Merge pull request #221 from tsabirgaliev/master

Require `zlib` dependency only for non-Apple platforms

Package.swift

@@ -17,16 +17,30 @@
  */
 import PackageDescription
 
+var dependencies: [Package.Dependency] = [
+  .package(url: "https://github.com/apple/swift-protobuf.git", from: "1.0.2"),
+  .package(url: "https://github.com/kylef/Commander.git", from: "0.8.0")
+]
+
+/*
+ * `swift-nio-zlib-support` uses `pkgConfig` to find `zlib` on 
+ * non-Apple platforms. Details here: 
+ * https://github.com/apple/swift-nio-zlib-support/issues/2#issuecomment-384681975
+ * 
+ * This doesn't play well with Macports, so require it only for non-Apple
+ * platforms, until there is a better solution. 
+ * Issue: https://github.com/grpc/grpc-swift/issues/220
+ */
+#if !os(macOS)
+dependencies.append(.package(url: "https://github.com/apple/swift-nio-zlib-support.git", from: "1.0.0"))
+#endif
+
 let package = Package(
   name: "SwiftGRPC",
   products: [
     .library(name: "SwiftGRPC", targets: ["SwiftGRPC"]),
   ],
-  dependencies: [
-    .package(url: "https://github.com/apple/swift-nio-zlib-support.git", from: "1.0.0"),
-    .package(url: "https://github.com/apple/swift-protobuf.git", from: "1.0.2"),
-    .package(url: "https://github.com/kylef/Commander.git", from: "0.8.0")
-  ],
+  dependencies: dependencies,
   targets: [
     .target(name: "SwiftGRPC",
             dependencies: ["CgRPC", "SwiftProtobuf"]),