maybe/optional example

things I've changed from the PR:
- dropped legacy (i.e. non-flake) compat stuff, which turns out to account for most of the diff
- dropped `packages.garnet` since it doesn't work with `nix build .#garnet`
- back to using Rust-extended packages everywhere, which _seems_ fine
the rest is just re-inlining things and other refactors

note that changes we keep are essentially:
- not using Crane's extended packages everywhere
- bumping `nix-haskell` to avoid shell hook workaround
- various changes in how we call `nix-haskell`
- using `libCgarnet_rs` name, which Cabal expects
- adding proper non-dev-shell targets, so that e.g. `nix run` works

stuff we should still take a look at:
- seems a bit weird that `garnet-rs` arg to `project.nix` was always same (and therefore now we always pass the ) - might be a mistake, and we're supposed to be using local for local build?
- similar `libCgarnet_rs.a` logic appears in three places - see if we can deduplicate to some extent somehow
- I haven't even checked all steps are necessary

exe/Main.hs

@@ -9,8 +9,6 @@ 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)

flake.lock

@@ -527,16 +527,15 @@
     "hs-bindgen-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1774599157,
-        "narHash": "sha256-jgV67xhWzxMwyiyy5RPtu+VQvGTt+FoMXCWJcZ7lczY=",
+        "lastModified": 1774379170,
+        "narHash": "sha256-lZV6IdCBf8uCt21qB5mfgLaP9CNgho/HsqjvkulDR2Q=",
         "owner": "well-typed",
         "repo": "hs-bindgen",
-        "rev": "3c4af10590d0d09e825a9735e9a03d7f60914e21",
+        "rev": "4b6febb5cc6196835bd2890a3ab27a88dab1806b",
         "type": "github"
       },
       "original": {
         "owner": "well-typed",
-        "ref": "release-0.1-alpha2",
         "repo": "hs-bindgen",
         "type": "github"
       }
@@ -561,11 +560,11 @@
     "libclang-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1774600891,
-        "narHash": "sha256-LTAyNMY4Vu0vPeEq2wXB0KWY4kGtqtHTRmADjLdkv78=",
+        "lastModified": 1774018529,
+        "narHash": "sha256-Bo5wvityXKCmlnrobtI9WkA1maR7sfkDXo1VOZvrPLk=",
         "owner": "well-typed",
         "repo": "libclang",
-        "rev": "1054474fae403bfb52c7919680cac03d3d3d4237",
+        "rev": "83387d72a8dfae9f75d27db6b32ea37afab06268",
         "type": "github"
       },
       "original": {

flake.nix

@@ -3,7 +3,7 @@
     nix-haskell.url = "github:reflex-frp/nix-haskell";
     nixpkgs.follows = "nix-haskell/nixpkgs";
     hls-src = { url = "github:haskell/haskell-language-server/2.13.0.0"; flake = false; };
-    hs-bindgen-src = { url = "github:well-typed/hs-bindgen/release-0.1-alpha2"; flake = false; };
+    hs-bindgen-src = { url = "github:well-typed/hs-bindgen"; flake = false; };
     libclang-src = { url = "github:well-typed/libclang"; flake = false; };
     flake-utils.url = "github:numtide/flake-utils";
     crane.url = "github:ipetkov/crane";

garnet.cabal

@@ -6,13 +6,6 @@ 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
@@ -50,13 +43,11 @@ 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,
         hs-bindgen-runtime,
+        primitive,
         template-haskell,
 
 executable garnet

lib/GarnetRs/Raw.hs

@@ -1,5 +1,6 @@
 {-# LANGUAGE CApiFFI #-}
 {-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE FieldSelectors #-}
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE TemplateHaskell #-}
@@ -29,15 +30,7 @@ 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

@@ -1,20 +1,11 @@
-{-# 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,
@@ -47,6 +38,7 @@ data Shape
 convertShape :: Shape -> Raw.Shape
 convertShape = \case
     Circle r -> Raw.Shape Raw.Circle $ Raw.set_shape_circle_circle $ Raw.Circle_Body r
+    -- hmm, unintuitive name
     Rectangle w h -> Raw.Shape Raw.Rectangle $ Raw.set_shape_circle_rectangle $ Raw.Rectangle_Body w h
 
 data BTree a
@@ -71,9 +63,6 @@ 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
 

rust/build.rs

@@ -2,22 +2,6 @@ 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

@@ -11,7 +11,7 @@ fn say_hello(name: &str) {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello(c: *const c_char) {
+extern "C" fn hello(c: *const c_char) -> () {
     say_hello(unsafe { CStr::from_ptr(c) }.to_str().unwrap())
 }
 
@@ -23,23 +23,10 @@ struct T {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_struct(t: &T) {
+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 {
@@ -48,7 +35,7 @@ enum Shape {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn hello_shape(s: &Shape) {
+extern "C" fn hello_shape(s: &Shape) -> () {
     say_hello(&format!("{:?}", s))
 }
 
@@ -93,7 +80,7 @@ enum BTreeC {
 
 #[unsafe(no_mangle)]
 extern "C" fn sum_tree(t: &BTreeC) -> i64 {
-    (unsafe { std::mem::transmute::<&BTreeC, &BTree<i64>>(t) }).sum()
+    (unsafe { std::mem::transmute::<_, &BTree<i64>>(t) }).sum()
 }
 
 #[unsafe(no_mangle)]
@@ -102,8 +89,9 @@ extern "C" fn sum_slice(v: *const i64, s: usize) -> i64 {
 }
 
 #[unsafe(no_mangle)]
-extern "C" fn print_optional(x: Option<&i8>) {
-    if let Some(x) = x {
-        println!("{}", x / 2)
+extern "C" fn print_optional(x: Option<&i8>) -> () {
+    match x {
+        Some(x) => println!("{}", x / 2),
+        None => {}
     }
 }