Error trying to build with stack lts-24.1 (ghc-9.10.2)

[ciukstar]

I get an error when trying to build and install haskell-language-server from source with stack lts-24.1 (ghc-9.10.2)

haskell-language-server$ head -n 5 stack.yaml
resolver: lts-24.1 # ghc-9.10.2

packages:
  - .
  - ./hie-compat
haskell-language-server$
haskell-language-server$ stack clean && stack install

Error: [S-8664]
       Invalid flag specification:
       * Package cabal-add does not define the following flags (specified in the project-level configuration (e.g. stack.yaml)): cabal-syntax.
         No flags are defined by package cabal-add.
haskell-language-server$

Your environment

Which OS do you use?

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 24.04.2 LTS
Release:	24.04
Codename:	noble

$ uname -a
Linux <hostname> 6.8.0-64-generic #67-Ubuntu SMP PREEMPT_DYNAMIC Sun Jun 15 20:23:31 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Which version of GHC do you use and how did you install it?

$ stack ghc -- --version

Error: [S-8664]
       Invalid flag specification:
       * Package cabal-add does not define the following flags (specified in the project-level configuration (e.g. stack.yaml)): cabal-syntax.
         No flags are defined by package cabal-add.

$ head -n 5 stack.yaml
resolver: lts-24.1 # ghc-9.10.2

packages:
  - .
  - ./hie-compat

Which LSP client (editor/plugin) do you use?

emacs+lsp-mode

$ emacs --version
GNU Emacs 30.1
Copyright (C) 2025 Free Software Foundation, Inc.

Which version of HLS do you use and how did you install it?

Have you configured HLS in any way (especially: a hie.yaml file)?

No. I have not configured HLS or the hie.yaml file in any way.

Steps to reproduce

haskell-language-server$ git remote -v
origin	https://github.com/haskell/haskell-language-server.git (fetch)
origin	https://github.com/haskell/haskell-language-server.git (push)
haskell-language-server$ 
haskell-language-server$ git pull origin master
From https://github.com/haskell/haskell-language-server
 * branch                master     -> FETCH_HEAD
Already up to date.
haskell-language-server$ 
haskell-language-server$ stack clean && stack build

Error: [S-8664]
       Invalid flag specification:
       * Package cabal-add does not define the following flags (specified in the project-level configuration (e.g. stack.yaml)): cabal-syntax.
         No flags are defined by package cabal-add.
haskell-language-server$

Expected behaviour

Should compile as before with many previous versions.

Actual behaviour

Apparently there is some kind of configuration error.

Debug information

haskell-language-server$ stack clean && stack --verbose build

Error: [S-8664]
       Invalid flag specification:
       * Package cabal-add does not define the following flags (specified in the project-level configuration (e.g. stack.yaml)): cabal-syntax.
         No flags are defined by package cabal-add.
haskell-language-server$

[fendor]

Hi!

I think you need to add cabal-add-0.1 as an extra-deps. Sounds like lts-24.1 pulls in cabal-add-0.2 which HLS HEAD does not build with.

[ciukstar]

Hi!

I think you need to add cabal-add-0.1 as an extra-deps. Sounds like lts-24.1 pulls in cabal-add-0.2 which HLS HEAD does not build with.

I tried all the options suggested by "stack" until I came across one that I don't understand.
... I can wait until the problem is solved.

Thanks.