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Uses ghcOverride to point at nixpkgs' prebuilt GHC instead of letting haskell-nix.compiler.* build its own patched GHC from source via hadrianProject, which needs IFD to evaluate regardless of GHC version or materialization (verified directly against haskell.nix's own flake). Also materializes the project's own cabal plan (haskell.nix/materialized/ plan.nix) and pins haskellNix to a revision whose nixpkgs-unstable still has spdx-license-list-data 3.27.0, matching haskell.nix's last materialized SPDX cache — newer nixpkgs-unstable ships 3.28.0, which haskell.nix hasn't materialized yet. Drops the mingwW64 (Windows) cross-compilation target: haskell.nix's materialized iserv-proxy (needed for cross-compiled TemplateHaskell support) doesn't cover ghc966/ghc967, so it falls back to an unmaterialized IFD build. The musl64 target is unaffected and kept. allow-import-from-derivation = true is no longer needed for this template specifically, though it stays enabled globally in CI since haskell-flake (a different mechanism, callCabal2nix-based) still requires it. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
tomberek
marked this pull request as draft
September 14, 2026 05:25
builder/default.nix's hoogleLocal reads ghc.buildGHC unconditionally (not ghc.buildGHC or ghc, unlike other call sites), which nixpkgs' plain GHC lacks, breaking hydraJobs.x86_64-unknown-linux-musl. Point buildGHC at itself to match what haskell.nix's own compilers carry. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
tomberek
marked this pull request as ready for review
September 14, 2026 06:03
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Summary
ghcOverrideto point at nixpkgs' prebuilt GHC instead of building haskell.nix's own patched GHC from source viahadrianProject, which needs IFD to evaluate regardless of GHC version or materialization (verified directly against haskell.nix's own flake, independent of this template).haskell.nix/materialized/plan.nix).haskellNixto a revision whosenixpkgs-unstablestill hasspdx-license-list-data3.27.0, matching haskell.nix's last materialized SPDX cache (newernixpkgs-unstableships 3.28.0, which haskell.nix hasn't materialized yet).mingwW64(Windows) cross-compilation target: haskell.nix's materializediserv-proxydoesn't cover ghc966/ghc967 yet, so it falls back to an unmaterialized IFD build. Themusl64target is unaffected and kept.allow-import-from-derivation = trueis no longer needed for this template specifically, though it stays enabled globally in CI sincehaskell-flake(a different,callCabal2nix-based mechanism) still requires it.Test plan
nix flake check --option allow-import-from-derivation falsepasses with zero IFD errorsnix flake show --option allow-import-from-derivation falsepassesnix build --option allow-import-from-derivation false .#defaultbuilds and runs the executable successfully