Don't hard-code numeric representations of ABI versions. (#968)

This PR replaces some hard-coded ABI version numbers (`-1`, `0`, and
`1`) with symbolic references. It also removes a common code path
between the Xcode 16-compatible C entry point and the formal "v0"
one so that deleting the Xcode 16 legacy paths will be easier
later.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: grynspan

Sources/Testing/ABI/Encoded/ABI.EncodedTest.swift

@@ -98,7 +98,7 @@ extension ABI {
       sourceLocation = test.sourceLocation
       id = ID(encoding: test.id)
 
-      if V.versionNumber >= 1 {
+      if V.versionNumber >= ABI.v1.versionNumber {
         let tags = test.tags
         if !tags.isEmpty {
           _tags = tags.map(String.init(describing:))

Sources/Testing/ABI/EntryPoints/ABIEntryPoint.swift

@@ -47,10 +47,17 @@ extension ABI.v0 {
   /// callback.
   public static var entryPoint: EntryPoint {
     return { configurationJSON, recordHandler in
-      try await _entryPoint(
-        configurationJSON: configurationJSON,
-        recordHandler: recordHandler
-      ) == EXIT_SUCCESS
+      let args = try configurationJSON.map { configurationJSON in
+        try JSON.decode(__CommandLineArguments_v0.self, from: configurationJSON)
+      }
+      let eventHandler = try eventHandlerForStreamingEvents(version: args?.eventStreamVersion, encodeAsJSONLines: false, forwardingTo: recordHandler)
+
+      switch await Testing.entryPoint(passing: args, eventHandler: eventHandler) {
+      case EXIT_SUCCESS, EXIT_NO_TESTS_FOUND:
+        return true
+      default:
+        return false
+      }
     }
   }
 }
@@ -89,48 +96,21 @@ extension ABI.Xcode16 {
 @usableFromInline func copyABIEntryPoint_v0() -> UnsafeMutableRawPointer {
   let result = UnsafeMutablePointer<ABI.Xcode16.EntryPoint>.allocate(capacity: 1)
   result.initialize { configurationJSON, recordHandler in
-    try await _entryPoint(
-      configurationJSON: configurationJSON,
-      eventStreamVersionIfNil: -1,
-      recordHandler: recordHandler
-    )
+    var args = try configurationJSON.map { configurationJSON in
+      try JSON.decode(__CommandLineArguments_v0.self, from: configurationJSON)
+    }
+    if args?.eventStreamVersion == nil {
+      args?.eventStreamVersion = ABI.Xcode16.versionNumber
+    }
+    let eventHandler = try eventHandlerForStreamingEvents(version: args?.eventStreamVersion, encodeAsJSONLines: false, forwardingTo: recordHandler)
+
+    var exitCode = await Testing.entryPoint(passing: args, eventHandler: eventHandler)
+    if exitCode == EXIT_NO_TESTS_FOUND {
+      exitCode = EXIT_SUCCESS
+    }
+    return exitCode
   }
   return .init(result)
 }
 #endif
-
-// MARK: -
-
-/// A common implementation for ``ABI/v0/entryPoint-swift.type.property`` and
-/// ``copyABIEntryPoint_v0()`` that provides Xcode&nbsp;16 compatibility.
-///
-/// This function will be removed (with its logic incorporated into
-/// ``ABI/v0/entryPoint-swift.type.property``) in a future update.
-private func _entryPoint(
-  configurationJSON: UnsafeRawBufferPointer?,
-  eventStreamVersionIfNil: Int? = nil,
-  recordHandler: @escaping @Sendable (_ recordJSON: UnsafeRawBufferPointer) -> Void
-) async throws -> CInt {
-  var args = try configurationJSON.map { configurationJSON in
-    try JSON.decode(__CommandLineArguments_v0.self, from: configurationJSON)
-  }
-
-  // If the caller needs a nil event stream version to default to a specific
-  // JSON schema, apply it here as if they'd specified it in the configuration
-  // JSON blob.
-  if let eventStreamVersionIfNil, args?.eventStreamVersion == nil {
-    args?.eventStreamVersion = eventStreamVersionIfNil
-  }
-
-  let eventHandler = try eventHandlerForStreamingEvents(version: args?.eventStreamVersion, encodeAsJSONLines: false, forwardingTo: recordHandler)
-  let exitCode = await entryPoint(passing: args, eventHandler: eventHandler)
-
-  // To maintain compatibility with Xcode 16, suppress custom exit codes. (This
-  // is also needed by ABI.v0.entryPoint to correctly treat the no-tests as a
-  // successful run.)
-  if exitCode == EXIT_NO_TESTS_FOUND {
-    return EXIT_SUCCESS
-  }
-  return exitCode
-}
 #endif

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -632,14 +632,14 @@ func eventHandlerForStreamingEvents(
   case nil:
     eventHandler(for: ABI.CurrentVersion.self)
 #if !SWT_NO_SNAPSHOT_TYPES
-  case -1:
+  case ABI.Xcode16.versionNumber:
     // Legacy support for Xcode 16. Support for this undocumented version will
     // be removed in a future update. Do not use it.
     eventHandler(for: ABI.Xcode16.self)
 #endif
-  case 0:
+  case ABI.v0.versionNumber:
     eventHandler(for: ABI.v0.self)
-  case 1:
+  case ABI.v1.versionNumber:
     eventHandler(for: ABI.v1.self)
   case let .some(unsupportedVersionNumber):
     throw _EntryPointError.invalidArgument("--event-stream-version", value: "\(unsupportedVersionNumber)")

Tests/TestingTests/SwiftPMTests.swift

@@ -228,15 +228,15 @@ struct SwiftPMTests {
 
   @Test("--event-stream-output-path argument (writes to a stream and can be read back)",
         arguments: [
-          ("--event-stream-output-path", "--event-stream-version", 0),
-          ("--experimental-event-stream-output", "--experimental-event-stream-version", 0),
-          ("--experimental-event-stream-output", "--experimental-event-stream-version", 1),
+          ("--event-stream-output-path", "--event-stream-version", ABI.v0.versionNumber),
+          ("--experimental-event-stream-output", "--experimental-event-stream-version", ABI.v0.versionNumber),
+          ("--experimental-event-stream-output", "--experimental-event-stream-version", ABI.v1.versionNumber),
         ])
   func eventStreamOutput(outputArgumentName: String, versionArgumentName: String, version: Int) async throws {
     switch version {
-    case 0:
+    case ABI.v0.versionNumber:
       try await eventStreamOutput(outputArgumentName: outputArgumentName, versionArgumentName: versionArgumentName, version: ABI.v0.self)
-    case 1:
+    case ABI.v1.versionNumber:
       try await eventStreamOutput(outputArgumentName: outputArgumentName, versionArgumentName: versionArgumentName, version: ABI.v1.self)
     default:
       Issue.record("Unreachable event stream version \(version)")
@@ -282,7 +282,7 @@ struct SwiftPMTests {
     }
     #expect(testRecords.count == 1)
     for testRecord in testRecords {
-      if version.versionNumber >= 1 {
+      if version.versionNumber >= ABI.v1.versionNumber {
         #expect(testRecord._tags != nil)
       } else {
         #expect(testRecord._tags == nil)