Bump ABI.CurrentVersion to 6.3 and ensure minor variances in JSON version numbers are permitted. (#1438)

This PR ensures that the JSON schema version 6.3 is considered
"supported" in Swift Testing 6.3. As well, it suppresses a thrown error
when the `version` field of a JSON record is slightly higher than the
expected schema. For example, if we ask Swift Testing the ABI version
corresponding to `VersionNumber(6, 3, 1)`, we'll get back `v6_3`, but
then if we try to decode a JSON record whose `version` field equals
`"6.3.1"`, we'll throw a version mismatch error. This error is now
suppressed unless the versions really do mismatch.

### 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.

---------

Co-authored-by: Stuart Montgomery <[email protected]>

Author: grynspan

Sources/Testing/ABI/ABI.Record.swift

@@ -70,15 +70,26 @@ extension ABI.Record: Codable {
   init(from decoder: any Decoder) throws {
     let container = try decoder.container(keyedBy: CodingKeys.self)
 
-    let versionNumber = try container.decode(VersionNumber.self, forKey: .version)
-    if versionNumber != V.versionNumber {
+    func validateVersionNumber(_ versionNumber: VersionNumber) throws {
+      if versionNumber == V.versionNumber {
+        return
+      }
+#if !hasFeature(Embedded)
+      // Allow for alternate version numbers if they correspond to the expected
+      // record version (e.g. "1.2.3" might map to `v1_2_0` without a problem.)
+      if ABI.version(forVersionNumber: versionNumber) == V.self {
+        return
+      }
+#endif
       throw DecodingError.dataCorrupted(
         DecodingError.Context(
           codingPath: decoder.codingPath + CollectionOfOne(CodingKeys.version as any CodingKey),
           debugDescription: "Unexpected record version \(versionNumber) (expected \(V.versionNumber))."
         )
       )
     }
+    let versionNumber = try container.decode(VersionNumber.self, forKey: .version)
+    try validateVersionNumber(versionNumber)
 
     switch try container.decode(String.self, forKey: .kind) {
     case "test":

Sources/Testing/ABI/ABI.swift

@@ -43,7 +43,7 @@ extension ABI {
   }
 
   /// The current supported ABI version (ignoring any experimental versions.)
-  typealias CurrentVersion = v0
+  typealias CurrentVersion = v6_3
 
   /// The highest defined and supported ABI version (including any experimental
   /// versions.)
@@ -55,10 +55,18 @@ extension ABI {
   /// - Parameters:
   ///   - versionNumber: The ABI version number for which a concrete type is
   ///     needed.
+  ///   - swiftCompilerVersion: The version number of the Swift compiler. This
+  ///     is used when `versionNumber` is greater than the highest known version
+  ///     to determine whether a version type can be returned. The default value
+  ///     is the version of the Swift compiler which was used to build the
+  ///     testing library.
   ///
   /// - Returns: A type conforming to ``ABI/Version`` that represents the given
   ///   ABI version, or `nil` if no such type exists.
-  static func version(forVersionNumber versionNumber: VersionNumber = ABI.CurrentVersion.versionNumber) -> (any Version.Type)? {
+  static func version(
+    forVersionNumber versionNumber: VersionNumber,
+    givenSwiftCompilerVersion swiftCompilerVersion: @autoclosure () -> VersionNumber = swiftCompilerVersion
+  ) -> (any Version.Type)? {
     if versionNumber > ABI.HighestVersion.versionNumber {
       // If the caller requested an ABI version higher than the current Swift
       // compiler version and it's not an ABI version we've explicitly defined,
@@ -71,7 +79,7 @@ extension ABI {
       // Note also that building an old version of Swift Testing with a newer
       // compiler may produce incorrect results here. We don't generally support
       // that configuration though.
-      if versionNumber > swiftCompilerVersion {
+      if versionNumber > swiftCompilerVersion() {
         return nil
       }
     }

Tests/TestingTests/SwiftPMTests.swift

@@ -302,10 +302,11 @@ struct SwiftPMTests {
 
   @Test("New-but-not-experimental ABI version")
   func newButNotExperimentalABIVersion() async throws {
-    var versionNumber = ABI.CurrentVersion.versionNumber
-    versionNumber.patchComponent += 1
-    let version = try #require(ABI.version(forVersionNumber: versionNumber))
-    #expect(version.versionNumber == ABI.v0.versionNumber)
+    let currentVersionNumber = ABI.CurrentVersion.versionNumber
+    var newerVersionNumber = currentVersionNumber
+    newerVersionNumber.patchComponent += 1
+    let version = try #require(ABI.version(forVersionNumber: newerVersionNumber, givenSwiftCompilerVersion: newerVersionNumber))
+    #expect(version.versionNumber == currentVersionNumber)
   }
 
   @Test("Unsupported ABI version")