[SR-5643] Add XCTPeformanceMetric string enum.

In Xcode 9, the XCTPerformanceMetric_WallClockTime string constant was
turned into a string enumeration to improve the ability to use strong typing
at call sites using it. At the same time, the defaultPerformanceMetrics class
function on XCTestCase was changed to be a class property.

Author: briancroom

Sources/XCTest/Public/XCTestCase+Performance.swift

@@ -11,8 +11,30 @@
 //  Methods on XCTestCase for testing the performance of code blocks.
 //
 
-/// Records wall clock time in seconds between `startMeasuring`/`stopMeasuring`.
-public let XCTPerformanceMetric_WallClockTime = WallClockTimeMetric.name
+public struct XCTPerformanceMetric : RawRepresentable, Equatable, Hashable {
+    public private(set) var rawValue: String
+
+    public init(_ rawValue: String) {
+        self.rawValue = rawValue
+    }
+
+    public init(rawValue: String) {
+        self.rawValue = rawValue
+    }
+
+    public var hashValue: Int {
+        return rawValue.hashValue
+    }
+
+    public static func ==(_ lhs: XCTPerformanceMetric, _ rhs: XCTPerformanceMetric) -> Bool {
+        return lhs.rawValue == rhs.rawValue
+    }
+}
+
+public extension XCTPerformanceMetric {
+    /// Records wall clock time in seconds between `startMeasuring`/`stopMeasuring`.
+    public static let wallClockTime = XCTPerformanceMetric(rawValue: WallClockTimeMetric.name)
+}
 
 /// The following methods are called from within a test method to carry out 
 /// performance testing on blocks of code.
@@ -21,11 +43,11 @@ public extension XCTestCase {
     /// The names of the performance metrics to measure when invoking `measure(block:)`. 
     /// Returns `XCTPerformanceMetric_WallClockTime` by default. Subclasses can
     /// override this to change the behavior of `measure(block:)`
-    class func defaultPerformanceMetrics() -> [String] {
-        return [XCTPerformanceMetric_WallClockTime]
+    class var defaultPerformanceMetrics: [XCTPerformanceMetric] {
+        return [.wallClockTime]
     }
 
-    /// Call from a test method to measure resources (`defaultPerformanceMetrics()`)
+    /// Call from a test method to measure resources (`defaultPerformanceMetrics`)
     /// used by the block in the current process.
     ///
     ///     func testPerformanceOfMyFunction() {
@@ -50,7 +72,7 @@ public extension XCTestCase {
     ///   ensure compatibility of tests between swift-corelibs-xctest and Apple
     ///   XCTest, it is not recommended to pass explicit values for `file` and `line`.
     func measure(file: StaticString = #file, line: Int = #line, block: () -> Void) {
-        measureMetrics(type(of: self).defaultPerformanceMetrics(),
+        measureMetrics(type(of: self).defaultPerformanceMetrics,
                        automaticallyStartMeasuring: true,
                        file: file,
                        line: line,
@@ -66,7 +88,7 @@ public extension XCTestCase {
     /// may interfere the API will measure them separately.
     ///
     ///     func testMyFunction2_WallClockTime() {
-    ///         measureMetrics(type(of: self).defaultPerformanceMetrics(), automaticallyStartMeasuring: false) {
+    ///         measureMetrics(type(of: self).defaultPerformanceMetrics, automaticallyStartMeasuring: false) {
     ///
     ///             // Do setup work that needs to be done for every iteration but
     ///             // you don't want to measure before the call to `startMeasuring()`
@@ -103,12 +125,12 @@ public extension XCTestCase {
     ///   these methods are not exactly identical between these environments. To
     ///   ensure compatibility of tests between swift-corelibs-xctest and Apple
     ///   XCTest, it is not recommended to pass explicit values for `file` and `line`.
-    func measureMetrics(_ metrics: [String], automaticallyStartMeasuring: Bool, file: StaticString = #file, line: Int = #line, for block: () -> Void) {
+    func measureMetrics(_ metrics: [XCTPerformanceMetric], automaticallyStartMeasuring: Bool, file: StaticString = #file, line: Int = #line, for block: () -> Void) {
         guard _performanceMeter == nil else {
             return recordAPIViolation(description: "Can only record one set of metrics per test method.", file: file, line: line)
         }
 
-        PerformanceMeter.measureMetrics(metrics, delegate: self, file: file, line: line) { meter in
+        PerformanceMeter.measureMetrics(metrics.map({ $0.rawValue }), delegate: self, file: file, line: line) { meter in
             self._performanceMeter = meter
             if automaticallyStartMeasuring {
                 meter.startMeasuring(file: file, line: line)

Tests/Functional/Performance/Misuse/main.swift

@@ -21,20 +21,20 @@ class PerformanceMisuseTestCase: XCTestCase {
         // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMultipleInOneTest_fails : API violation - Can only record one set of metrics per test method.
         measure {}
         // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMultipleInOneTest_fails : API violation - Can only record one set of metrics per test method.
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: true) {}
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: true) {}
     }
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMultipleInOneTest_fails' failed \(\d+\.\d+ seconds\)
 
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMetricsAndNotStartingOrEnding_fails' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     func test_whenMeasuringMetricsAndNotStartingOrEnding_fails() {
         // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMetricsAndNotStartingOrEnding_fails : API violation - startMeasuring\(\) must be called during the block.
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {}
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {}
     }
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMetricsAndNotStartingOrEnding_fails' failed \(\d+\.\d+ seconds\)
 
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStoppingWithoutStarting_fails' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     func test_whenMeasuringMetricsAndStoppingWithoutStarting_fails() {
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
             // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStoppingWithoutStarting_fails : API violation - Cannot stop measuring before starting measuring.
             self.stopMeasuring()
         }
@@ -43,7 +43,7 @@ class PerformanceMisuseTestCase: XCTestCase {
 
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStartingTwice_fails' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     func test_whenMeasuringMetricsAndStartingTwice_fails() {
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
             self.startMeasuring()
             // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStartingTwice_fails : API violation - Already called startMeasuring\(\) once this iteration.
             self.startMeasuring()
@@ -53,7 +53,7 @@ class PerformanceMisuseTestCase: XCTestCase {
 
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStoppingTwice_fails' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     func test_whenMeasuringMetricsAndStoppingTwice_fails() {
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
             self.startMeasuring()
             self.stopMeasuring()
             // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_whenMeasuringMetricsAndStoppingTwice_fails : API violation - Already called stopMeasuring\(\) once this iteration.
@@ -104,7 +104,7 @@ class PerformanceMisuseTestCase: XCTestCase {
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_measuringUnknownMetric_fails' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     func test_measuringUnknownMetric_fails() {
         // CHECK: .*/Misuse/main.swift:[[@LINE+1]]: error: PerformanceMisuseTestCase.test_measuringUnknownMetric_fails : API violation - Unknown metric: UnladenAirspeedVelocity
-        measureMetrics(["UnladenAirspeedVelocity"], automaticallyStartMeasuring: true) {}
+        measureMetrics([XCTPerformanceMetric("UnladenAirspeedVelocity")], automaticallyStartMeasuring: true) {}
     }
     // CHECK: Test Case 'PerformanceMisuseTestCase.test_measuringUnknownMetric_fails' failed \(\d+\.\d+ seconds\)
 

Tests/Functional/Performance/main.swift

@@ -30,7 +30,7 @@ class PerformanceTestCase: XCTestCase {
     // CHECK: Test Case 'PerformanceTestCase.test_measuresMetricsWithAutomaticStartAndStop' passed \(\d+\.\d+ seconds\)
     func test_measuresMetricsWithAutomaticStartAndStop() {
         var iterationCount = 0
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: true, for: {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: true, for: {
             iterationCount += 1
         })
         XCTAssertEqual(iterationCount, 10)
@@ -40,7 +40,7 @@ class PerformanceTestCase: XCTestCase {
     // CHECK: .*/Performance/main.swift:[[@LINE+3]]: Test Case 'PerformanceTestCase.test_measuresMetricsWithManualStartAndStop' measured \[Time, seconds\] .*
     // CHECK: Test Case 'PerformanceTestCase.test_measuresMetricsWithManualStartAndStop' passed \(\d+\.\d+ seconds\)
     func test_measuresMetricsWithManualStartAndStop() {
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
             self.startMeasuring()
             self.stopMeasuring()
         }
@@ -50,15 +50,15 @@ class PerformanceTestCase: XCTestCase {
     // CHECK: .*/Performance/main.swift:[[@LINE+3]]: Test Case 'PerformanceTestCase.test_measuresMetricsWithoutExplicitStop' measured \[Time, seconds\] .*
     // CHECK: Test Case 'PerformanceTestCase.test_measuresMetricsWithoutExplicitStop' passed \(\d+\.\d+ seconds\)
     func test_measuresMetricsWithoutExplicitStop() {
-        measureMetrics([XCTPerformanceMetric_WallClockTime], automaticallyStartMeasuring: false) {
+        measureMetrics([.wallClockTime], automaticallyStartMeasuring: false) {
             self.startMeasuring()
         }
     }
 
     // CHECK: Test Case 'PerformanceTestCase.test_hasWallClockAsDefaultPerformanceMetric' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+
     // CHECK: Test Case 'PerformanceTestCase.test_hasWallClockAsDefaultPerformanceMetric' passed \(\d+\.\d+ seconds\)
     func test_hasWallClockAsDefaultPerformanceMetric() {
-        XCTAssertEqual(PerformanceTestCase.defaultPerformanceMetrics(), [XCTPerformanceMetric_WallClockTime])
+        XCTAssertEqual(PerformanceTestCase.defaultPerformanceMetrics, [.wallClockTime])
     }
 
     // CHECK: Test Case 'PerformanceTestCase.test_printsValuesAfterMeasuring' started at \d+-\d+-\d+ \d+:\d+:\d+\.\d+