Haskell — eitherParsec error using cabal update

Once in a while, I try new things and this time is playing with Haskell, cabal, and Plutus Pioneer program.

In WSL2 with Ubuntu, I got this error using cabal.project file from Plutus Pioneer Program GitHub repo when simply running cabal update :

“<eitherParsec>” (line 2, column 1):
unexpected ‘p’
expecting space or end of input

The error occurred on this block near subdir:

...
source-repository-package
  type: git
  location: https://github.com/input-output-hk/plutus.git
  subdir:
    freer-extras
    playground-common
    plutus-chain-index
    plutus-core
    plutus-contract
    plutus-ledger
    plutus-ledger-api
    plutus-tx
    plutus-tx-plugin
    prettyprinter-configurable
    quickcheck-dynamic
    word-array
  tag: ea0ca4e9f9821a9dbfc5255fa0f42b6f2b3887c4
...

The “fix” (if we can call this a fix…) is to use subdir on each line like this:

source-repository-package
  type: git
  location: https://github.com/input-output-hk/plutus.git
  subdir: freer-extras
  subdir: playground-common
  subdir: plutus-chain-index
  subdir: plutus-core
  subdir: plutus-contract
  subdir: plutus-ledger
  subdir: plutus-ledger-api
  subdir: plutus-tx
  subdir: plutus-tx-plugin
  subdir: prettyprinter-configurable
  subdir: quickcheck-dynamic
  subdir: word-array
  tag: 81ba78edb1d634a13371397d8c8b19829345ce0d

I hope it will help someone not wasting as much time as myself on such compatibility error (cabal version was old, GHC also).

Specifically for the Plutus Pioneer repo, this error can be avoided using Nix-shell. It solves a lot of issues and run perfectly within WSL2 (with bash shell).

Tools versions:

• GHC — The Glorious Glasgow Haskell Compilation System, version 8.8.4
• cabal — cabal-install version 3.0.0.0
• Ubuntu — Ubuntu 21.04