Merge pull request #7 from slashmo/feature/empty-trace-state

Add TraceState.none to create empty state

Author: slashmo

Sources/W3CTraceContext/TraceState.swift

@@ -20,7 +20,7 @@
 public struct TraceState {
     typealias Storage = [(vendor: String, value: String)]
 
-    private var _storage = Storage()
+    private var _storage: Storage
 
     init(_ storage: Storage) {
         self._storage = storage
@@ -30,6 +30,13 @@ public struct TraceState {
     public static let headerName = "tracestate"
 }
 
+extension TraceState {
+    /// Creates an empty `TraceState`.
+    public static var none: TraceState {
+        .init([])
+    }
+}
+
 extension TraceState: Equatable {
     public static func == (lhs: Self, rhs: Self) -> Bool {
         guard lhs._storage.count == rhs._storage.count else { return false }
@@ -69,7 +76,10 @@ extension TraceState: RawRepresentable {
                 }
             }
 
-            guard !rest.isEmpty else { return }
+            guard !rest.isEmpty else {
+                self._storage = Storage()
+                return
+            }
 
             var vendor = ""
 

Tests/W3CTraceContextTests/TraceStateTests.swift

@@ -15,16 +15,29 @@
 import XCTest
 
 final class TraceStateTests: XCTestCase {
+    // MARK: - Creation
+
+    func test_create_empty_trace_state() {
+        XCTAssertEqual(TraceState.none.rawValue, "")
+    }
+
     // MARK: - Equality
 
-    func testNotEqualIfStorageCountDiffers() {
+    func test_equal_sameStorage() {
+        let lhs = TraceState([("rojo", "00f067aa0ba902b7"), ("congo", "t61rcWkgMzE")])
+        let rhs = TraceState([("rojo", "00f067aa0ba902b7"), ("congo", "t61rcWkgMzE")])
+
+        XCTAssertEqual(lhs, rhs)
+    }
+
+    func test_not_equal_storageCountDiffers() {
         let lhs = TraceState([("rojo", "00f067aa0ba902b7")])
         let rhs = TraceState([("rojo", "00f067aa0ba902b7"), ("congo", "t61rcWkgMzE")])
 
         XCTAssertNotEqual(lhs, rhs)
     }
 
-    func testNotEqualIfStorageOrderDiffers() {
+    func test_not_equal_storageOrderDiffers() {
         let lhs = TraceState([("congo", "t61rcWkgMzE"), ("rojo", "00f067aa0ba902b7")])
         let rhs = TraceState([("rojo", "00f067aa0ba902b7"), ("congo", "t61rcWkgMzE")])
 
@@ -53,31 +66,31 @@ final class TraceStateTests: XCTestCase {
 
     // MARK: - Decoding
 
-    func testInitValidRawValue() {
+    func testInitRawValueValidRawValue() {
         let traceState = TraceState(rawValue: "rojo=00f067aa0ba902b7,congo=t61rcWkgMzE")
 
         XCTAssertEqual(traceState, TraceState([("rojo", "00f067aa0ba902b7"), ("congo", "t61rcWkgMzE")]))
     }
 
-    func testInitWithMultitenantRawValue() {
+    func testInitRawValueWithMultitenantRawValue() {
         let traceState = TraceState(rawValue: "fw529a3039@dt=00f067aa0ba902b7")
 
         XCTAssertEqual(traceState, TraceState([("fw529a3039@dt", "00f067aa0ba902b7")]))
     }
 
-    func testInitWithInvalidCharacterInKey() {
+    func testInitRawValueWithInvalidCharacterInKey() {
         XCTAssertNil(TraceState(rawValue: "ROJO=00f067aa0ba902b7"))
     }
 
-    func testInitEmptyRawValue() {
+    func testInitRawValueEmptyRawValue() {
         XCTAssertEqual(TraceState(rawValue: ""), TraceState([]))
     }
 
-    func testInitWithTooLongKey() {
+    func testInitRawValueWithTooLongKey() {
         XCTAssertNil(TraceState(rawValue: String(repeating: "1", count: 257) + "=t61rcWkgMzE"))
     }
 
-    func testInitWithKeyEndingWithAtSign() {
+    func testInitRawValueWithKeyEndingWithAtSign() {
         XCTAssertNil(TraceState(rawValue: "rojo@=00f067aa0ba902b7"))
     }
 
@@ -103,7 +116,7 @@ final class TraceStateTests: XCTestCase {
         ]))
     }
 
-    func testInitWhitespaceOnly() {
+    func testInitRawValueWhitespaceOnly() {
         XCTAssertEqual(TraceState(rawValue: "\t\t\t   "), TraceState([]))
     }
 }