From bedabfbcef9285804729aa78f933d8ceb4897ecf Mon Sep 17 00:00:00 2001
From: Guillaume Girol <symphorien+git@xlumurb.eu>
Date: Sun, 13 Feb 2022 12:00:00 +0000
Subject: [PATCH] rustPlatform.bindgenHook: init

---
 doc/languages-frameworks/rust.section.md            |  2 ++
 pkgs/build-support/rust/hooks/default.nix           | 10 ++++++++++
 pkgs/build-support/rust/hooks/rust-bindgen-hook.sh  | 13 +++++++++++++
 .../compilers/rust/make-rust-platform.nix           |  2 +-
 pkgs/development/tools/rust/bindgen/default.nix     |  4 +++-
 5 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 pkgs/build-support/rust/hooks/rust-bindgen-hook.sh

diff --git a/doc/languages-frameworks/rust.section.md b/doc/languages-frameworks/rust.section.md
index 56faf636df10..e19783e29e6a 100644
--- a/doc/languages-frameworks/rust.section.md
+++ b/doc/languages-frameworks/rust.section.md
@@ -464,6 +464,8 @@ you of the correct hash.
   be disabled by setting `dontUseCargoParallelTests`.
 * `cargoInstallHook`: install binaries and static/shared libraries
   that were built using `cargoBuildHook`.
+* `bindgenHook`: for crates which use `bindgen` as a build dependency, lets
+  `bindgen` find `libclang` and `libclang` find the libraries in `buildInputs`.
 
 ### Examples {#examples}
 
diff --git a/pkgs/build-support/rust/hooks/default.nix b/pkgs/build-support/rust/hooks/default.nix
index d86c9ebaed80..d33692457077 100644
--- a/pkgs/build-support/rust/hooks/default.nix
+++ b/pkgs/build-support/rust/hooks/default.nix
@@ -1,6 +1,7 @@
 { buildPackages
 , callPackage
 , cargo
+, clang
 , diffutils
 , lib
 , makeSetupHook
@@ -92,4 +93,13 @@ in {
           rustBuildPlatform rustTargetPlatform rustTargetPlatformSpec;
       };
     } ./maturin-build-hook.sh) {};
+
+    bindgenHook = callPackage ({}: makeSetupHook {
+      name = "rust-bindgen-hook";
+      substitutions = {
+        libclang = clang.cc.lib;
+        inherit clang;
+      };
+    }
+    ./rust-bindgen-hook.sh) {};
 }
diff --git a/pkgs/build-support/rust/hooks/rust-bindgen-hook.sh b/pkgs/build-support/rust/hooks/rust-bindgen-hook.sh
new file mode 100644
index 000000000000..53624b124f2b
--- /dev/null
+++ b/pkgs/build-support/rust/hooks/rust-bindgen-hook.sh
@@ -0,0 +1,13 @@
+# populates LIBCLANG_PATH and BINDGEN_EXTRA_CLANG_ARGS for rust projects that
+# depend on the bindgen crate
+
+# if you modify this, you probably also need to modify the wrapper for the cli
+# of bindgen in pkgs/development/tools/rust/bindgen/wrapper.sh
+
+populateBindgenEnv () {
+    export LIBCLANG_PATH=@libclang@/lib
+    BINDGEN_EXTRA_CLANG_ARGS="$(< @clang@/nix-support/cc-cflags) $(< @clang@/nix-support/libc-cflags) $(< @clang@/nix-support/libcxx-cxxflags) $NIX_CFLAGS_COMPILE"
+    export BINDGEN_EXTRA_CLANG_ARGS
+}
+
+postHook="${postHook:-}"$'\n'"populateBindgenEnv"$'\n'
diff --git a/pkgs/development/compilers/rust/make-rust-platform.nix b/pkgs/development/compilers/rust/make-rust-platform.nix
index f479b052019e..2071c48cc6d5 100644
--- a/pkgs/development/compilers/rust/make-rust-platform.nix
+++ b/pkgs/development/compilers/rust/make-rust-platform.nix
@@ -31,5 +31,5 @@ rec {
   # Hooks
   inherit (callPackage ../../../build-support/rust/hooks {
     inherit stdenv cargo rustc;
-  }) cargoBuildHook cargoCheckHook cargoInstallHook cargoSetupHook maturinBuildHook;
+  }) cargoBuildHook cargoCheckHook cargoInstallHook cargoSetupHook maturinBuildHook bindgenHook;
 }
diff --git a/pkgs/development/tools/rust/bindgen/default.nix b/pkgs/development/tools/rust/bindgen/default.nix
index 782996d92180..444db1173225 100644
--- a/pkgs/development/tools/rust/bindgen/default.nix
+++ b/pkgs/development/tools/rust/bindgen/default.nix
@@ -34,7 +34,9 @@ let
           touch $out
         '';
       };
-    } ''
+    }
+    # if you modify the logic to find the right clang flags, also modify rustPlatform.bindgenHook
+    ''
     mkdir -p $out/bin
     export cincludes="$(< ${clang}/nix-support/cc-cflags) $(< ${clang}/nix-support/libc-cflags)"
     export cxxincludes="$(< ${clang}/nix-support/libcxx-cxxflags)"