feat: expose DEP_NGINX_ vars to the high-level bindings

The example build script converts `DEP_NGINX_FEATURES`, `DEP_NGINX_OS`
and `DEP_NGINX_VERSION_NUMBER` received from `nginx-sys` to the `cfg`
values for conditional compilation.

See tests for usage examples.

Author: bavshin-f5

Cargo.lock

@@ -0,0 +1,46 @@
+/// Example buildscript for an nginx module.
+///
+/// Due to the limitations of cargo[1], this buildscript _requires_ adding `nginx-sys` to the
+/// direct dependencies of your crate.
+///
+/// [1]: https://github.com/rust-lang/cargo/issues/3544
+fn main() {
+    // Generate `ngx_os` and `ngx_feature` cfg values
+
+    // Specify acceptable values for `ngx_feature`
+    println!("cargo::rerun-if-env-changed=DEP_NGINX_FEATURES_CHECK");
+    println!(
+        "cargo::rustc-check-cfg=cfg(ngx_feature, values({}))",
+        std::env::var("DEP_NGINX_FEATURES_CHECK").unwrap_or("any()".to_string())
+    );
+    // Read feature flags detected by nginx-sys and pass to the compiler.
+    println!("cargo::rerun-if-env-changed=DEP_NGINX_FEATURES");
+    if let Ok(features) = std::env::var("DEP_NGINX_FEATURES") {
+        for feature in features.split(',').map(str::trim) {
+            println!("cargo::rustc-cfg=ngx_feature=\"{}\"", feature);
+        }
+    }
+
+    // Specify acceptable values for `ngx_os`
+    println!("cargo::rerun-if-env-changed=DEP_NGINX_OS_CHECK");
+    println!(
+        "cargo::rustc-check-cfg=cfg(ngx_os, values({}))",
+        std::env::var("DEP_NGINX_OS_CHECK").unwrap_or("any()".to_string())
+    );
+    // Read operating system detected by nginx-sys and pass to the compiler.
+    println!("cargo::rerun-if-env-changed=DEP_NGINX_OS");
+    if let Ok(os) = std::env::var("DEP_NGINX_OS") {
+        println!("cargo::rustc-cfg=ngx_os=\"{}\"", os);
+    }
+
+    // Generate cfg values for version checks
+    // println!("cargo::rustc-check-cfg=cfg(nginx1_27_0)");
+    // println!("cargo::rerun-if-env-changed=DEP_NGINX_VERSION_NUMBER");
+    // if let Ok(version) = std::env::var("DEP_NGINX_VERSION_NUMBER") {
+    //     let version: u64 = version.parse().unwrap();
+    //
+    //     if version >= 1_027_000 {
+    //         println!("cargo::rustc-cfg=nginx1_27_0");
+    //     }
+    // }
+}

build.rs

@@ -8,8 +8,13 @@ homepage.workspace = true
 repository.workspace = true
 rust-version.workspace = true
 
-[dev-dependencies]
+build = "../build.rs"
+
+[dependencies]
+nginx-sys = { path = "../nginx-sys/", default-features = false }
 ngx = { path = "../", default-features = false }
+
+[dev-dependencies]
 aws-sign-v4 = "0.3.0"
 chrono = "0.4.23"
 http = "1.1.0"
@@ -42,8 +47,6 @@ name = "async"
 path = "async.rs"
 crate-type = ["cdylib"]
 
-[dependencies]
-
 [features]
 default = ["export-modules", "ngx/vendored"]
 # Generate `ngx_modules` table with module exports

examples/Cargo.toml

@@ -0,0 +1,23 @@
+use ngx::ffi;
+
+#[test]
+fn test_os_symbols() {
+    #[cfg(ngx_os = "freebsd")]
+    assert_eq!(ffi::NGX_FREEBSD, 1);
+
+    #[cfg(ngx_os = "linux")]
+    assert_eq!(ffi::NGX_LINUX, 1);
+
+    #[cfg(ngx_os = "darwin")]
+    assert_eq!(ffi::NGX_DARWIN, 1);
+}
+
+#[test]
+fn test_feature_symbols() {
+    let ev: ffi::ngx_event_t = unsafe { std::mem::zeroed() };
+
+    assert_eq!(ev.available, 0);
+
+    #[cfg(ngx_feature = "have_kqueue")]
+    assert_eq!(ev.kq_errno, 0);
+}