`.cjs` extension is supported, but not `.cts` in version 2 (rc)

[wellwelwel]

Version: Deno 2.0.0-rc.1

I noticed that, in version 2, I can run .cjs files, but not .cts files. Using any version from 1.x.x onwards, including the latest (1.46.3), both runs work fine.

I'd like to understand it better:

Is it intentional to accept .cjs but not .cts (not an issue), should both not be supported or should both work as in previous major version?

The message error:

Expected a JavaScript or TypeScript module, but identified a Cts module. Importing these types of modules is currently not supported.

• Perhaps "unrecognized" fits better than "not supported" for this report.
• This error doesn't occur during import, but with the deno run command.

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For a brief context, these tests are totally empty files, just to make sure that a test runner is properly targeting each file by extension according to how each runtime (Node.js, Bun and Deno) handles them.

Before v2 (1.46.3):

After v2 (2.0.0-rc.1):

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Minimal Reproduction

test.cts

console.log(123);

deno run test.cts

Output:

error: Expected a JavaScript or TypeScript module, but identified a Cts module. Importing these types of modules is currently not supported.
  Specifier: file:///***/test.cts

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Being my first issue here, thanks for Deno 🦕💙

[wesbos]

hitting this as well in an app where 1 file must be a commonJS file due to some limitations on ESM module cache, but I'd also like for it to be TypeScript. No way around this right now?

[dsherret]

Not at the moment. We put it off because the use of cts files seems low at the moment (https://github.com/search?type=code&q=path%3A*.cts), but we'd like to do it soon.

[wesbos]

Ah yeah, makes sense. I ended up just stripping the types from that file but it turns out I don't even need any of the weird cache stuff I'm doing in Node because of hmr in deno.

[dsherret]

I have a draft PR here: https://github.com/denoland/deno/pull/26558