Update xUnit to display output on failures (#8147)

Modify the XCTest xUnit failure message to display the test result.

### Motivation:

The generated xUnit XML file is not helpful when tests fail as it
contains the message "failure", which is redundant with the test
results.

### Modifications:

Update the XML output to display the result output instead of static
"failure" message. The failure message may contain irrelevant output,
but it's better than the current message of `failure`.

### Result:

```
swift test 
```

Requires: swiftlang/swift#78300

---------

Co-authored-by: Jonathan Grynspan <grynspan@me.com>

Author: bkhouri

Fixtures/Miscellaneous/TestMultipleFailureSwiftTesting/Package.swift

@@ -0,0 +1,13 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "TestMultipleFailureSwiftTesting",
+    targets: [
+        .testTarget(
+            name: "TestMultipleFailureSwiftTestingTests"
+        )
+    ]
+)

Fixtures/Miscellaneous/TestMultipleFailureSwiftTesting/Tests/TestMultipleFailureSwiftTestingTests/TestMultipleFailureSwiftTestingTests.swift

@@ -0,0 +1,41 @@
+import Testing
+
+@Test func testFailure1() async throws {
+    #expect(Bool(false), "ST Test failure 1")
+}
+
+@Test func testFailure2() async throws {
+    #expect(Bool(false), "ST Test failure 2")
+}
+
+@Test func testFailure3() async throws {
+    #expect(Bool(false), "ST Test failure 3")
+}
+
+@Test func testFailure4() async throws {
+    #expect(Bool(false), "ST Test failure 4")
+}
+
+@Test func testFailure5() async throws {
+    #expect(Bool(false), "ST Test failure 5")
+}
+
+@Test func testFailure6() async throws {
+    #expect(Bool(false), "ST Test failure 6")
+}
+
+@Test func testFailure7() async throws {
+    #expect(Bool(false), "ST Test failure 7")
+}
+
+@Test func testFailure8() async throws {
+    #expect(Bool(false), "ST Test failure 8")
+}
+
+@Test func testFailure9() async throws {
+    #expect(Bool(false), "ST Test failure 9")
+}
+
+@Test func testFailure10() async throws {
+    #expect(Bool(false), "ST Test failure 10")
+}

Fixtures/Miscellaneous/TestMultipleFailureXCTest/Package.swift

@@ -0,0 +1,13 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "TestMultipleFailureXCTest",
+    targets: [
+        .testTarget(
+            name: "TestMultipleFailureXCTestTests"
+        )
+    ]
+)

Fixtures/Miscellaneous/TestMultipleFailureXCTest/Tests/TestMultipleFailureXCTestTests/TestMultipleFailureXCTestTests.swift

@@ -0,0 +1,44 @@
+import XCTest
+
+final class TestMultipleFailureXCTestTests: XCTestCase {
+    func testFailure1() throws {
+        XCTAssertFalse(true, "Test failure 1")
+    }
+
+    func testFailure2() throws {
+        XCTAssertFalse(true, "Test failure 2")
+    }
+
+    func testFailure3() throws {
+        XCTAssertFalse(true, "Test failure 3")
+    }
+
+    func testFailure4() throws {
+        XCTAssertFalse(true, "Test failure 4")
+    }
+
+    func testFailure5() throws {
+        XCTAssertFalse(true, "Test failure 5")
+    }
+
+    func testFailure6() throws {
+        XCTAssertFalse(true, "Test failure 6")
+    }
+
+    func testFailure7() throws {
+        XCTAssertFalse(true, "Test failure 7")
+    }
+
+    func testFailure8() throws {
+        XCTAssertFalse(true, "Test failure 8")
+    }
+
+    func testFailure9() throws {
+        XCTAssertFalse(true, "Test failure 9")
+    }
+
+    func testFailure10() throws {
+        XCTAssertFalse(true, "Test failure 10")
+    }
+
+}

Fixtures/Miscellaneous/TestSingleFailureSwiftTesting/Package.swift

@@ -0,0 +1,13 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "TestFailuresSwiftTesting",
+    targets: [
+        .testTarget(
+            name: "TestFailuresSwiftTestingTests"
+        )
+    ]
+)

Fixtures/Miscellaneous/TestSingleFailureSwiftTesting/Tests/TestFailuresSwiftTestingTests/TestFailuresSwiftTestingTests.swift

@@ -0,0 +1,5 @@
+import Testing
+
+@Test func example() async throws {
+    #expect(Bool(false), "Purposely failing & validating XML espace \"'<>")
+}

Fixtures/Miscellaneous/TestSingleFailureXCTest/Package.swift

@@ -0,0 +1,13 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "TestFailures",
+    targets: [
+        .testTarget(
+            name: "TestFailuresTests"
+        )
+    ]
+)

Fixtures/Miscellaneous/TestSingleFailureXCTest/Tests/TestFailuresTests/TestFailuresTests.swift

@@ -0,0 +1,8 @@
+import XCTest
+
+final class TestFailuresTests: XCTestCase {
+    func testExample() throws {
+        XCTAssertFalse(true, "Purposely failing & validating XML espace \"'<>")
+    }
+}
+

Sources/Commands/SwiftTestCommand.swift

@@ -188,6 +188,15 @@ struct TestCommandOptions: ParsableArguments {
             help: "Path where the xUnit xml file should be generated.")
     var xUnitOutput: AbsolutePath?
 
+    @Flag(
+        name: .customLong("experimental-xunit-message-failure"),
+        help: ArgumentHelp(
+            "When set, include the content of stdout/stderr in failure messages (XCTest only, experimental).",
+            visibility: .hidden
+        )
+    )
+    var shouldShowDetailedFailureMessage: Bool = false
+
     /// Generate LinuxMain entries and exit.
     @Flag(name: .customLong("testable-imports"), inversion: .prefixedEnableDisable, help: "Enable or disable testable imports. Enabled by default.")
     var enableTestableImports: Bool = true
@@ -416,7 +425,10 @@ public struct SwiftTestCommand: AsyncSwiftCommand {
             fileSystem: swiftCommandState.fileSystem,
             results: testResults
         )
-        try generator.generate(at: xUnitOutput)
+        try generator.generate(
+            at: xUnitOutput,
+            detailedFailureMessage: self.options.shouldShowDetailedFailureMessage
+        )
     }
 
     // MARK: - Common implementation
@@ -1379,7 +1391,7 @@ final class XUnitGenerator {
     }
 
     /// Generate the file at the given path.
-    func generate(at path: AbsolutePath) throws {
+    func generate(at path: AbsolutePath, detailedFailureMessage: Bool) throws {
         var content =
             """
             <?xml version="1.0" encoding="UTF-8"?>
@@ -1412,7 +1424,8 @@ final class XUnitGenerator {
                 """
 
             if !result.success {
-                content += "<failure message=\"failed\"></failure>\n"
+                let failureMessage = detailedFailureMessage ? result.output.map(_escapeForXML).joined() : "failure"
+                content += "<failure message=\"\(failureMessage)\"></failure>\n"
             }
 
             content += "</testcase>\n"
@@ -1429,6 +1442,32 @@ final class XUnitGenerator {
     }
 }
 
+/// Escape a single Unicode character for use in an XML-encoded string.
+///
+/// - Parameters:
+///   - character: The character to escape.
+///
+/// - Returns: `character`, or a string containing its escaped form.
+private func _escapeForXML(_ character: Character) -> String {
+    switch character {
+    case "\"":
+        "&quot;"
+    case "<":
+        "&lt;"
+    case ">":
+        "&gt;"
+    case "&":
+        "&amp;"
+    case _ where !character.isASCII || character.isNewline:
+    character.unicodeScalars.lazy
+        .map(\.value)
+        .map { "&#\($0);" }
+        .joined()
+    default:
+    String(character)
+    }
+}
+
 extension SwiftCommandState {
     func buildParametersForTest(
         options: TestCommandOptions

Sources/_InternalTestSupport/SwiftPMProduct.swift

@@ -76,13 +76,15 @@ extension SwiftPM {
     ///         - args: The arguments to pass.
     ///         - env: Additional environment variables to pass. The values here are merged with default env.
     ///         - packagePath: Adds argument `--package-path <path>` if not nil.
+    ///         - throwIfCommandFails: If set, will throw an error if the command does not have a 0 return code.
     ///
     /// - Returns: The output of the process.
     @discardableResult
     public func execute(
         _ args: [String] = [],
         packagePath: AbsolutePath? = nil,
-        env: Environment? = nil
+        env: Environment? = nil,
+        throwIfCommandFails: Bool = true
     ) async throws -> (stdout: String, stderr: String) {
         let result = try await executeProcess(
             args,
@@ -93,8 +95,11 @@ extension SwiftPM {
         let stdout = try result.utf8Output()
         let stderr = try result.utf8stderrOutput()
 
+        let returnValue = (stdout: stdout, stderr: stderr)
+        if (!throwIfCommandFails) { return returnValue }
+
         if result.exitStatus == .terminated(code: 0) {
-            return (stdout: stdout, stderr: stderr)
+            return returnValue
         }
         throw SwiftPMError.executionFailure(
             underlying: AsyncProcessResult.Error.nonZeroExit(result),