Chai v5 - Unknown file extension ".ts" when running with mocha v10

[matteobruni]

Hello,

I've already checked this without success. I'd prefer not using the solution suggested by the author of that discussion, also I didn't understand well how to achieve it, but since it doesn't seem the right way, I'd prefer using a cleaner solution.

I've tried also doing changes using this gist but when I run pnpm run test or mocha, mocha fails in an unexpected way, like the command is called without some arguments.

You can see my tests here: https://github.com/tsparticles/tsparticles/tree/v3/utils/tests (updated to v5 here https://github.com/tsparticles/tsparticles/tree/chai-v5/utils/tests)
And the failing error here: tsparticles/tsparticles#5277 in the failing GitHub Action

Can somebody help me fixing that?

For building the project (if needed):

First clone v3 branch, it's more updated than main

pnpm i
pnpm run slimbuild

once done this the first time, only utils/tests can be built using pnpm run build (it executes also the tests)

The chai dependency is in the root package.json config.

[43081j]

im gonna guess its this:
https://github.com/tsparticles/tsparticles/blob/69556009df1fa134c176da1f0eea83209fc2d3b8/utils/tests/.mocharc.json#L8

which you can see is different in the gist:
https://gist.github.com/43081j/78ce1392abb5043b02a29355006880a5#file-mocharc-json-L2

afaik you can specify both if somehow you have a mix of cjs/esm sources too (the require line and the loader line)

[matteobruni]

Additional info: adding only the loader didn't work, same error about registers, so I tried adding type module in the package.json and ES build in the tsconfig.json

[43081j]

this'll probably come down to the fact chai is esm only in 5.x

the gist uses type: "module" in its package.json. if you do the same in your repo, it'll be a breaking change keep in mind

if you stick to commonjs (by not having that type in your package.json), you'd have to use a dynamic import unfortunately (const chai = await import('chai');).

moving to ESM is no small task in most cases, so its fine to stay on chai 4.x for now (we're still doing security updates etc, feature set is the same roughly too)

if you want to move to ESM, you need:

• type: "module"
• tsconfig module: "nodenext" and moduleResolution: "nodenext"

[matteobruni]

I can migrate that test package to ESM without any issue, all the other packages are also exporting both ESM and CJS.

I've made both of these:

• type: "module"
• tsconfig module: "nodenext" and moduleResolution: "nodenext"

Also the tsconfig target is now ESNext

but that's where the last mocha command-like output comes out. Using nyc before mocha is not affecting anything, I've tried removing it but nothing changed.

I've noticed now that there were some non-existing folders referenced in the tsconfig (commit) but nothing changed again.

[43081j]

that sounds like mocha is struggling to find the test files

maybe try explicitly defining the glob, like here:
https://gist.github.com/43081j/78ce1392abb5043b02a29355006880a5#file-mocharc-json-L4-L6

[matteobruni]

Unfortunately it didn't work ☹️

[glektarssza]

Might help you. I've been fighting with this all evening and I finally got my version of things to work.

https://github.com/glektarssza/gh-action-setup-odin/tree/b9261bb6ab4c769b125e08b451a1c0d88b5b89f7

The general gist of what I had to do was:

• Create my own install-hooks.mjs file.
• Load that file in via the imports configuration option for Mocha.
• Change ALL my TypeScript extensions to .mts.
• Set the extension option for Mocha to include mts.
• Stop using TypeScript path aliases.

Given the massive headache this has been I'm probably going to look into a different assertion framework instead of Chai. It's just not worth it to throw an entire project into chaos because one package decided to move to ESM and only ESM.

[43081j]

i think you've come to the wrong conclusion there. you never had to update to 5.x. if you're not in an ESM project, you can happily stick to 4.x until the day you move to ESM (if ever).

in an ESM project, it should be very easy and natural to use chai and mocha without much change

[glektarssza]

Are there plans to continue supporting 4.x? e.g. back porting changes or security fixes from 5.x+ to 4.x? If not then there will, eventually, be a need to migrate to 5.x+.

Personally I try to keep my dependencies up to date with the latest available version. This is very much a personal preference and I understand that the pain I experienced is of my own doing since there was, strictly, no need to upgrade.

It's worth noting, though, that I've run into this even in a fresh ESM-style project because of TypeScript. ts-node does not fully support ESM yet, particularly the paths feature of TypeScript. They recommend using another package, tsconfig-paths, for this and that package does not support ESM at all. I think that's the ultimate root of my particular struggles.

[43081j]

Yes we are actively supporting 4.x. Many consumers are still on cjs projects so it wouldn't quite be fair to drop support

It is a shame ts-node has trouble with paths. Without paths, things do seem to work well in an esm project. Do you know if there's an issue in tsnode to solve that or a related discussion?

[glektarssza]

ts-node has the following ticket for their ESM loader: TypeStrong/ts-node#1514