× invalid turbo json Error: × No "extends" key found if `./` is specified in the pnpm-workspace packages

Verify canary release

[X] I verified that the issue exists in the latest Turborepo canary release.

Link to code that reproduces this issue

https://github.com/aminya/temp-turbo-pnpm-bug

What package manager are you using / does the bug impact?

pnpm

What operating system are you using?

Linux

Which canary version will you have in your reproduction?

2.0.14

Describe the Bug

When ./ is specified in the packages list in pnpm-workspace.yaml, turbo gives this error. This is very confusing and doesn't provide any info on what the issue is. From the pnpm perspective, ./ is a valid package, but even if turbo doesn't accept this, it should provide a better error message.

turbo 2.0.14

  × invalid turbo json

Error:   × No "extends" key found
    ╭─[turbo.json:1:1]
  1 │ ╭─▶ {
  2 │ │     "$schema": "https://turbo.build/schema.json",
  3 │ │     "tasks": {
  4 │ │       "build": {
  5 │ │         "dependsOn": [
  6 │ │           "prebuild",
  7 │ │           "^build"
  8 │ │         ],
  9 │ │         "outputs": [
 10 │ │           "output-file.txt",
 11 │ │           "dist/**"
 12 │ │         ]
 13 │ │       },
 14 │ │       "prebuild": {},
 15 │ │       "lint": {},
 16 │ │       "type-check": {}
 17 │ │     }
 18 │ ├─▶ }
    · ╰──── add extends key here
    ╰────

Expected Behavior

Work without issues or provide a better error

To Reproduce

pnpm i
pnpm exec turbo build

Additional context

No response

vercel / turborepo

× invalid turbo json Error: × No "extends" key found if `./` is specified in the pnpm-workspace packages #9017