support conditional compilation of Nix C APIs

nixide-sys/Cargo.toml

@@ -19,14 +19,16 @@ targets = [ "x86_64-unknown-linux-gnu" ]
 [lib]
 path = "lib.rs"
 
+# NOTE: `[features]` have a 1-1 correspondence to the
+# NOTE: shared libraries produced by the Nix C API.
 [features]
-default = ["util"]
-expr = []
-fetchers = []
-flakes = []
-store = []
-util = []
-gc = []
+default = ["nix-util-c"]
+nix-util-c = []
+nix-store-c = []
+nix-expr-c = []
+nix-fetchers-c = []
+nix-flake-c = []
+nix-main-c = []
 
 [build-dependencies]
 bindgen              = { default-features = false, features = [ "logging", "runtime" ], version = "0.72.1" }

nixide-sys/build.rs

@@ -20,17 +20,26 @@ impl ParseCallbacks for DoxygenCallbacks {
 
 fn main() {
     // Invalidate the built crate whenever the wrapper changes
-    println!("cargo:rerun-if-changed=include/wrapper.h");
+    println!("cargo:rerun-if-changed=include/nix-util.h");
+    println!("cargo:rerun-if-changed=include/nix-store.h");
+    println!("cargo:rerun-if-changed=include/nix-expr.h");
+    println!("cargo:rerun-if-changed=include/nix-fetchers.h");
+    println!("cargo:rerun-if-changed=include/nix-flake.h");
+    println!("cargo:rerun-if-changed=include/nix-main.h");
 
-    // Use pkg-config to find nix-store include and link paths
-    // This NEEDS to be included, or otherwise `nix_api_store.h` cannot
-    // be found.
     let libs = [
-        "nix-main-c",
-        "nix-expr-c",
-        "nix-store-c",
+        #[cfg(feature = "nix-util-c")]
         "nix-util-c",
+        #[cfg(feature = "nix-store-c")]
+        "nix-store-c",
+        #[cfg(feature = "nix-expr-c")]
+        "nix-expr-c",
+        #[cfg(feature = "nix-fetchers-c")]
+        "nix-fetchers-c",
+        #[cfg(feature = "nix-flake-c")]
         "nix-flake-c",
+        #[cfg(feature = "nix-main-c")]
+        "nix-main-c",
     ];
 
     let lib_args: Vec<String> = libs
@@ -50,17 +59,43 @@ fn main() {
         .flatten()
         .collect();
 
-    let bindings = bindgen::Builder::default()
+    let mut builder = bindgen::Builder::default()
         .clang_args(lib_args)
-        // The input header we would like to generate bindings for
-        .header("include/wrapper.h")
         // Invalidate the built crate when an included header file changes
         .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
         // Add `doxygen_bindgen` callbacks
         .parse_callbacks(Box::new(DoxygenCallbacks))
         // Format generated bindings with rustfmt
         .formatter(bindgen::Formatter::Rustfmt)
-        .rustfmt_configuration_file(std::fs::canonicalize(".rustfmt.toml").ok())
+        .rustfmt_configuration_file(std::fs::canonicalize(".rustfmt.toml").ok());
+
+    // The input headers we would like to generate bindings for
+    #[cfg(feature = "nix-util-c")]
+    {
+        builder = builder.header("include/nix-util.h")
+    }
+    #[cfg(feature = "nix-store-c")]
+    {
+        builder = builder.header("include/nix-store.h")
+    }
+    #[cfg(feature = "nix-expr-c")]
+    {
+        builder = builder.header("include/nix-expr.h")
+    }
+    #[cfg(feature = "nix-fetchers-c")]
+    {
+        builder = builder.header("include/nix-fetchers.h")
+    }
+    #[cfg(feature = "nix-flake-c")]
+    {
+        builder = builder.header("include/nix-flake.h")
+    }
+    #[cfg(feature = "nix-main-c")]
+    {
+        builder = builder.header("include/nix-main.h")
+    }
+
+    let bindings = builder
         // Finish the builder and generate the bindings
         .generate()
         // Unwrap the Result and panic on failure

nixide-sys/include/nix-expr.h

@@ -0,0 +1,10 @@
+// Nix C API for the Nix expressions evaluator.
+#include <nix_api_expr.h>
+
+// Nix C API for value manipulation.
+//
+#include <nix_api_value.h>
+
+// Nix C API for external values.
+//
+#include <nix_api_external.h>

nixide-sys/include/nix-fetchers.h

@@ -0,0 +1,3 @@
+// Nix C API for fetcher operations.
+//
+#include <nix_api_fetchers.h>

nixide-sys/include/nix-flake.h

@@ -0,0 +1,3 @@
+// Nix C API for flake support.
+//
+#include <nix_api_flake.h>

nixide-sys/include/nix-main.h

@@ -0,0 +1,3 @@
+// Nix C API for CLI support.
+//
+#include <nix_api_main.h>

nixide-sys/include/nix-store.h

@@ -0,0 +1,3 @@
+// Nix C API for store operations.
+//
+#include <nix_api_store.h>

nixide-sys/include/nix-util.h

@@ -0,0 +1,7 @@
+// Nix C API for utilities.
+//
+// Most notably containing functions for handling
+// the `nix_c_context` structure, which is used throughout
+// the Nix C APIs for error handling.
+//
+#include <nix_api_util.h>

nixide-sys/include/wrapper.h

@@ -1,23 +0,0 @@
-// Pure C API for store operations
-#include <nix_api_store.h>
-
-// Pure C API for error handling
-#include <nix_api_util.h>
-
-// Pure C API for the Nix evaluator
-#include <nix_api_expr.h>
-
-// Pure C API for external values
-#include <nix_api_external.h>
-
-// Pure C API for value manipulation
-#include <nix_api_value.h>
-
-// Pure C API for fetcher operations
-#include <nix_api_fetchers.h>
-
-// Pure C API for flake support
-#include <nix_api_flake.h>
-
-// Pure C API for main/CLI support
-#include <nix_api_main.h>