#72-add-vcpkg-optional-dependency

add opt in dependency for vcpkg
make pkg-config optional but default

Cargo.toml

@@ -20,8 +20,12 @@ name = "libxml"
 [dependencies]
 libc = "0.2"
 
+[features]
+default = ["pkg-config"]
+
 [build-dependencies]
-pkg-config = "0.3.2"
+pkg-config = {version = "0.3.2", optional = true }
+vcpkg = { version = "0.2", optional = true }
 
 [dev-dependencies]
 rayon = "1.0.0"

build.rs

@@ -1,7 +1,44 @@
-use pkg_config::find_library;
+fn main() {  
+  if cfg!(not(feature = "pkg-config")) && cfg!(not(feature = "vcpkg"))
+  {
+    panic!(r#"Enable "pkg-config" or "vcpkg" feature flags to locate libxml2"#)
+  }
+
+  #[cfg(feature = "pkg-config")]
+  {
+    if pkg_config_dep::find() {
+      return;
+    }
+  }
 
-fn main() {
-  if find_library("libxml-2.0").is_err() {
-    panic!("Could not find libxml2 using pkg-config")
+  #[cfg(feature = "vcpkg")]
+  {
+    if vcpkg_dep::find() {
+      return;
+    } 
   }
+
+  panic!("Could not find libxml2.")
 }
+
+#[cfg(feature = "pkg-config")]
+mod pkg_config_dep {
+  use pkg_config;
+  pub fn find() -> bool {
+    if pkg_config::find_library("libxml-2.0").is_ok() {
+      return true;
+    }
+    false
+  }
+}
+
+#[cfg(feature = "vcpkg")]
+mod vcpkg_dep {
+  use vcpkg;
+  pub fn find() -> bool {
+    if vcpkg::find_package("libxml2").is_ok() {
+      return true
+    }
+    false
+  }
+}