Install the Haskell SDK

Prerequisites

GHC 9.12.2 and Cabal (the binding builds with cabal-version: 3.8). The FFI backend also needs a Rust toolchain when building libpanproto_c from source; rustup is recommended.

The panproto package is not yet on a registry; it lives at bindings/haskell/ in the repository and you build it from there. The default rust flag links the FFI backend against libpanproto_c, so the library has to be staged first. There are two ways to get it.

Build from source

bootstrap/dev-link.sh builds panproto-c from the workspace with cargo build -p panproto-c --release, compiles the panproto-glue C layer into a standalone libpanproto_glue.a, and stages both under bindings/haskell/.panproto-c/. It then writes a gitignored cabal.project.local carrying the absolute lib and include paths (cabal’s relative extra-lib-dirs propagate into ghc-pkg’s registration metadata, which rejects anything but absolute paths).

git clone https://github.com/panproto/panproto.git
cd panproto/bindings/haskell
./bootstrap/dev-link.sh                # builds panproto-c, stages libs
cabal build
cabal test

Run dev-link.sh again after every change to panproto-c, to the C glue, or to the workspace Cargo.toml.

Prebuilt binaries

bootstrap/fetch-bindist.sh [version] downloads the prebuilt libpanproto_c for the host platform from the corresponding GitHub Release (it detects aarch64-apple-darwin, x86_64-apple-darwin, x86_64-unknown-linux-gnu, and aarch64-unknown-linux-gnu), rebuilds the C glue against the fetched header, and writes the same cabal.project.local. No Rust toolchain is needed on this path.

git clone https://github.com/panproto/panproto.git
cd panproto/bindings/haskell
./bootstrap/fetch-bindist.sh           # downloads + stages the platform tarball
cabal build
cabal test

Native-only (no FFI)

For the pure-Haskell subset (the protocol and schema round-trip and the value algebra), disable the FFI backend. This build needs no libpanproto_c and no Rust toolchain:

cabal build -f-rust

Verification

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DuplicateRecordFields #-}

import qualified Panproto.Schema as S

main :: IO ()
main = do
    let s = S.buildSchema "geojson" $ do
                S.vertex S.Vertex {S.id = "post", S.kind = "record", S.nsid = Nothing}
    print (S.vertexCount s)

cabal run builds and links against the staged libraries. Building a one-vertex structured schema and printing its vertex count exercises the pure value algebra without touching the engine, so it succeeds under every flag configuration, the native-only build included.

Common mistakes

A shadowed ld on PATH. Anaconda and some other Python distributions ship their own ld, which is too old to recognize the response-file syntax GHC’s merge-objects pass uses; the symptom is a ld: file not found: @<tmp>/ghc_tmp_*.rsp error during cabal build on macOS arm64. dev-link.sh warns when ld resolves to something other than the system linker. Prepend /usr/bin to PATH and retry.
Skipping the bootstrap step on a default (rust-flag) build. Without dev-link.sh or fetch-bindist.sh, no cabal.project.local exists, extra-lib-dirs is unset, and the link fails on the missing libpanproto_c.
A relative extra-lib-dirs. The path in cabal.project.local is absolute by design; ghc-pkg refuses a relative one during package registration.

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