From c7f9ac49aee9f66b1137682d3568edfe03bad3d0 Mon Sep 17 00:00:00 2001
From: hhefesto <hhefesto@rdataa.com>
Date: Tue, 8 Sep 2026 09:41:46 -0600
Subject: [PATCH] haskell-language-server: build its closure in a Cabal-syntax
 3.14 scope

HLS 2.13's formatters, ormolu 0.8 and fourmolu 0.19, need Cabal-syntax
3.14 where the compilers bundle 3.10 (GHC 9.8) or 3.12 (GHC 9.10). Built
against the bundled one, the closure carries two Cabal-syntax instances and
Cabal refuses to configure haskell-language-server. Re-scope the closure
(haskell-language-server, hls-plugin-api, ghcide, hlint, ormolu, fourmolu,
lsp-types) onto Cabal-syntax and Cabal 3.14.2.0, with extensions 0.1.1.0
(the Cabal-syntax 3.14 release), a jailbroken cabal-install-parsers, and
ghc-paths kept on the bundled Cabal it only needs for Setup.hs. This is
nixpkgs' recipe from configuration-common.nix.

Also pair the versioned Cabal_3_14_2_0 and Cabal_3_16_1_0 with their own
Cabal-syntax, jailbreak hw-fingertree's deepseq bound for GHC 9.10, and
let HLS link its executables dynamically, without which the fixup check
finds an RPATH into /build.

Verified on haskell.packages.ghc9103Binary: haskell-language-server
2.13.0.0 builds, reports GHC 9.10.3, and its closure holds a single
Cabal-syntax (3.14.2.0).
---
 haskell-packages.nix | 53 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 49 insertions(+), 4 deletions(-)

diff --git a/haskell-packages.nix b/haskell-packages.nix
index c0d5606..3982a16 100644
--- a/haskell-packages.nix
+++ b/haskell-packages.nix
@@ -1,7 +1,52 @@
 # Post-processing overlay for per-package fixes.
 # Applied after auto-called packages from pkgs/.
-final: prev: {
-  # Add package-specific overrides here as needed.
-  # Example:
-  #   some-package = prev.some-package.override { doCheck = false; };
+final: prev:
+let
+  inherit (prev) lib pkgs;
+  hl = pkgs.haskell.lib.compose;
+
+  # haskell-language-server's formatters (ormolu 0.8, fourmolu 0.19) need
+  # Cabal-syntax 3.14 where the compilers bundle 3.10 (GHC 9.8) or 3.12 (GHC
+  # 9.10); with the bundled one, the closure ends up with two Cabal-syntax
+  # instances and Cabal refuses to configure. Build the whole closure in one
+  # 3.14 scope, the way nixpkgs' configuration-common.nix does.
+  hlsScope = lself: lsuper: {
+    Cabal-syntax = lself.Cabal-syntax_3_14_2_0;
+    Cabal = lself.Cabal_3_14_2_0;
+    # Bounded to Cabal-syntax < 3.13; picks 3.14 once the bound is lifted.
+    cabal-install-parsers = hl.doJailbreak lsuper.cabal-install-parsers;
+    # The default 0.1.0.2 wants Cabal 3.12; 0.1.1.0 is the Cabal-syntax 3.14 release.
+    extensions = hl.doJailbreak lself.extensions_0_1_1_0;
+    # Depends on Cabal for its Setup.hs only; keep the bundled one so there is
+    # a single ghc-paths in the set.
+    ghc-paths = lsuper.ghc-paths.override { Cabal = null; };
+  };
+  inHlsScope = names: lib.genAttrs names (name: prev.${name}.overrideScope hlsScope);
+  hlsClosure = inHlsScope [
+    "haskell-language-server"
+    "hls-plugin-api"
+    "ghcide"
+    "hlint"
+    "ormolu"
+    "fourmolu"
+    "lsp-types"
+  ];
+in
+{
+  # A versioned Cabal must be built against its own Cabal-syntax, not the
+  # compiler's bundled one.
+  Cabal_3_14_2_0 = prev.Cabal_3_14_2_0.override { Cabal-syntax = final.Cabal-syntax_3_14_2_0; };
+  Cabal_3_16_1_0 = prev.Cabal_3_16_1_0.override { Cabal-syntax = final.Cabal-syntax_3_16_1_0; };
+
+  # deepseq upper bound excludes the 1.5.1.0 that GHC 9.10 ships.
+  hw-fingertree = hl.doJailbreak prev.hw-fingertree;
+}
+// hlsClosure
+// {
+  # haskell-language-server links its executables dynamically by default; unless
+  # the builder is told so, the fixup check finds an RPATH into /build. Same
+  # override as nixpkgs' configuration-nix.nix.
+  haskell-language-server = hl.overrideCabal (_: {
+    enableSharedExecutables = true;
+  }) hlsClosure.haskell-language-server;
 }