npm: automatic acquisition of `@types` package for type checking

[nayeemrmn]

This was already on the roadmap but with no issue.

You can usually work around this with // @deno-types="npm:@types/<package>" but that's not always an option. E.g. for "jsxImportSource": "npm:react" in your compiler options, there's no import to add the directive to. So it's a big obstacle for react-jsx users.

[dsherret]

I don't think we should do this.

1. It's magical—the types package version isn't specified.
2. It's extremely common for the version of a @types/<package-name> package to not align with the actual package version.
3. Figuring out if we need to do automatic type acquisition will make npm resolution slower as we need to analyze the package for if it has types (which can only be done once the tarball has been downloaded and extracted), check if there's a @types/<package-name> for that version or approxiamte version (which could be wrong), and then finally fill in that association to deno_graph (or alternatively we could require downloading and extracting all top level packages before we complete the initial deno_graph resolution).

[KyleJune]

Not being able to use npm specifiers for jsxImportSource makes using react pretty painful in Deno. Anyone that wants to use it basically has to use esm.sh still because of this issue. See #18203 for an example.

The current hack to get react types is pretty ugly and not obvious, the only reason I know about it is from finding that issue linked above. I don't have this problem with esm.sh and thought the point of npm specifiers was so that we wouldn't need esm.sh.

// See: https://github.com/denoland/deno/issues/16653
import type {} from "npm:@types/react@18";
import type {} from "npm:@types/react-dom@18";

The other option of adding a comment is a bit painful too. I don't think you need to do anything like that to get types for your npm dependencies in node.

// @deno-types="npm:@types/<package>"

It would be great if we could just import react and get the types we would expect to get if we did the same in node.

[dsherret]

@KyleJune I think we need a different solution for that then this. For example, this won't help if there is a version mismatch. Let's discuss in the other issue.

[oscarotero]

I think the main problem is not if the option is ugly or not, but there's no way to specify this globally. Maybe an option in deno.json to assign types to any module? Something like:

{
  "compilerOptions": {
    "jsx": "react-jsx",
    "jsxImportSource": "npm:react",
  }, 
  "types": {
    "npm:react": "npm:@types/react@18"
  }
}

[dsherret]

@oscarotero yes, see #18203 (comment) and below

[sant123]

@dsherret should this work for any package right? I'm testing with mssql but I still need to specify the @deno-types comment.

With comment:

Without comment:

[dsherret]

Sorry, this issue shouldn't have been closed as part of jsxImportSourceTypes support. That said, I'm pretty sure this issue won't ever be done for the reasons I outlined above and so I'm going to close this as not planned.