Introduce SWIFT_ENABLE_REFLECTION to turn on/off the support for Mirrors and reflection (swiftlang#33617)

Author: kubamracek

stdlib/CMakeLists.txt

@@ -102,6 +102,10 @@ set(SWIFT_STDLIB_ENABLE_LTO OFF CACHE STRING "Build Swift stdlib with LTO. One
     must specify the form of LTO by setting this to one of: 'full', 'thin'. This
     option only affects the standard library and runtime, not tools.")
 
+option(SWIFT_ENABLE_REFLECTION
+  "Build stdlib with support for runtime reflection and mirrors."
+  TRUE)
+
 #
 # End of user-configurable options.
 #

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -315,6 +315,10 @@ function(_add_target_variant_c_compile_flags)
     list(APPEND result "-DSWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES")
   endif()
 
+  if(SWIFT_ENABLE_REFLECTION)
+    list(APPEND result "-DSWIFT_ENABLE_REFLECTION")
+  endif()
+
   if(SWIFT_RUNTIME_MACHO_NO_DYLD)
     list(APPEND result "-DSWIFT_RUNTIME_MACHO_NO_DYLD")
   endif()

stdlib/cmake/modules/SwiftSource.cmake

@@ -432,6 +432,12 @@ function(_compile_swift_files
     list(APPEND swift_flags "-Xfrontend" "-emit-sorted-sil")
   endif()
 
+  if(NOT SWIFT_ENABLE_REFLECTION)
+    list(APPEND swift_flags "-Xfrontend" "-disable-reflection-metadata")
+  else()
+    list(APPEND swift_flags "-D" "SWIFT_ENABLE_REFLECTION")
+  endif()
+
   # FIXME: Cleaner way to do this?
   if(SWIFTFILE_IS_STDLIB_CORE)
     list(APPEND swift_flags

stdlib/public/core/AnyHashable.swift

@@ -252,13 +252,15 @@ extension AnyHashable: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension AnyHashable: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self,
       children: ["value": base])
   }
 }
+#endif
 
 @available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *)
 extension AnyHashable: _HasCustomAnyHashableRepresentation {

stdlib/public/core/Array.swift

@@ -1414,6 +1414,7 @@ extension Array {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Array: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1423,6 +1424,7 @@ extension Array: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension Array: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/ArraySlice.swift

@@ -1118,6 +1118,7 @@ extension ArraySlice: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ArraySlice: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1127,6 +1128,7 @@ extension ArraySlice: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ArraySlice: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/ClosedRange.swift

@@ -396,12 +396,14 @@ extension ClosedRange: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ClosedRange: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self, children: ["lowerBound": lowerBound, "upperBound": upperBound])
   }
 }
+#endif
 
 extension ClosedRange {
   /// Returns a copy of this range clamped to the given limiting range.

stdlib/public/core/CollectionOfOne.swift

@@ -165,11 +165,13 @@ extension CollectionOfOne: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension CollectionOfOne: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(self, children: ["element": _element])
   }
 }
+#endif
 
 extension CollectionOfOne: Sendable where Element: Sendable { }
 extension CollectionOfOne.Iterator: Sendable where Element: Sendable { }

stdlib/public/core/ContiguousArray.swift

@@ -1019,6 +1019,7 @@ extension ContiguousArray: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ContiguousArray: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1028,6 +1029,7 @@ extension ContiguousArray: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ContiguousArray: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/DebuggerSupport.swift

@@ -12,6 +12,8 @@
 
 import SwiftShims
 
+#if SWIFT_ENABLE_REFLECTION
+
 @frozen // namespace
 public enum _DebuggerSupport {
   private enum CollectionStatus {
@@ -262,6 +264,8 @@ public func _stringForPrintObject(_ value: Any) -> String {
   return _DebuggerSupport.stringForPrintObject(value)
 }
 
+#endif // SWIFT_ENABLE_REFLECTION
+
 public func _debuggerTestingCheckExpect(_: String, _: String) { }
 
 // Utilities to get refcount(s) of class objects.