Issue: typescript is not listed in peerDependencies

[Rulexec]

I use pnpm with fully isolated dependencies of dependencies. I also have a rule for circular imports that are not type‑only, but somehow type‑only imports trigger the circular import rule.

After debugging I found trying to import typescript which fails because dependency-cruiser is does not list typescript as a dependency.

Expected Behavior

Using type-only should fail if typescript package is not available, and it should provide a clear error message explaining this.

Current Behavior

It ignores import type statements and does not detect them as type‑only imports.

Possible Solution

I resolved this issue by using a pnpm package extension:

  "pnpm": {
    "packageExtensions": {
      "dependency-cruiser": {
        "peerDependencies": {
          "typescript": "*"
        }
      }
    }
  },

Perhaps dependency-cruiser should declare typescript in its peerDependencies?

Your Environment

• Version used: 17.3.9
• Node version: 22.14.0
• Typescript version: 5.9.3
• pnpm version: 10.14.0

Sorry, I cannot share my pnpm config because, in my environment, it’s not straightforward — I don’t use pnpm directly. Maybe on Saturday, I’ll try to create a minimal demo.

Thanks.

[sverweij]

Hi @Rulexec thanks for reaching out (and sorry for me taking 3 weeks to reply).

dependency-cruiser supports, apart from javascript, an array of compile-to-javascript languages. TypeScript is one of them. If it'd mention each of them as a peer dependency the installed size would become quite large (npm blindly installs them, and I wouldn't be surprised if other package managers have followed suit) - and it would be great for start-up (and run) performance, despite efforts to lazy load only (e.g. see what the ancient but certainly not even close to dead-yet coffeescript transpiler does when it's merely present )

Usually, in the past ~10 years the environments dependency-cruiser was installed in would typically already have the right transpilers available and the auto-detection worked fine.

Recently there seems to be a trend to use typetripping-only transpilers (e.g. esbuild, swc) and not install the TypeScript one (the only transpiler that does actual type checking a.f.a.ik.) itself - usually to speed up builds. This, combined with the prevalence of TypeScript these days dependency-cruiser will need to be adjusted a bit. The path forward for now is to include a warning in the output to install the correct transpiler when it finds a module that is in a language it doesn't have a transpiler for (e.g. see #1048)