Expose tracing module to public API

[kwasimensah]

🔍 Search Terms

tracing API

✅ 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

Expose https://github.com/microsoft/TypeScript/blob/main/src/compiler/tracing.ts#L368 so that people using the compilerAPI can use the equivalent of --generateTrace to profile where typescript is spending it's time.

I wanted to see if this is something the Typescript team is interested in supporting. Happy to try and submit the PR myself if amenable to this.

📃 Motivating Example

When using the compiler API, we can't use the equivalent of --generateTrace to get in-depth information about where typescript is spending it's time

💻 Use Cases

1. What do you want to use this for?
   Using the compiler API programmatically with a custom CompilerHost that's trying to cache SourcefFiles between invocations (i.e. confirming some work I've been doing around Export SourceFileObject and friends  #57073)
2. What shortcomings exist with current approaches?
   Typescript already has an internal mechanism to collect these performance metrics and it would be great if programmatic access to this was allowed. In general it'd be great if we could do the equivalent of executeCommandLine with custom CompilerHost (including all the command line only options)
3. What workarounds are you using in the meantime?
   I can locally edit typescript to expose these functions

[DanielRosenwasser]

Personally, I think this is probably fine as long as we rename the API to something less generic than startTracing.

[jakebailey]

Yes, if we're going to export this, I definitely want to rework the API. It's sorta goofy right now.

[kwasimensah]

If there's work that you want done to the API that's more than a name change, then I'd bow out of trying to implement this myself because I can't promise to have the time for a lot of back and forths