basic enum example

exe/Main.hs

@@ -9,6 +9,8 @@ main = do
     hello "Haskell"
     helloStruct T{a = True, b = 42}
     helloStruct T{a = False, b = maxBound}
+    helloEnum E1
+    helloEnum E3
     helloShape $ Circle 3.14
     helloShape $ Rectangle 10.0 5.0
     putStrLn $ "3 + 4 = " <> show (add 3 4)

garnet.cabal

@@ -6,6 +6,13 @@ author: Patrick Aldis
 maintainer:
     george.thomas@obsidian.systems
     patrick.aldis@obsidian.systems
+-- aha, nice, this does fix recompilation checking
+extra-source-files:
+    rust/target/debug/garnet_rs.h
+-- that could be problematic given file is gitignored? unfortunately this doesn't work
+-- tbf, I haven't even looked up the docs, just saw the autocompletion
+-- extra-tmp-files:
+--     rust/target/debug/garnet_rs.h
 
 common common
     default-language: GHC2024
@@ -43,6 +50,9 @@ library
         GarnetRs.Wrapped
     hs-source-dirs: lib
     include-dirs: rust/target/debug
+    -- HLS gives up entirely when the header is malformed if we do this
+    -- and anyway, I don't think it gives us dependency tracking like `extra-source-files` does
+    -- includes: garnet_rs.h
     extra-bundled-libraries: Cgarnet_rs
     build-depends:
         hs-bindgen,

lib/GarnetRs/Raw.hs

@@ -29,7 +29,15 @@ import HsBindgen.TH
 import Language.Haskell.TH
 import System.Process
 
+import Control.Monad.IO.Class (MonadIO (liftIO))
+import Language.Haskell.TH.Syntax (addDependentFile)
+import System.Directory.Extra (getCurrentDirectory)
+
 do
+    -- not sure this does anything - hs-bindgen should already be doing the tracking, and the issues are from elsewhere
+    -- dir <- liftIO getCurrentDirectory
+    -- liftIO $ print dir
+    -- addDependentFile $ dir <> "/rust/target/debug/garnet_rs.h"
     systemDirs <- -- TODO bit of a hack
         map (Dir . T.unpack . T.strip)
             . concatMap (takeWhile (maybe False ((== ' ') . fst) . T.uncons) . dropWhile T.null . T.lines)

lib/GarnetRs/Wrapped.hs

@@ -1,11 +1,20 @@
+{-# LANGUAGE PatternSynonyms #-}
+
 -- TODO automate this sort of high level wrapper boilerplate
 -- or look at upstream plans: https://github.com/well-typed/hs-bindgen/issues?q=state%3Aopen%20label%3A%22highlevel%22
 module GarnetRs.Wrapped (
     T (..),
+    Raw.E (..),
+    -- TODO hmm, we don't really want to have to list all of these...
+    -- is there an option to make them not be patterns at all?
+    pattern Raw.E1,
+    pattern Raw.E2,
+    pattern Raw.E3,
     Shape (..),
     BTree (..),
     hello,
     helloStruct,
+    helloEnum,
     helloShape,
     add,
     sumTree,
@@ -62,6 +71,9 @@ hello = flip useAsCString $ Raw.hello . unsafeFromPtr
 helloStruct :: T -> IO ()
 helloStruct = flip with (Raw.hello_struct . unsafeFromPtr) . convertT
 
+helloEnum :: Raw.E -> IO ()
+helloEnum = flip with (Raw.hello_enum . unsafeFromPtr)
+
 helloShape :: Shape -> IO ()
 helloShape = flip with (Raw.hello_shape . unsafeFromPtr) . convertShape
 

project.nix

@@ -19,6 +19,8 @@
   };
   overrides = [
     ({ pkgs, ... }: {
+      # TODO get this upstreamed:
+      # https://input-output-hk.github.io/haskell.nix/tutorials/pkg-map.html#mapping-in-haskellnix
       packages.libclang-bindings.components.library = {
         build-tools = [ pkgs.llvmPackages.llvm ];
         libs = [ pkgs.llvmPackages.libclang ];

rust/build.rs

@@ -2,6 +2,22 @@ use std::env;
 use std::path::PathBuf;
 
 fn main() {
+    // this doesn't make _much_ difference really, since this is our only Rust source file
+    // but it seems it's probably better than not having it
+    // what we really want is to tell Rust to only regenerate the header file if the Rust code actually compiles
+    // but we don't have that flexibility
+    // and it's an issue because cbindgen tries to be fault-tolerant in some ways that don't even seem to make sense
+    //
+    // e.g. mis-spell "Option" as "Option" and you get
+    // void print_optional(Optio<const int8_t*> x);
+    // instead of
+    // void print_optional(const int8_t *x);
+    // and that's only an issue because in HLS TH dependent-file watching gives up after an error
+    // i.e. once the containing splice has thrown an exception once, the containing file needs a manual edit to kick it
+    // P.S. strings to stdout?! what a terrible API
+    // don't get me started in the discoverability of actually then using the terminal for debugging:
+    // println!("cargo::warning={:?}", env::var("OUT_DIR"));
+    println!("cargo::rerun-if-changed=lib.rs");
     let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
     let profile = env::var("PROFILE").unwrap();
     cbindgen::Builder::new()

rust/lib.rs

@@ -27,6 +27,19 @@ extern "C" fn hello_struct(t: &T) {
     say_hello(&format!("{:?}", t))
 }
 
+#[repr(C)]
+#[derive(Debug)]
+enum E {
+    E1,
+    E2,
+    E3,
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn hello_enum(e: &E) {
+    say_hello(&format!("{:?}", e))
+}
+
 #[repr(C)]
 #[derive(Debug)]
 enum Shape {