Add sequence encoding support.

Author: lukeredpath

Sources/Coding/Encoding.swift

@@ -101,7 +101,7 @@ public extension Encoding where Value: Encodable {
     }
 
     static var unkeyed: Self {
-        Self { value, encoder in
+        .init { value, encoder in
             var container = encoder.unkeyedContainer()
             try container.encode(value)
         }
@@ -115,6 +115,17 @@ public extension Encoding where Value: Encodable {
     }
 }
 
+public extension Encoding where Value: Sequence, Value.Element: Encodable {
+    static func arrayOf(_ encoding: Encoding<Value.Element>) -> Self {
+        .init { value, encoder in
+            var container = encoder.unkeyedContainer()
+            for element in value {
+                try encoding.encode(element, container.superEncoder())
+            }
+        }
+    }
+}
+
 public extension Encoding {
     static var nullValue: Self {
         .init { _, encoder in

Tests/CodingTests/EncodingTests.swift

@@ -363,6 +363,24 @@ final class EncodingTests: XCTestCase {
         )
     }
 
+    //  MARK: - Collection Encoding
+
+    func testEncodeArrayWithCustomEncodingForEachValue() {
+        let strings = ["One", "Two", "Three"]
+
+        XCTAssertEqual(
+            "[\"One\",\"Two\",\"Three\"]",
+            stringValue(try encoder.encode(strings, as: .singleValue))
+        )
+
+        let uppercased: Encoding<String> = .singleValue.pullback { $0.uppercased() }
+
+        XCTAssertEqual(
+            "[\"ONE\",\"TWO\",\"THREE\"]",
+            stringValue(try encoder.encode(strings, as: .arrayOf(uppercased)))
+        )
+    }
+
     private func stringValue(_ data: Data) -> String {
         String(data: data, encoding: .utf8)!
     }