SwiftIfConfig: A library to evaluate #if conditionals within a Swift syntax tree.

Package.swift

@@ -50,6 +50,7 @@ let package = Package(
     .library(name: "SwiftCompilerPluginMessageHandling", targets: ["SwiftCompilerPluginMessageHandling"]),
     .library(name: "SwiftDiagnostics", targets: ["SwiftDiagnostics"]),
     .library(name: "SwiftIDEUtils", targets: ["SwiftIDEUtils"]),
+    .library(name: "SwiftIfConfig", targets: ["SwiftIfConfig"]),
     .library(name: "SwiftOperators", targets: ["SwiftOperators"]),
     .library(name: "SwiftParser", targets: ["SwiftParser"]),
     .library(name: "SwiftParserDiagnostics", targets: ["SwiftParserDiagnostics"]),
@@ -144,6 +145,19 @@ let package = Package(
       dependencies: ["_SwiftSyntaxTestSupport", "SwiftIDEUtils", "SwiftParser", "SwiftSyntax"]
     ),
 
+    // MARK: SwiftIfConfig
+
+    .target(
+      name: "SwiftIfConfig",
+      dependencies: ["SwiftSyntax", "SwiftOperators"],
+      exclude: ["CMakeLists.txt"]
+    ),
+
+    .testTarget(
+      name: "SwiftIfConfigTest",
+      dependencies: ["_SwiftSyntaxTestSupport", "SwiftIfConfig", "SwiftParser"]
+    ),
+
     // MARK: SwiftSyntax
 
     .target(

Sources/CMakeLists.txt

@@ -37,6 +37,7 @@ add_subdirectory(SwiftDiagnostics)
 add_subdirectory(SwiftParser)
 add_subdirectory(SwiftParserDiagnostics)
 add_subdirectory(SwiftOperators)
+add_subdirectory(SwiftIfConfig)
 add_subdirectory(SwiftSyntaxBuilder)
 add_subdirectory(SwiftSyntaxMacros)
 add_subdirectory(SwiftSyntaxMacroExpansion)

Sources/SwiftIfConfig/BuildConfiguration.swift

@@ -0,0 +1,92 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+import SwiftSyntax
+
+public enum Endianness: String {
+  case little
+  case big
+}
+
+/// Describes the requested version of a module
+public enum CanImportVersion {
+  /// Any version of the module will suffice.
+  case unversioned
+
+  /// Only modules with the given version or higher will match.
+  case version(VersionTuple)
+
+  /// Only modules where the underlying Clang module has the given version or
+  /// higher will match.
+  case underlyingVersion(VersionTuple)
+}
+
+/// Captures information about the build configuration that can be
+/// queried in a `#if` expression, including OS, compiler version,
+/// enabled language features, and available modules.
+///
+/// Providing complete build configuration information effectively requires
+/// a Swift compiler, because (for example) determining whether a module can
+/// be imported is a complicated task only implemented in the Swift compiler.
+/// Therefore, many of the queries return `Bool?`, where `nil` indicates
+/// that the answer is not known. Clients that don't have a lot of context
+/// (such as an IDE that does not have access to the compiler command line)
+/// can return `nil`.
+public protocol BuildConfiguration {
+  /// Determine whether a given custom build condition has been set.
+  ///
+  /// Custom build conditions can be set by the `-D` command line option to
+  /// the Swift compiler. For example, `-DDEBUG` sets the custom condition
+  /// named `DEBUG`.
+  func isCustomConditionSet(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given feature is enabled.
+  ///
+  /// Features are determined by the Swift compiler, language mode, and other
+  /// options such as `--enable-upcoming-feature`.
+  func hasFeature(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given attribute is available.
+  ///
+  /// Attributes are determined by the Swift compiler.
+  func hasAttribute(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether a module with the given import path can be imported,
+  /// with additional version information.
+  func canImport(importPath: [String], version: CanImportVersion, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given name is the active target OS (e.g., Linux, iOS).
+  func isActiveTargetOS(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given name is the active target architecture (e.g., x86_64, arm64)
+  func isActiveTargetArchitecture(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given name is the active target environment (e.g., simulator)
+  func isActiveTargetEnvironment(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given name is the active target runtime (e.g., _ObjC vs. _Native)
+  func isActiveTargetRuntime(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// Determine whether the given name is the active target pointer authentication scheme (e.g., arm64e).
+  func isActiveTargetPointerAuthentication(name: String, syntax: ExprSyntax) -> Bool?
+
+  /// The bit width of a data pointer for the target architecture.
+  var targetPointerBitWidth: Int? { get }
+
+  /// The endianness of the target architecture.
+  var endianness: Endianness? { get }
+
+  /// The effective language version, which can be set by the user (e.g., 5.0).
+  var languageVersion: VersionTuple? { get }
+
+  /// The version of the compiler (e.g., 5.9).
+  var compilerVersion: VersionTuple? { get }
+}

Sources/SwiftIfConfig/CMakeLists.txt

@@ -0,0 +1,24 @@
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2023 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
+
+add_swift_host_library(SwiftIfConfig
+  BuildConfiguration.swift
+  IfConfigEvaluation.swift
+  IfConfigFunctions.swift
+  IfConfigRewriter.swift
+  IfConfigState.swift
+  IfConfigVisitor.swift
+  SyntaxLiteralUtils.swift
+  VersionTuple.swift
+)
+
+target_link_libraries(SwiftIfConfig PUBLIC
+  SwiftSyntax
+  SwiftDiagnostics
+  SwiftOperators
+  SwiftParser)