import.meta.resolve with npm packages

[oscarotero]

Related: #16089

Every time I try to resolve a npm package:

const preact_specifier = import.meta.resolve("npm:preact");

I get the error:

Uncaught TypeError: "npm:" specifiers are currently not supported in import.meta.resolve()

I would rather the old behavior, returning simply npm:preact. This error is very unfortunated because now it's not possible to get the final specifier if the specifier is mapped in the import map:

{
  "imports": {
    "npm:preact": "https://esm.sh/preact"
  }
}

I guess this is the intended behavior would like to know the explanation for that decision.

[guybedford]

Strictly speaking, the specifier being loaded in the module registry is npm:preact in this case (and so far as it only has one representation in a given Deno application lifetime). So that this does sound like the sensible behaviour to me, while still treating the real cache location etc as an internal implementation detail.

[oscarotero]

To clarify, the sensible behavior to me is:

import.meta.resolve("npm:preact"); // Returns "npm:preact"

With this import map:

{
  "imports": {
    "npm:preact": "https://esm.sh/preact"
  }
}

import.meta.resolve("npm:preact"); // Returns "https://esm.sh/preact"

[lucacasonato]

I agree.

[bartlomieju]

Opened denoland/deno_core#354 that will make it easier to customize.