is worked normally or even tsserver rely only those declarations.

📃 Motivating Example

https://github.com/trpc/trpc/discussions/2448#discussioncomment-11151754

💻 Use Cases

With tools that relies heavily on TS, some projects see inference times of seconds and have to rely on splitting code into a monorepo or some indirect compilation step and then depending on those types.

1. What do you want to use this for?

Faster inference in large projects with tooling with complex, nested types.

2. What shortcomings exist with current approaches?

Some relies on splitting code into a monorepo, others you need multiple tsconfigs so you can generate the types in one place and then reference them in the actual code, making indirections on the type system to keep the inference speed.

3. What workarounds are you using in the meantime?

Have a parallel config to generate types and change a critical entrypoint to use the generated types instead of the normally inferred one.

Start by reviewing the suggestion, use cases, and linked trpc discussion to clarify the required declaration-cache behavior. Done would require a defined shared cache directory that supports normal declaration use, tsserver, and possibly build steps, with the scope and integration points specified.