npm: import require of tslib fails, import_map does not help

[tv42]

npm package using require to get hold of tslib fails, making using that package impossible (without CDN hacks).

@kitsonk at #5427 (comment) thinks that using an import_map would help, but it doesn't:

podman run -it --rm --user deno docker.io/denoland/deno:alpine /bin/sh
/ $ deno --version
deno 1.32.1 (release, x86_64-unknown-linux-gnu)
v8 11.2.214.9
typescript 5.0.2
/ $ cat >/tmp/import_map.json <<EOF
{
  "imports": {
    "tslib": "npm:tslib@2.5.0",
    "ts-results": "npm:ts-results@3.3.0"
  }
}
EOF
/ $ deno eval --import-map /tmp/import_map.json 'import { Err, Ok, Result } from "ts-results";'
error: Uncaught Error: Cannot find module 'tslib'
Require stack:
- /deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js
- /deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js
    at Function.Module._resolveFilename (ext:deno_node/01_require.js:825:15)
    at Function.Module._load (ext:deno_node/01_require.js:657:27)
    at Module.require (ext:deno_node/01_require.js:871:19)
    at require (ext:deno_node/01_require.js:1011:16)
    at file:///deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js:12:19
    at file:///deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js:3:17
    at Object.<anonymous> (file:///deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js:9:3)
    at Object.<anonymous> (file:///deno-dir/npm/registry.npmjs.org/ts-results/3.3.0/index.js:17:4)
    at Module._compile (ext:deno_node/01_require.js:938:34)
    at Object.Module._extensions..js (ext:deno_node/01_require.js:971:10)
/ $

Related issues: #5427 #17403 #17841 denoland/manual#147

[marvinhagemeister]

Had a quick peek at this and the issue is that the module isn't fetched at all. It's nowhere to be found on disk. The resolution logic itself seems to be correct and searches in all the right places.

[bartlomieju]

@marvinhagemeister that's a good pointer - my hunch is that ts-results specifies tslib dependency in some strange way that we haven't considered and our logic doesn't pick it up as an npm package that should be fetched. I would suggest to look into ts-results and see how tslib is loaded in there, since it's a CommonJS file our static analysis might not handle that case correctly.

[bartlomieju]

The CJS analysis can be found in https://github.com/denoland/deno_ast/blob/main/src/cjs_parse.rs

[tv42]

Maybe this can help explain what ts-results is doing in a non-typical way: vultix/ts-results#37

[dsherret]

The issue is that ts-results does not specify tslib is a peer dependency and yet it attempts to import it in its index.js file.

You can work around this by telling deno to load the tslib package from the import map as well:

 deno eval --import-map /tmp/import_map.json 'import "tslib"; import { Err, Ok, Result } from "ts-results";'

(Note that an import map is not a dependency manifest file, but rather a way to map specifiers, so you need an explicit side import to get it to be resolved and load)

[lucacasonato]

I will close this because this is very obviously a ts-results bug, see vultix/ts-results#38.