Add XCTUnimplemented (#16)

Author: stephencelis

Makefile

@@ -1,11 +1,12 @@
+# NB: We can't rely on `XCTExpectFailure` because it doesn't exist in `swift-corelibs-foundation`
 PASS = \033[1;7;32m PASS \033[0m
 FAIL = \033[1;7;31m FAIL \033[0m
 XCT_FAIL = \033[34mXCTFail\033[0m
 EXPECTED_STRING = This is expected to fail!
 EXPECTED = \033[31m\"$(EXPECTED_STRING)\"\033[0m
 
 test:
-	@swift test --enable-test-discovery 2>&1 | grep '$(EXPECTED_STRING)' > /dev/null \
+	@swift test 2>&1 | grep '$(EXPECTED_STRING)' > /dev/null \
 		&& (echo "$(PASS) $(XCT_FAIL) was called with $(EXPECTED)" && exit) \
 		|| (echo "$(FAIL) expected $(XCT_FAIL) to be called with $(EXPECTED)" >&2 && exit 1)
 
@@ -14,7 +15,7 @@ test-linux:
 		--rm \
 		-v "$(PWD):$(PWD)" \
 		-w "$(PWD)" \
-		swift:5.3 \
+		swift:5.6.2-focal \
 		bash -c "make test"
 
 format:

Package.swift

@@ -1,9 +1,15 @@
-// swift-tools-version:5.1
+// swift-tools-version:5.5
 
 import PackageDescription
 
 let package = Package(
   name: "xctest-dynamic-overlay",
+  platforms: [
+    .iOS(.v13),
+    .macOS(.v10_15),
+    .tvOS(.v13),
+    .watchOS(.v6),
+  ],
   products: [
     .library(name: "XCTestDynamicOverlay", targets: ["XCTestDynamicOverlay"])
   ],

Sources/XCTestDynamicOverlay/Internal/Breakpoint.swift

@@ -0,0 +1,44 @@
+#if DEBUG && 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
+  private let rw = (
+    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)
+    }(),
+    log: OSLog(subsystem: "com.apple.runtime-issues", category: "XCTestDynamicOverlay")
+  )
+#endif
+
+@_transparent
+@inline(__always)
+func runtimeWarning(
+  _ message: @autoclosure () -> StaticString,
+  _ args: @autoclosure () -> [CVarArg] = []
+) {
+  #if DEBUG && canImport(os)
+    let message = message()
+    if !_XCTIsTesting {
+      unsafeBitCast(
+        os_log as (OSLogType, UnsafeRawPointer, OSLog, StaticString, CVarArg...) -> Void,
+        to: ((OSLogType, UnsafeRawPointer, OSLog, StaticString, [CVarArg]) -> Void).self
+      )(.fault, rw.dso, rw.log, message, args())
+    }
+    XCTFail(String(format: "\(message)", arguments: args()))
+  #endif
+}

Sources/XCTestDynamicOverlay/Internal/RuntimeWarnings.swift

@@ -0,0 +1,31 @@
+#if DEBUG
+  #if canImport(ObjectiveC)
+    import Foundation
+
+    var XCTCurrentTestCase: AnyObject? {
+      guard
+        let XCTestObservationCenter = NSClassFromString("XCTestObservationCenter")
+        as Any as? NSObjectProtocol,
+        String(describing: XCTestObservationCenter) != "<null>",
+        let shared = XCTestObservationCenter.perform(Selector(("sharedTestObservationCenter")))?
+          .takeUnretainedValue(),
+        let observers = shared.perform(Selector(("observers")))?
+          .takeUnretainedValue() as? [AnyObject],
+        let observer =
+        observers
+          .first(where: { NSStringFromClass(type(of: $0)) == "XCTestMisuseObserver" }),
+        let currentTestCase = observer.perform(Selector(("currentTestCase")))?
+          .takeUnretainedValue()
+      else { return nil }
+      return currentTestCase
+    }
+  #else
+    var XCTCurrentTestCase: AnyObject? {
+      nil
+    }
+  #endif
+#else
+  var XCTCurrentTestCase: AnyObject? {
+    nil
+  }
+#endif

Sources/XCTestDynamicOverlay/Internal/XCTCurrentTestCase.swift

@@ -12,18 +12,7 @@
     ///   results.
     public func XCTFail(_ message: String = "") {
       guard
-        let XCTestObservationCenter = NSClassFromString("XCTestObservationCenter")
-          as Any as? NSObjectProtocol,
-        String(describing: XCTestObservationCenter) != "<null>",
-        let shared = XCTestObservationCenter.perform(Selector(("sharedTestObservationCenter")))?
-          .takeUnretainedValue(),
-        let observers = shared.perform(Selector(("observers")))?
-          .takeUnretainedValue() as? [AnyObject],
-        let observer =
-          observers
-          .first(where: { NSStringFromClass(type(of: $0)) == "XCTestMisuseObserver" }),
-        let currentTestCase = observer.perform(Selector(("currentTestCase")))?
-          .takeUnretainedValue(),
+        let currentTestCase = XCTCurrentTestCase,
         let XCTIssue = NSClassFromString("XCTIssue")
           as Any as? NSObjectProtocol,
         let alloc = XCTIssue.perform(NSSelectorFromString("alloc"))?
@@ -37,28 +26,23 @@
           )?
           .takeUnretainedValue()
       else {
-        #if canImport(Darwin)
-          let indentedMessage = message.split(separator: "\n", omittingEmptySubsequences: false)
-            .map { "  \($0)" }
-            .joined(separator: "\n")
+        runtimeWarning(
+          """
+          "XCTFail" was invoked outside of a test.
 
-          breakpoint(
-            """
-            ---
-            Warning: "XCTestDynamicOverlay.XCTFail" has been invoked outside of tests\
-            \(message.isEmpty ? "." : "with the message:\n\n\(indentedMessage)")
+            Message:
+              %@
 
-            This function should only be invoked during an XCTest run, and is a no-op when run in \
-            application code. If you or a library you depend on is using "XCTFail" for \
-            test-specific code paths, ensure that these same paths are not called in your \
-            application.
-            ---
-            """
-          )
-        #endif
+          This function should only be invoked during an XCTest run, and is a no-op when run in \
+          application code. If you or a library you depend on is using "XCTFail" for test-specific \
+          code paths, ensure that these same paths are not called in your application.
+          """,
+          [
+            message.isEmpty ? "(none)" : message
+          ]
+        )
         return
       }
-
       _ = currentTestCase.perform(Selector(("recordIssue:")), with: issue)
     }
 

Sources/XCTestDynamicOverlay/XCTFail.swift

@@ -0,0 +1,9 @@
+import Foundation
+
+public let _XCTIsTesting: Bool = {
+  guard let path = ProcessInfo.processInfo.arguments.first
+  else { return false }
+
+  let url = URL(fileURLWithPath: path)
+  return url.lastPathComponent == "xctest" || url.pathExtension == "xctest"
+}()