Unify PackageDescription 4.0 and 4.2+ into a single library by using …

…availability annotations instead of #if

Replace the compile-time conditionals in PackageDescription with availability annotations.  This lets us build a single PackageDescription, which will make the build scripts easier (with the goal of being able to build it entirely from the package itself).

As part of this we also clean up the runtime library subdirectories.  Until now we've had PackagePlugin directly in the runtime library directory, and PackageDescription under subdirectories called "4" and "4_2".  This has sufficed in keeping PackageDescription and PackagePlugin in separate directories (so that a manifest or plugin script can't import both).

This needs to be changed now that there is only one version of a PackageDescription, and anyway it's time to clean this up.  So as part of this we also establish two subdirectories for the runtime APIs: "ManifestAPI" and "PluginAPI".  If we add more kinds of scripts, we can then add new subdirectories here.

rdar://77441062

Package.swift

@@ -113,19 +113,25 @@ let package = Package(
         ),
     ],
     targets: [
-        // The `PackageDescription` targets define the API which is available to
-        // the `Package.swift` manifest files. We build the latest API version
-        // here which is used when building and running swiftpm without the
-        // bootstrap script.
+        // The `PackageDescription` target provides the API that is available
+        // to `Package.swift` manifests. Here we build a debug version of the
+        // library; the bootstrap scripts build the deployable version.
         .target(
-            /** Package Definition API */
             name: "PackageDescription",
             swiftSettings: [
-                .define("PACKAGE_DESCRIPTION_4_2"),
+                .unsafeFlags(["-package-description-version", "999.0"]),
+                .unsafeFlags(["-enable-library-evolution"])
             ]),
-
+
+        // The `PackagePlugin` target provides the API that is available to
+        // plugin scripts. Here we build a debug version of the library; the
+        // bootstrap scripts build the deployable version.
         .target(
-            name: "PackagePlugin"),
+            name: "PackagePlugin",
+            swiftSettings: [
+                .unsafeFlags(["-package-description-version", "999.0"]),
+                .unsafeFlags(["-enable-library-evolution"])
+            ]),
 
         // MARK: SwiftPM specific support libraries
 

Sources/PackageDescription/CMakeLists.txt

@@ -1,75 +1,73 @@
 # This source file is part of the Swift.org open source project
 #
-# Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+# Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 # Licensed under Apache License v2.0 with Runtime Library Exception
 #
 # See http://swift.org/LICENSE.txt for license information
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
-foreach(PACKAGE_DESCRIPTION_VERSION 4 4_2)
-    add_library(PD${PACKAGE_DESCRIPTION_VERSION}
-        BuildSettings.swift
-        LanguageStandardSettings.swift
-        PackageDescription.swift
-        PackageDependency.swift
-        PackageRequirement.swift
-        Product.swift
-        Resource.swift
-        SupportedPlatforms.swift
-        Target.swift
-        Version.swift
-        Version+StringLiteralConvertible.swift)
+add_library(PackageDescription
+  BuildSettings.swift
+  LanguageStandardSettings.swift
+  PackageDescription.swift
+  PackageDependency.swift
+  PackageRequirement.swift
+  Product.swift
+  Resource.swift
+  SupportedPlatforms.swift
+  Target.swift
+  Version.swift
+  Version+StringLiteralConvertible.swift)
 
-    target_compile_definitions(PD${PACKAGE_DESCRIPTION_VERSION} PRIVATE
-        PACKAGE_DESCRIPTION_${PACKAGE_DESCRIPTION_VERSION})
+target_compile_options(PackageDescription PUBLIC
+  $<$<COMPILE_LANGUAGE:Swift>:-package-description-version$<SEMICOLON>999.0>)
+target_compile_options(PackageDescription PUBLIC
+  $<$<COMPILE_LANGUAGE:Swift>:-enable-library-evolution>)
 
-    if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
-        set(SWIFT_INTERFACE_PATH ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}/PackageDescription.swiftinterface)
-        target_compile_options(PD${PACKAGE_DESCRIPTION_VERSION} PUBLIC
-            $<$<COMPILE_LANGUAGE:Swift>:-enable-library-evolution>)
-        target_compile_options(PD${PACKAGE_DESCRIPTION_VERSION} PUBLIC
-            $<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${SWIFT_INTERFACE_PATH}>)
-        target_link_options(PD${PACKAGE_DESCRIPTION_VERSION} PRIVATE
-            "SHELL:-Xlinker -install_name -Xlinker @rpath/libPackageDescription.dylib")
-    endif()
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
+  set(SWIFT_INTERFACE_PATH ${CMAKE_BINARY_DIR}/pm/ManifestAPI/PackageDescription.swiftinterface)
+  target_compile_options(PackageDescription PUBLIC
+    $<$<COMPILE_LANGUAGE:Swift>:-emit-module-interface-path$<SEMICOLON>${SWIFT_INTERFACE_PATH}>)
+  target_link_options(PackageDescription PRIVATE
+    "SHELL:-Xlinker -install_name -Xlinker @rpath/libPackageDescription.dylib")
+endif()
 
-    set_target_properties(PD${PACKAGE_DESCRIPTION_VERSION} PROPERTIES
-        Swift_MODULE_NAME PackageDescription
-        Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}
-        INSTALL_NAME_DIR \\@rpath
-        OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}
-        OUTPUT_NAME PackageDescription
-        ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}
-        LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}
-        RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}
-    )
+set_target_properties(PackageDescription PROPERTIES
+    Swift_MODULE_NAME PackageDescription
+    Swift_MODULE_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
+    INSTALL_NAME_DIR \\@rpath
+    OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
+    OUTPUT_NAME PackageDescription
+    ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
+    LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
+    RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/pm/ManifestAPI
+)
 
-    if(NOT CMAKE_SYSTEM_NAME STREQUAL Darwin)
-      if(Foundation_FOUND)
-        target_link_libraries(PD${PACKAGE_DESCRIPTION_VERSION} PRIVATE
-          Foundation)
-      endif()
-      target_link_options(PD${PACKAGE_DESCRIPTION_VERSION} PRIVATE
-        "SHELL:-no-toolchain-stdlib-rpath")
-      set_target_properties(PD${PACKAGE_DESCRIPTION_VERSION} PROPERTIES
-          BUILD_WITH_INSTALL_RPATH TRUE
-          INSTALL_RPATH "$ORIGIN/../../$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>")
-    endif()
+if(NOT CMAKE_SYSTEM_NAME STREQUAL Darwin)
+  if(Foundation_FOUND)
+    target_link_libraries(PackageDescription PRIVATE
+      Foundation)
+  endif()
+  target_link_options(PackageDescription PRIVATE
+    "SHELL:-no-toolchain-stdlib-rpath")
+  set_target_properties(PackageDescription PROPERTIES
+    BUILD_WITH_INSTALL_RPATH TRUE
+    INSTALL_RPATH "$ORIGIN/../../$<LOWER_CASE:${CMAKE_SYSTEM_NAME}>")
+endif()
 
-    if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
-        install(FILES
-            ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}/PackageDescription.swiftinterface
-            ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}/PackageDescription.swiftdoc
-            DESTINATION lib/swift/pm/${PACKAGE_DESCRIPTION_VERSION}
-        )
-    else()
-        install(FILES
-            ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}/PackageDescription.swiftmodule
-            ${CMAKE_BINARY_DIR}/pm/${PACKAGE_DESCRIPTION_VERSION}/PackageDescription.swiftdoc
-            DESTINATION lib/swift/pm/${PACKAGE_DESCRIPTION_VERSION}
-        )
-    endif()
+if(CMAKE_HOST_SYSTEM_NAME STREQUAL Darwin)
+  install(FILES
+    ${CMAKE_BINARY_DIR}/pm/ManifestAPI/PackageDescription.swiftinterface
+    ${CMAKE_BINARY_DIR}/pm/ManifestAPI/PackageDescription.swiftdoc
+    DESTINATION lib/swift/pm/ManifestAPI
+  )
+else()
+  install(FILES
+    ${CMAKE_BINARY_DIR}/pm/ManifestAPI/PackageDescription.swiftmodule
+    ${CMAKE_BINARY_DIR}/pm/ManifestAPI/PackageDescription.swiftdoc
+    DESTINATION lib/swift/pm/ManifestAPI
+  )
+endif()
 
-    install(TARGETS PD${PACKAGE_DESCRIPTION_VERSION}
-      DESTINATION lib/swift/pm/${PACKAGE_DESCRIPTION_VERSION})
-endforeach()
+install(TARGETS PackageDescription
+  DESTINATION lib/swift/pm/ManifestAPI)

Sources/PackageDescription/LanguageStandardSettings.swift

@@ -144,7 +144,6 @@ public enum CXXLanguageStandard: String, Encodable {
     case gnucxx20 = "gnu++20"
 }
 
-#if !PACKAGE_DESCRIPTION_4
 /// The version of the Swift language to use for compiling Swift sources in the package.
 public enum SwiftVersion {
     @available(_PackageDescription, introduced: 4, obsoleted: 5)
@@ -187,4 +186,3 @@ extension SwiftVersion: Encodable {
         try container.encode(value)
     }
 }
-#endif

Sources/PackageDescription/PackageDependency.swift

@@ -147,11 +147,7 @@ extension Package.Dependency {
         url: String,
         _ range: Range<Version>
     ) -> Package.Dependency {
-      #if PACKAGE_DESCRIPTION_4
         return .init(name: nil, url: url, requirement: .rangeItem(range))
-      #else
-        return .init(name: nil, url: url, requirement: ._rangeItem(range))
-      #endif
     }
 
     /// Adds a package dependency starting with a specific minimum version, up to
@@ -172,11 +168,7 @@ extension Package.Dependency {
         url: String,
         _ range: Range<Version>
     ) -> Package.Dependency {
-      #if PACKAGE_DESCRIPTION_4
         return .init(name: name, url: url, requirement: .rangeItem(range))
-      #else
-        return .init(name: name, url: url, requirement: ._rangeItem(range))
-      #endif
     }
 
     /// Adds a package dependency starting with a specific minimum version, going
@@ -202,11 +194,7 @@ extension Package.Dependency {
             upper.major, upper.minor, upper.patch + 1,
             prereleaseIdentifiers: upper.prereleaseIdentifiers,
             buildMetadataIdentifiers: upper.buildMetadataIdentifiers)
-      #if PACKAGE_DESCRIPTION_4
         return .init(name: nil, url: url, requirement: .rangeItem(range.lowerBound..<upperBound))
-      #else
-        return .init(name: nil, url: url, requirement: ._rangeItem(range.lowerBound..<upperBound))
-      #endif
     }
 
     /// Adds a package dependency starting with a specific minimum version, going
@@ -233,14 +221,9 @@ extension Package.Dependency {
             upper.major, upper.minor, upper.patch + 1,
             prereleaseIdentifiers: upper.prereleaseIdentifiers,
             buildMetadataIdentifiers: upper.buildMetadataIdentifiers)
-      #if PACKAGE_DESCRIPTION_4
         return .init(name: name, url: url, requirement: .rangeItem(range.lowerBound..<upperBound))
-      #else
-        return .init(name: name, url: url, requirement: ._rangeItem(range.lowerBound..<upperBound))
-      #endif
     }
 
-  #if !PACKAGE_DESCRIPTION_4
     /// Adds a package dependency to a local package on the filesystem.
     ///
     /// The Swift Package Manager uses the package dependency as-is
@@ -253,7 +236,7 @@ extension Package.Dependency {
     public static func package(
         path: String
     ) -> Package.Dependency {
-        return .init(name: nil, url: path, requirement: ._localPackageItem)
+        return .init(name: nil, url: path, requirement: .localPackageItem)
     }
 
     /// Adds a package dependency to a local package on the filesystem.
@@ -271,9 +254,8 @@ extension Package.Dependency {
         name: String? = nil,
         path: String
     ) -> Package.Dependency {
-        return .init(name: name, url: path, requirement: ._localPackageItem)
+        return .init(name: name, url: path, requirement: .localPackageItem)
     }
-  #endif
 }
 
 // Mark common APIs used by mistake as unavailable to provide better error messages.