We are still building some packages with aeson 1.5 which is a slight annoyance, so let's make a list and migrate them to 2.0 one by one!

Packages still using aeson 1.5:

• niv
• nix-linter
• vaultenv
• stack
• descriptive
• mattermost-api, matterhorn
• elmPackages
• spago, bower-json
• ghcjs

Packages that are failing because they don't support aeson 2.0 (but also haven't been overridden to use 1.5):

• ghcjs haskell.compiler.ghcjs has a broken dependency #166553
• jl
• hasura-graphql-engine (because of haskellPackages.graphql-parser)

cc @NixOS/haskell