Remove legacy test content discovery.

This PR removes the legacy test content discovery mechanism that is based on
finding protocol conformances in the type metadata section emitted by the Swift
compiler.

Author: grynspan

Documentation/Porting.md

@@ -145,10 +145,6 @@ to load that information:
 +  let resourceName: Str255 = switch kind {
 +  case .testContent:
 +    "__swift5_tests"
-+#if !SWT_NO_LEGACY_TEST_DISCOVERY
-+  case .typeMetadata:
-+    "__swift5_types"
-+#endif
 +  }
 +
 +  let oldRefNum = CurResFile()
@@ -214,9 +210,8 @@ start with `"SWT_"`).
 If your platform does not support dynamic linking and loading, you will need to
 use static linkage instead. Define the `"SWT_NO_DYNAMIC_LINKING"` compiler
 conditional for your platform in both `Package.swift` and
-`CompilerSettings.cmake`, then define the symbols `_testContentSectionBegin`,
-`_testContentSectionEnd`, `_typeMetadataSectionBegin`, and
-`_typeMetadataSectionEnd` in `SectionBounds.swift`:
+`CompilerSettings.cmake`, then define the symbols `_testContentSectionBegin` and
+`_testContentSectionEnd` in `SectionBounds.swift`:
 
 ```diff
 --- a/Sources/_TestDiscovery/SectionBounds.swift
@@ -225,18 +220,10 @@ conditional for your platform in both `Package.swift` and
 +#elseif os(Classic)
 +@_silgen_name(raw: "...") private nonisolated(unsafe) var _testContentSectionBegin: _SectionBound
 +@_silgen_name(raw: "...") private nonisolated(unsafe) var _testContentSectionEnd: _SectionBound
-+#if !SWT_NO_LEGACY_TEST_DISCOVERY
-+@_silgen_name(raw: "...") private nonisolated(unsafe) var _typeMetadataSectionBegin: _SectionBound
-+@_silgen_name(raw: "...") private nonisolated(unsafe) var _typeMetadataSectionEnd: _SectionBound
-+#endif
  #else
  #warning("Platform-specific implementation missing: Runtime test discovery unavailable (static)")
  private nonisolated(unsafe) let _testContentSectionBegin = UnsafeMutableRawPointer.allocate(byteCount: 1, alignment: 16)
  private nonisolated(unsafe) let _testContentSectionEnd = _testContentSectionBegin
- #if !SWT_NO_LEGACY_TEST_DISCOVERY
- private nonisolated(unsafe) let _typeMetadataSectionBegin = UnsafeMutableRawPointer.allocate(byteCount: 1, alignment: 16)
- private nonisolated(unsafe) let _typeMetadataSectionEnd = _typeMetadataSectionBegin
- #endif
  #endif
  // ...
 ```

Sources/Testing/CMakeLists.txt

@@ -88,7 +88,6 @@ add_library(Testing
   Test.ID.swift
   Test.swift
   Test+Discovery.swift
-  Test+Discovery+Legacy.swift
   Test+Macro.swift
   Traits/Bug.swift
   Traits/Comment.swift

Sources/Testing/ExitTests/ExitTest.swift

@@ -296,15 +296,6 @@ extension ExitTest {
       }
     }
 
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-    // Call the legacy lookup function that discovers tests embedded in types.
-    for record in Self.allTypeMetadataBasedTestContentRecords() {
-      if let exitTest = record.load(withHint: id) {
-        return exitTest
-      }
-    }
-#endif
-
     return nil
   }
 }

Sources/Testing/Test+Discovery+Legacy.swift

@@ -61,47 +61,15 @@ extension Test {
       // defective test records.)
       var result = Set<Self>()
 
-      // Figure out which discovery mechanism to use. By default, we'll use both
-      // the legacy and new mechanisms, but we can set an environment variable
-      // to explicitly select one or the other. When we remove legacy support,
-      // we can also remove this enumeration and environment variable check.
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-      let (useNewMode, useLegacyMode) = switch Environment.flag(named: "SWT_USE_LEGACY_TEST_DISCOVERY") {
-      case .none:
-        (true, true)
-      case .some(true):
-        (false, true)
-      case .some(false):
-        (true, false)
-      }
-#else
-      let useNewMode = true
-#endif
-
       // Walk all test content and gather generator functions, then call them in
       // a task group and collate their results.
-      if useNewMode {
-        let generators = Generator.allTestContentRecords().lazy.compactMap { $0.load() }
-        await withTaskGroup(of: Self.self) { taskGroup in
-          for generator in generators {
-            taskGroup.addTask { await generator.rawValue() }
-          }
-          result = await taskGroup.reduce(into: result) { $0.insert($1) }
-        }
-      }
-
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-      // Perform legacy test discovery if needed.
-      if useLegacyMode && result.isEmpty {
-        let generators = Generator.allTypeMetadataBasedTestContentRecords().lazy.compactMap { $0.load() }
-        await withTaskGroup(of: Self.self) { taskGroup in
-          for generator in generators {
-            taskGroup.addTask { await generator.rawValue() }
-          }
-          result = await taskGroup.reduce(into: result) { $0.insert($1) }
+      let generators = Generator.allTestContentRecords().lazy.compactMap { $0.load() }
+      await withTaskGroup(of: Self.self) { taskGroup in
+        for generator in generators {
+          taskGroup.addTask { await generator.rawValue() }
         }
+        result = await taskGroup.reduce(into: result) { $0.insert($1) }
       }
-#endif
 
       return result
     }

Sources/Testing/Test+Discovery.swift

@@ -12,8 +12,8 @@ public import SwiftSyntax
 import SwiftSyntaxBuilder
 public import SwiftSyntaxMacros
 
-#if !hasFeature(SymbolLinkageMarkers) && SWT_NO_LEGACY_TEST_DISCOVERY
-#error("Platform-specific misconfiguration: either SymbolLinkageMarkers or legacy test discovery is required to expand #expect(exitsWith:)")
+#if !hasFeature(SymbolLinkageMarkers)
+#error("Platform-specific misconfiguration: SymbolLinkageMarkers is required to expand #expect(exitsWith:)")
 #endif
 
 /// A protocol containing the common implementation for the expansions of the
@@ -467,19 +467,6 @@ extension ExitTestConditionMacro {
         accessingWith: .identifier("accessor")
       )
 
-      // Create another local type for legacy test discovery.
-      var recordDecl: DeclSyntax?
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-      let legacyEnumName = context.makeUniqueName("__🟡$")
-      recordDecl = """
-      enum \(legacyEnumName): Testing.__TestContentRecordContainer {
-        nonisolated static var __testContentRecord: Testing.__TestContentRecord {
-          \(enumName).testContentRecord
-        }
-      }
-      """
-#endif
-
       decls.append(
         """
         @available(*, deprecated, message: "This type is an implementation detail of the testing library. Do not use it directly.")
@@ -495,8 +482,6 @@ extension ExitTestConditionMacro {
           }
 
           \(testContentRecordDecl)
-
-          \(recordDecl)
         }
         """
       )

Sources/TestingMacros/ConditionMacro.swift

@@ -13,8 +13,8 @@ public import SwiftSyntax
 import SwiftSyntaxBuilder
 public import SwiftSyntaxMacros
 
-#if !hasFeature(SymbolLinkageMarkers) && SWT_NO_LEGACY_TEST_DISCOVERY
-#error("Platform-specific misconfiguration: either SymbolLinkageMarkers or legacy test discovery is required to expand @Suite")
+#if !hasFeature(SymbolLinkageMarkers)
+#error("Platform-specific misconfiguration: SymbolLinkageMarkers is required to expand @Suite")
 #endif
 
 /// A type describing the expansion of the `@Suite` attribute macro.
@@ -166,21 +166,6 @@ public struct SuiteDeclarationMacro: MemberMacro, PeerMacro, Sendable {
       )
     )
 
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-    // Emit a type that contains a reference to the test content record.
-    let enumName = context.makeUniqueName("__🟡$")
-    result.append(
-      """
-      @available(*, deprecated, message: "This type is an implementation detail of the testing library. Do not use it directly.")
-      enum \(enumName): Testing.__TestContentRecordContainer {
-        nonisolated static var __testContentRecord: Testing.__TestContentRecord {
-          \(testContentRecordName)
-        }
-      }
-      """
-    )
-#endif
-
     return result
   }
 }

Sources/TestingMacros/SuiteDeclarationMacro.swift

@@ -13,8 +13,8 @@ public import SwiftSyntax
 import SwiftSyntaxBuilder
 public import SwiftSyntaxMacros
 
-#if !hasFeature(SymbolLinkageMarkers) && SWT_NO_LEGACY_TEST_DISCOVERY
-#error("Platform-specific misconfiguration: either SymbolLinkageMarkers or legacy test discovery is required to expand @Test")
+#if !hasFeature(SymbolLinkageMarkers)
+#error("Platform-specific misconfiguration: SymbolLinkageMarkers is required to expand @Test")
 #endif
 
 /// A type describing the expansion of the `@Test` attribute macro.
@@ -491,21 +491,6 @@ public struct TestDeclarationMacro: PeerMacro, Sendable {
       )
     )
 
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-    // Emit a type that contains a reference to the test content record.
-    let enumName = context.makeUniqueName(thunking: functionDecl, withPrefix: "__🟡$")
-    result.append(
-      """
-      @available(*, deprecated, message: "This type is an implementation detail of the testing library. Do not use it directly.")
-      enum \(enumName): Testing.__TestContentRecordContainer {
-        nonisolated static var __testContentRecord: Testing.__TestContentRecord {
-          \(testContentRecordName)
-        }
-      }
-      """
-    )
-#endif
-
     return result
   }
 }

Sources/TestingMacros/TestDeclarationMacro.swift

@@ -39,17 +39,4 @@ public protocol DiscoverableAsTestContent: Sendable, ~Copyable {
   /// By default, this type equals `Never`, indicating that this type of test
   /// content does not support hinting during discovery.
   associatedtype TestContentAccessorHint = Never
-
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-  /// A string present in the names of types containing test content records
-  /// associated with this type.
-  @available(swift, deprecated: 100000.0, message: "Do not adopt this functionality in new code. It will be removed in a future release.")
-  static var _testContentTypeNameHint: String { get }
-#endif
-}
-
-extension DiscoverableAsTestContent where Self: ~Copyable {
-  public static var _testContentTypeNameHint: String {
-    "__🟡$"
-  }
 }

Sources/_TestDiscovery/DiscoverableAsTestContent.swift

@@ -26,11 +26,6 @@ struct SectionBounds: Sendable {
   enum Kind: Equatable, Hashable, CaseIterable {
     /// The test content metadata section.
     case testContent
-
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-    /// The type metadata section.
-    case typeMetadata
-#endif
   }
 
   /// All section bounds of the given kind found in the current process.
@@ -61,10 +56,6 @@ extension SectionBounds.Kind {
     switch self {
     case .testContent:
       ("__DATA_CONST", "__swift5_tests")
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-    case .typeMetadata:
-      ("__TEXT", "__swift5_types")
-#endif
     }
   }
 }
@@ -189,10 +180,6 @@ private func _sectionBounds(_ kind: SectionBounds.Kind) -> [SectionBounds] {
       let range = switch context.pointee.kind {
       case .testContent:
         sections.swift5_tests
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-      case .typeMetadata:
-        sections.swift5_type_metadata
-#endif
       }
       let start = UnsafeRawPointer(bitPattern: range.start)
       let size = Int(clamping: range.length)
@@ -284,10 +271,6 @@ private func _sectionBounds(_ kind: SectionBounds.Kind) -> some Sequence<Section
   let sectionName = switch kind {
   case .testContent:
     ".sw5test"
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-  case .typeMetadata:
-    ".sw5tymd"
-#endif
   }
   return HMODULE.all.lazy.compactMap { _findSection(named: sectionName, in: $0) }
 }
@@ -335,25 +318,13 @@ private struct _SectionBound: Sendable, ~Copyable {
 #if SWT_TARGET_OS_APPLE
 @_silgen_name(raw: "section$start$__DATA_CONST$__swift5_tests") private nonisolated(unsafe) var _testContentSectionBegin: _SectionBound
 @_silgen_name(raw: "section$end$__DATA_CONST$__swift5_tests") private nonisolated(unsafe) var _testContentSectionEnd: _SectionBound
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-@_silgen_name(raw: "section$start$__TEXT$__swift5_types") private nonisolated(unsafe) var _typeMetadataSectionBegin: _SectionBound
-@_silgen_name(raw: "section$end$__TEXT$__swift5_types") private nonisolated(unsafe) var _typeMetadataSectionEnd: _SectionBound
-#endif
 #elseif os(Linux) || os(FreeBSD) || os(OpenBSD) || os(Android) || os(WASI)
 @_silgen_name(raw: "__start_swift5_tests") private nonisolated(unsafe) var _testContentSectionBegin: _SectionBound
 @_silgen_name(raw: "__stop_swift5_tests") private nonisolated(unsafe) var _testContentSectionEnd: _SectionBound
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-@_silgen_name(raw: "__start_swift5_type_metadata") private nonisolated(unsafe) var _typeMetadataSectionBegin: _SectionBound
-@_silgen_name(raw: "__stop_swift5_type_metadata") private nonisolated(unsafe) var _typeMetadataSectionEnd: _SectionBound
-#endif
 #else
 #warning("Platform-specific implementation missing: Runtime test discovery unavailable (static)")
 private nonisolated(unsafe) let _testContentSectionBegin = UnsafeMutableRawPointer.allocate(byteCount: 1, alignment: 16)
 private nonisolated(unsafe) let _testContentSectionEnd = _testContentSectionBegin
-#if !SWT_NO_LEGACY_TEST_DISCOVERY
-private nonisolated(unsafe) let _typeMetadataSectionBegin = UnsafeMutableRawPointer.allocate(byteCount: 1, alignment: 16)
-private nonisolated(unsafe) let _typeMetadataSectionEnd = _typeMetadataSectionBegin
-#endif
 #endif
 
 /// The common implementation of ``SectionBounds/all(_:)`` for platforms that do