Add Dictionary.removeEmpty()

Sources/ProjectSpec/CollectionExtensions.swift

@@ -0,0 +1,33 @@
+import Foundation
+
+private protocol EmptyRemovable {
+    func removeEmpty() -> Self
+    var isEmpty: Bool { get }
+}
+
+extension Array: EmptyRemovable {
+    public func removeEmpty() -> Array {
+        return compactMap {
+            if let e = ($0 as? EmptyRemovable)?.removeEmpty() {
+                return e.isEmpty ? nil : e as? Element
+            }
+            return $0
+        }
+    }
+}
+
+extension Dictionary: EmptyRemovable {
+    // this is a little trick that defines the generics parameter from optional Value to unwrapped Value
+    private static func removeEmpty<Key, Value>(dict: Dictionary<Key, Value?>) -> Dictionary<Key, Value> {
+        return dict.compactMapValues {
+            if let e = ($0 as? EmptyRemovable)?.removeEmpty() {
+                return e.isEmpty ? nil : e as? Value
+            }
+            return $0
+        }
+    }
+
+    public func removeEmpty() -> Dictionary<Key, Value> {
+        return Dictionary.removeEmpty(dict: self)
+    }
+}