Add runtimeWarn() as public function (#51)

* Add runtimeWarn() as public function

Unfortunately without XCTest support

* fix failing tests by hard-coding the language to english

FoundationExtensions-Package.xctestplan

@@ -0,0 +1,24 @@
+{
+  "configurations" : [
+    {
+      "id" : "C7A8428F-1827-4A1D-9DEC-D6E40D9EAFEE",
+      "name" : "Test Scheme Action",
+      "options" : {
+        "language" : "en"
+      }
+    }
+  ],
+  "defaultOptions" : {
+
+  },
+  "testTargets" : [
+    {
+      "target" : {
+        "containerPath" : "container:",
+        "identifier" : "FoundationExtensionsTests",
+        "name" : "FoundationExtensionsTests"
+      }
+    }
+  ],
+  "version" : 1
+}

Package.swift

@@ -3,15 +3,29 @@ import PackageDescription
 
 let package = Package(
     name: "FoundationExtensions",
-    platforms: [.iOS(.v12), .macOS(.v10_15), .tvOS(.v13), .watchOS(.v6)],
+    platforms: [.iOS(.v13), .macOS(.v10_15), .tvOS(.v13), .watchOS(.v6)],
     products: [
         .library(name: "FoundationExtensions", targets: ["FoundationExtensions"]),
         .library(name: "FoundationExtensionsDynamic", type: .dynamic, targets: ["FoundationExtensions"])
     ],
-    dependencies: [],
+    dependencies: [
+    ],
     targets: [
-        .target(name: "FoundationExtensions", dependencies: []),
-        .target(name: "FoundationExtensionsDynamic", dependencies: []),
-        .testTarget(name: "FoundationExtensionsTests", dependencies: ["FoundationExtensions"])
+        .target(
+            name: "FoundationExtensions",
+            dependencies: [
+            ]
+        ),
+        .target(
+            name: "FoundationExtensionsDynamic",
+            dependencies: [
+            ]
+        ),
+        .testTarget(
+            name: "FoundationExtensionsTests",
+            dependencies: [
+                "FoundationExtensions"
+            ]
+        )
     ]
 )

Sources/FoundationExtensions/Runtime/RuntimeWarning.swift

@@ -0,0 +1,76 @@
+// Copyright (c) 2021 Point-Free, Inc.
+//
+// RuntimeWarning adopted from from https://www.pointfree.co/blog/posts/70-unobtrusive-runtime-warnings-for-libraries and
+// https://github.com/pointfreeco/swift-composable-architecture/blob/main/Sources/ComposableArchitecture/Internal/RuntimeWarnings.swift
+
+import Foundation
+
+extension Notification.Name {
+  public static let foundationExtensionsRuntimeWarning = Self("FoundationExtensions.runtimeWarning")
+}
+
+@_transparent
+@inline(__always)
+public func runtimeWarning(
+  _ message: @autoclosure () -> String,
+  category: String? = "FoundationExtensions"
+) {
+  #if DEBUG
+    let message = message()
+    NotificationCenter.default.post(
+      name: .foundationExtensionsRuntimeWarning,
+      object: nil,
+      userInfo: ["message": message]
+    )
+    let category = category ?? "Runtime Warning"
+    #if canImport(os)
+      os_log(
+        .fault,
+        dso: dso,
+        log: OSLog(subsystem: "com.apple.runtime-issues", category: category),
+        "%@",
+        message
+      )
+    #else
+      fputs("\(formatter.string(from: Date())) [\(category)] \(message)\n", stderr)
+    #endif
+  #endif
+}
+
+
+#if DEBUG
+
+  #if canImport(os)
+    import os
+
+    // NB: Xcode runtime warnings offer a much better experience than traditional assertions and
+    //     breakpoints, but Apple provides no means of creating custom runtime warnings ourselves.
+    //     To work around this, we hook into SwiftUI's runtime issue delivery mechanism, instead.
+    //
+    // Feedback filed: https://gist.github.com/stephencelis/a8d06383ed6ccde3e5ef5d1b3ad52bbc
+    @usableFromInline
+    let dso = { () -> UnsafeMutableRawPointer in
+      let count = _dyld_image_count()
+      for i in 0..<count {
+        if let name = _dyld_get_image_name(i) {
+          let swiftString = String(cString: name)
+          if swiftString.hasSuffix("/SwiftUI") {
+            if let header = _dyld_get_image_header(i) {
+              return UnsafeMutableRawPointer(mutating: UnsafeRawPointer(header))
+            }
+          }
+        }
+      }
+      return UnsafeMutableRawPointer(mutating: #dsohandle)
+    }()
+  #else
+    import Foundation
+
+    @usableFromInline
+    let formatter: DateFormatter = {
+      let formatter = DateFormatter()
+      formatter.dateFormat = "yyyy-MM-dd HH:MM:SS.sssZ"
+      return formatter
+    }()
+  #endif
+#endif