Last pnpm version that worked

9.8.0

pnpm version

11.5.0

Code to reproduce the issue

pnpm i typescript@6.0.3 xo@2.0.2
cd -P node_modules/xo/../typescript-eslint/../@typescript-eslint/eslint-plugin/../..
jq .version typescript/package.json @typescript-eslint/parser/../../typescript/package.json

Expected behavior

$ jq .version typescript/package.json @typescript-eslint/parser/../../typescript/package.json
"5.9.3"
"5.9.3"

flowchart
  A("@typescript-eslint/eslint-plugin") -->|peer-depends| B("@typescript-eslint/parser")
  A -->|peer-depends| C(typescript)
  B -->|peer-depends| C

@typescript-eslint/eslint-plugin peer-depends typescript, and it also peer-depends @typescript-eslint/parser which peer-depends typescript, so these are expected to resolve to the same version of typescript. This was the behavior of pnpm 9.8.0 and earlier.

Actual behavior

$ jq .version typescript/package.json @typescript-eslint/parser/../../typescript/package.json
"5.9.3"
"6.0.3"

This typescript version mismatch leads to a crash at runtime in xo: TypeError: tsutils.unionConstituents is not a function or its return value is not iterable. For details and reproduction, see

• TypeError: tsutils.unionConstituents is not a function or its return value is not iterable xojs/xo#880

Additional information

This regression was introduced by

• fix: out-of-memory on peers resolution #8457

Node.js version

24.15.0

Operating System

Linux