import.meta.resolve doesn't work with npm specifiers.

[oscarotero]

The following code returns the same npm specifier instead of the url of the resolved file:

const reactLocation = import.meta.resolve("npm:react");

// npm:react

[bartlomieju]

I believe this is correct. If you do console.log(import.meta.resolve("https://deno.land/std@0.158.0/http/file_server.ts")); you will get "https://deno.land/std@0.158.0/http/file_server.ts", not the path to Deno cache.

[oscarotero]

@bartlomieju Is there any way to get the path of the cached file? I'm using it with esbuild to resolve and load dependencies for bundling.

[bartlomieju]

Not currently, no. You can do that, if you know the exact version you want to use though - deno info gives you information where a cache for npm packages resides and with that you can construct the path yourself.

It is something I also encountered when trying to write a plugin for rollup; so we will probably look into some more ergonomic way.

[deckchairlabs]

@oscarotero @bartlomieju Adding an import before the import.meta.resolve returns the path of the cached file.

import React from "npm:react";

console.log(import.meta.resolve("npm:react"));

[oscarotero]

This is a inconsistency and it doesn't work in all cases. This code returns an error

const specifier = "npm:react";
await import(specifier);

console.log(import.meta.resolve(specifier));
/* error: Uncaught (in promise) TypeError: Loading unprepared module: npm:react, imported from: file:///Users/oscarotero/www/test/deno/main.js */

For now, I'm using esm.sh to get the content of the npm packages: https://github.com/lumeland/lume/blob/6cca5823609ee3c036e7e51d918a304067bc9066/plugins/esbuild.ts#L82-L85

[guybedford]

Thinking in terms of a request URL / response URL may offer a little more flexibility here in in trying to reconcile any differences between import.meta.url and import.meta.resolve. Redirects allow the response URL (as import.meta.url represents) to be different to the request URL. import.meta.resolve then corresponds to the request URL as it is the client side resolver, before redirects are applied.

[oscarotero]

There's a casuistry that must be taken into account: the npm package that is not cached (because it wasn't imported previously). If it's decided that import.meta.resolve("npm:react") must return the cached file, but it isn't already cached, this means Deno must download and cache the package before return the filename.

[guybedford]

@oscarotero import.meta.resolve is synchronous uses the current resolver cache. This can be distinct from what the tracing loader is doing asynchronously. It is possible for import.meta.resolve to fail where dynamic import() would pass due to this distinction.

[bartlomieju]

Closed in #21716.