Incomprehensible "imported by" noise when package doesn't exist

[philderbeast]

Using this repo' for the repro', I can't make sense of this "using configuration(s) from" message.

$ echo "packages: pkg-doesnt-exist" >> cabal.project

$ cabal build pkg-doesnt-exist --dry-run
When using configuration(s) from cabal.project, project-cabal/constraints.config
  imported by: cabal.project, project-cabal/ghc-latest.config
  imported by: cabal.project, project-cabal/ghc-options.config
  imported by: cabal.project, project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/benchmarks.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/buildinfo.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/cabal.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/install.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/integration-tests.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, project-cabal/pkgs/tests.config
  imported by: project-cabal/pkgs.config
  imported by: cabal.project, the following errors occurred:
The package location 'pkg-doesnt-exist' does not exist.

$ git rev-parse HEAD
570960c448f08f91b647a2d5182c7ca89f32dddb

[philderbeast]

It looks like a formatting problem. The message is more legible with the indenting fixed;

$ cabal build pkg-doesnt-exist --dry-run
When using configuration(s) from: 
  cabal.project
  project-cabal/constraints.config
    imported by: cabal.project
  project-cabal/ghc-latest.config
    imported by: cabal.project
  project-cabal/ghc-options.config
    imported by: cabal.project
  project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/benchmarks.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/buildinfo.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/cabal.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/install.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/integration-tests.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
  project-cabal/pkgs/tests.config
    imported by: project-cabal/pkgs.config
    imported by: cabal.project
The following errors occurred:
The package location 'pkg-doesnt-exist' does not exist.

[philderbeast]

This would be even more legible as a tree (as originally envisaged and if we could display unicode) 😭

$ tree -P '*.project|*.config' --prune -L 3
...
└── project-cabal
    ├── constraints.config
    ├── ghc-latest.config
    ├── ghc-options.config
    ├── pkgs
    │   ├── benchmarks.config
    │   ├── buildinfo.config
    │   ├── cabal.config
    │   ├── install.config
    │   ├── integration-tests.config
    │   └── tests.config
    └── pkgs.config

[philderbeast]

I'm working on a fix where the output looks like a tree but we could fallback to displaying a list too;

When using configuration(s) from:
  cabal.project
  project-cabal/
    constraints.config
    ghc-latest.config
    ghc-options.config
    pkgs.config
    pkgs/
      benchmarks.config
      buildinfo.config
      cabal.config
      install.config
      integration-tests.config
      tests.config
The following errors occurred:
  - The package location 'pkg-doesnt-exist' does not exist.