[Dependency Scanning] Remove obsolete placeholder module concept

This was used a long time ago for a design of a scanner which could rely on the client to specify that some modules *will be* present at a given location but are not yet during the scan. We have long ago determined that the scanner must have all modules available to it at the time of scan for soundness. This code has been stale for a couple of years and it is time to simplify things a bit by deleting it.

Author: artemcm

Sources/CSwiftScan/include/swiftscan_header.h

@@ -35,7 +35,6 @@ typedef struct {
 typedef enum {
   SWIFTSCAN_DEPENDENCY_INFO_SWIFT_TEXTUAL = 0,
   SWIFTSCAN_DEPENDENCY_INFO_SWIFT_BINARY = 1,
-  SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER = 2,
   SWIFTSCAN_DEPENDENCY_INFO_CLANG = 3
 } swiftscan_dependency_info_kind_t;
 
@@ -172,14 +171,6 @@ typedef struct {
   swiftscan_string_set_t *
   (*swiftscan_swift_binary_detail_get_header_dependencies)(swiftscan_module_details_t);
 
-  //=== Swift Placeholder Module Details query APIs -------------------------===//
-  swiftscan_string_ref_t
-  (*swiftscan_swift_placeholder_detail_get_compiled_module_path)(swiftscan_module_details_t);
-  swiftscan_string_ref_t
-  (*swiftscan_swift_placeholder_detail_get_module_doc_path)(swiftscan_module_details_t);
-  swiftscan_string_ref_t
-  (*swiftscan_swift_placeholder_detail_get_module_source_info_path)(swiftscan_module_details_t);
-
   //=== Clang Module Details query APIs -------------------------------------===//
   swiftscan_string_ref_t
   (*swiftscan_clang_detail_get_module_map_path)(swiftscan_module_details_t);

Sources/SwiftDriver/Driver/Driver.swift

@@ -638,10 +638,6 @@ public struct Driver {
   /// is shared across many targets; otherwise, a new instance is created by the driver itself.
   @_spi(Testing) public let interModuleDependencyOracle: InterModuleDependencyOracle
 
-  /// A dictionary of external targets that are a part of the same build, mapping to filesystem paths
-  /// of their module files
-  @_spi(Testing) public var externalTargetModuleDetailsMap: ExternalTargetModuleDetailsMap? = nil
-
   /// A collection of all the flags the selected toolchain's `swift-frontend` supports
   public let supportedFrontendFlags: Set<String>
 
@@ -768,6 +764,7 @@ public struct Driver {
   }
 
   @available(*, deprecated, renamed: "init(args:env:diagnosticsOutput:fileSystem:executor:integratedDriver:compilerExecutableDir:externalTargetModuleDetailsMap:interModuleDependencyOracle:)")
+  @_disfavoredOverload
   public init(
     args: [String],
     env: [String: String] = ProcessEnv.vars,
@@ -788,12 +785,12 @@ public struct Driver {
       integratedDriver: integratedDriver,
       compilerIntegratedTooling: false,
       compilerExecutableDir: compilerExecutableDir,
-      externalTargetModuleDetailsMap: externalTargetModuleDetailsMap,
       interModuleDependencyOracle: interModuleDependencyOracle
     )
   }
 
   @available(*, deprecated, renamed: "init(args:env:diagnosticsOutput:fileSystem:executor:integratedDriver:compilerIntegratedTooling:compilerExecutableDir:externalTargetModuleDetailsMap:interModuleDependencyOracle:)")
+  @_disfavoredOverload
   public init(
     args: [String],
     env: [String: String] = ProcessEnv.vars,
@@ -814,7 +811,33 @@ public struct Driver {
       integratedDriver: integratedDriver,
       compilerIntegratedTooling: false,
       compilerExecutableDir: compilerExecutableDir,
-      externalTargetModuleDetailsMap: externalTargetModuleDetailsMap,
+      interModuleDependencyOracle: interModuleDependencyOracle
+    )
+  }
+
+  @available(*, deprecated, renamed: "init(args:env:diagnosticsOutput:fileSystem:executor:integratedDriver:compilerExecutableDir:interModuleDependencyOracle:)")
+  @_disfavoredOverload
+  public init(
+    args: [String],
+    env: [String: String] = ProcessEnv.vars,
+    diagnosticsOutput: DiagnosticsOutput = .engine(DiagnosticsEngine(handlers: [Driver.stderrDiagnosticsHandler])),
+    fileSystem: FileSystem = localFileSystem,
+    executor: DriverExecutor,
+    integratedDriver: Bool = true,
+    compilerIntegratedTooling: Bool = false,
+    compilerExecutableDir: AbsolutePath? = nil,
+    externalTargetModuleDetailsMap: ExternalTargetModuleDetailsMap? = nil,
+    interModuleDependencyOracle: InterModuleDependencyOracle? = nil
+  ) throws {
+    try self.init(
+      args: args,
+      env: env,
+      diagnosticsOutput: diagnosticsOutput,
+      fileSystem: fileSystem,
+      executor: executor,
+      integratedDriver: integratedDriver,
+      compilerIntegratedTooling: false,
+      compilerExecutableDir: compilerExecutableDir,
       interModuleDependencyOracle: interModuleDependencyOracle
     )
   }
@@ -837,9 +860,6 @@ public struct Driver {
   ///   Swift compiler image which contains symbols normally queried from a libSwiftScan instance.
   /// - Parameter compilerExecutableDir: Directory that contains the compiler executable to be used.
   ///   Used when in `integratedDriver` mode as a substitute for the driver knowing its executable path.
-  /// - Parameter externalTargetModuleDetailsMap: A dictionary of external targets that are a part of
-  ///   the same build, mapping to a details value which includes a filesystem path of their
-  ///   `.swiftmodule` and a flag indicating whether the external target is a framework.
   /// - Parameter interModuleDependencyOracle: An oracle for querying inter-module dependencies,
   ///   shared across different module builds by a build system.
   public init(
@@ -851,7 +871,6 @@ public struct Driver {
     integratedDriver: Bool = true,
     compilerIntegratedTooling: Bool = false,
     compilerExecutableDir: AbsolutePath? = nil,
-    externalTargetModuleDetailsMap: ExternalTargetModuleDetailsMap? = nil,
     interModuleDependencyOracle: InterModuleDependencyOracle? = nil
   ) throws {
     self.env = env
@@ -869,7 +888,6 @@ public struct Driver {
     self.diagnosticEngine = diagnosticsEngine
 
     self.executor = executor
-    self.externalTargetModuleDetailsMap = externalTargetModuleDetailsMap
 
     if case .subcommand = try Self.invocationRunMode(forArgs: args).mode {
       throw Error.subcommandPassedToDriver
@@ -1775,8 +1793,6 @@ extension Driver {
           pathString = pathString + "[" + moduleName + "]"
         case .clang(let moduleName):
           pathString = pathString + "[" + moduleName + "](ObjC)"
-        case .swiftPlaceholder(_):
-          fatalError("Unexpected unresolved Placeholder module")
         }
         if index < path.count - 1 {
           pathString = pathString + " -> "

Sources/SwiftDriver/ExplicitModuleBuilds/ExplicitDependencyBuildPlanner.swift

@@ -33,6 +33,7 @@ public struct ChainedBridgingHeaderFile {
   let content: String
 }
 
+// Deprecated
 public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalTargetModuleDetails]
 
 /// In Explicit Module Build mode, this planner is responsible for generating and providing
@@ -363,8 +364,6 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
                                   headerDependencies: prebuiltModuleDetails.headerDependencyPaths,
                                   isFramework: isFramework,
                                   moduleCacheKey: prebuiltModuleDetails.moduleCacheKey))
-      case .swiftPlaceholder:
-        fatalError("Unresolved placeholder dependencies at planning stage: \(dependencyId) of \(moduleId)")
     }
   }
 

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift

@@ -13,49 +13,6 @@
 import func TSCBasic.topologicalSort
 import protocol TSCBasic.FileSystem
 
-@_spi(Testing) public extension InterModuleDependencyGraph {
-  /// For targets that are built alongside the driver's current module, the scanning action will report them as
-  /// textual targets to be built from source. Because we can rely on these targets to have been built prior
-  /// to the driver's current target, we resolve such external targets as prebuilt binary modules, in the graph.
-  mutating func resolveExternalDependencies(for externalTargetModuleDetailsMap: ExternalTargetModuleDetailsMap)
-  throws {
-    for (externalModuleId, externalModuleDetails) in externalTargetModuleDetailsMap {
-      let externalModulePath = externalModuleDetails.path
-      // Replace the occurrence of a Swift module to-be-built from source-file
-      // to an info that describes a pre-built binary module.
-      let swiftModuleId: ModuleDependencyId = .swift(externalModuleId.moduleName)
-      let prebuiltModuleId: ModuleDependencyId = .swiftPrebuiltExternal(externalModuleId.moduleName)
-      if let currentInfo = modules[swiftModuleId],
-         externalModuleId.moduleName != mainModuleName {
-        let newExternalModuleDetails =
-        SwiftPrebuiltExternalModuleDetails(compiledModulePath:
-                                            TextualVirtualPath(path: VirtualPath.absolute(externalModulePath).intern()),
-                                           isFramework: externalModuleDetails.isFramework)
-        let newInfo = ModuleInfo(modulePath: TextualVirtualPath(path: VirtualPath.absolute(externalModulePath).intern()),
-                                 sourceFiles: [],
-                                 directDependencies: currentInfo.directDependencies,
-                                 linkLibraries: currentInfo.linkLibraries,
-                                 details: .swiftPrebuiltExternal(newExternalModuleDetails))
-        Self.replaceModule(originalId: swiftModuleId, replacementId: prebuiltModuleId,
-                           replacementInfo: newInfo, in: &modules)
-      } else if let currentPrebuiltInfo = modules[prebuiltModuleId] {
-        // Just update the isFramework bit on this prebuilt module dependency
-        let newExternalModuleDetails =
-        SwiftPrebuiltExternalModuleDetails(compiledModulePath:
-                                            TextualVirtualPath(path: VirtualPath.absolute(externalModulePath).intern()),
-                                           isFramework: externalModuleDetails.isFramework)
-        let newInfo = ModuleInfo(modulePath: TextualVirtualPath(path: VirtualPath.absolute(externalModulePath).intern()),
-                                 sourceFiles: [],
-                                 directDependencies: currentPrebuiltInfo.directDependencies,
-                                 linkLibraries: currentPrebuiltInfo.linkLibraries,
-                                 details: .swiftPrebuiltExternal(newExternalModuleDetails))
-        Self.replaceModule(originalId: prebuiltModuleId, replacementId: prebuiltModuleId,
-                           replacementInfo: newInfo, in: &modules)
-      }
-    }
-  }
-}
-
 extension InterModuleDependencyGraph {
   var topologicalSorting: [ModuleDependencyId] {
     get throws {
@@ -114,10 +71,6 @@ extension InterModuleDependencyGraph {
                                  in moduleInfoMap: inout ModuleInfoMap) {
     for moduleId in moduleInfoMap.keys {
       var moduleInfo = moduleInfoMap[moduleId]!
-      // Skip over placeholders, they do not have dependencies
-      if case .swiftPlaceholder(_) = moduleId {
-        continue
-      }
       if let originalModuleIndex = moduleInfo.directDependencies?.firstIndex(of: originalId) {
         moduleInfo.directDependencies![originalModuleIndex] = replacementId;
         moduleInfoMap[moduleId] = moduleInfo
@@ -246,9 +199,6 @@ internal extension InterModuleDependencyGraph {
       return try casOutputMissing(clangDetails.moduleCacheKey)
     case .swiftPrebuiltExternal(_):
       return false;
-    case .swiftPlaceholder(_):
-      // TODO: This should never ever happen. Hard error?
-      return true;
     }
   }
 
@@ -340,9 +290,6 @@ internal extension InterModuleDependencyGraph {
       }
     case .swiftPrebuiltExternal(_):
       return true;
-    case .swiftPlaceholder(_):
-      // TODO: This should never ever happen. Hard error?
-      return false;
     }
 
     return true

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/InterModuleDependencyGraph.swift

@@ -18,14 +18,12 @@ public typealias ModuleInfoMap = [ModuleDependencyId: ModuleInfo]
 
 public enum ModuleDependencyId: Hashable {
   case swift(String)
-  case swiftPlaceholder(String)
   case swiftPrebuiltExternal(String)
   case clang(String)
 
   public var moduleName: String {
     switch self {
     case .swift(let name): return name
-    case .swiftPlaceholder(let name): return name
     case .swiftPrebuiltExternal(let name): return name
     case .clang(let name): return name
     }
@@ -34,7 +32,6 @@ public enum ModuleDependencyId: Hashable {
   internal var moduleNameForDiagnostic: String {
     switch self {
     case .swift(let name): return name
-    case .swiftPlaceholder(let name): return name + "(placeholder)"
     case .swiftPrebuiltExternal(let name): return name + "(swiftmodule)"
     case .clang(let name): return name + "(pcm)"
     }
@@ -44,7 +41,6 @@ public enum ModuleDependencyId: Hashable {
 extension ModuleDependencyId: Codable {
   enum CodingKeys: CodingKey {
     case swift
-    case swiftPlaceholder
     case swiftPrebuiltExternal
     case clang
   }
@@ -56,16 +52,11 @@ extension ModuleDependencyId: Codable {
       self = .swift(moduleName)
     } catch {
       do {
-        let moduleName =  try container.decode(String.self, forKey: .swiftPlaceholder)
-        self = .swiftPlaceholder(moduleName)
+        let moduleName =  try container.decode(String.self, forKey: .swiftPrebuiltExternal)
+        self = .swiftPrebuiltExternal(moduleName)
       } catch {
-        do {
-          let moduleName =  try container.decode(String.self, forKey: .swiftPrebuiltExternal)
-          self = .swiftPrebuiltExternal(moduleName)
-        } catch {
-          let moduleName =  try container.decode(String.self, forKey: .clang)
-          self = .clang(moduleName)
-        }
+        let moduleName =  try container.decode(String.self, forKey: .clang)
+        self = .clang(moduleName)
       }
     }
   }
@@ -75,8 +66,6 @@ extension ModuleDependencyId: Codable {
     switch self {
       case .swift(let moduleName):
         try container.encode(moduleName, forKey: .swift)
-      case .swiftPlaceholder(let moduleName):
-        try container.encode(moduleName, forKey: .swiftPlaceholder)
       case .swiftPrebuiltExternal(let moduleName):
         try container.encode(moduleName, forKey: .swiftPrebuiltExternal)
       case .clang(let moduleName):
@@ -150,15 +139,6 @@ public struct SwiftModuleDetails: Codable, Hashable {
   public var chainedBridgingHeaderContent: String?
 }
 
-/// Details specific to Swift placeholder dependencies.
-public struct SwiftPlaceholderModuleDetails: Codable, Hashable {
-  /// The path to the .swiftModuleDoc file.
-  var moduleDocPath: TextualVirtualPath?
-
-  /// The path to the .swiftSourceInfo file.
-  var moduleSourceInfoPath: TextualVirtualPath?
-}
-
 /// Details specific to Swift externally-pre-built modules.
 public struct SwiftPrebuiltExternalModuleDetails: Codable, Hashable {
   /// The path to the already-compiled module that must be used instead of
@@ -224,10 +204,6 @@ public struct ModuleInfo: Codable, Hashable {
     /// a bridging header.
     case swift(SwiftModuleDetails)
 
-    /// Swift placeholder modules carry additional details that specify their
-    /// module doc path and source info paths.
-    case swiftPlaceholder(SwiftPlaceholderModuleDetails)
-
     /// Swift externally-prebuilt modules must communicate the path to pre-built binary artifacts
     case swiftPrebuiltExternal(SwiftPrebuiltExternalModuleDetails)
 
@@ -251,7 +227,6 @@ public struct ModuleInfo: Codable, Hashable {
 extension ModuleInfo.Details: Codable {
   enum CodingKeys: CodingKey {
     case swift
-    case swiftPlaceholder
     case swiftPrebuiltExternal
     case clang
   }
@@ -263,18 +238,12 @@ extension ModuleInfo.Details: Codable {
       self = .swift(details)
     } catch {
       do {
-        let details = try container.decode(SwiftPlaceholderModuleDetails.self,
-                                           forKey: .swiftPlaceholder)
-        self = .swiftPlaceholder(details)
+        let details = try container.decode(SwiftPrebuiltExternalModuleDetails.self,
+                                           forKey: .swiftPrebuiltExternal)
+        self = .swiftPrebuiltExternal(details)
       } catch {
-        do {
-          let details = try container.decode(SwiftPrebuiltExternalModuleDetails.self,
-                                             forKey: .swiftPrebuiltExternal)
-          self = .swiftPrebuiltExternal(details)
-        } catch {
-          let details = try container.decode(ClangModuleDetails.self, forKey: .clang)
-          self = .clang(details)
-        }
+        let details = try container.decode(ClangModuleDetails.self, forKey: .clang)
+        self = .clang(details)
       }
     }
   }
@@ -284,8 +253,6 @@ extension ModuleInfo.Details: Codable {
     switch self {
       case .swift(let details):
         try container.encode(details, forKey: .swift)
-      case .swiftPlaceholder(let details):
-        try container.encode(details, forKey: .swiftPlaceholder)
       case .swiftPrebuiltExternal(let details):
         try container.encode(details, forKey: .swiftPrebuiltExternal)
       case .clang(let details):

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/InterModuleDependencyOracle.swift

@@ -32,17 +32,7 @@ import Dispatch
 /// An abstraction of a cache and query-engine of inter-module dependencies
 public class InterModuleDependencyOracle {
   /// Allow external clients to instantiate the oracle
-  /// - Parameter scannerRequiresPlaceholderModules: Configures this driver's/oracle's scanner invocations to
-  /// specify external module dependencies to be treated as placeholders. This is required in contexts
-  /// where the dependency scanning action is invoked for a module which depends on another module
-  /// that is part of the same build but has not yet been built. Treating it as a placeholder
-  /// will allow the scanning action to not fail when it fails to detect this dependency on
-  /// the filesystem. For example, SwiftPM plans all targets belonging to a package before *any* of them
-  /// are built. So this setting is meant to be used there. In contexts where planning a module
-  /// necessarily means all of its dependencies have already been built this is not necessary.
-  public init(scannerRequiresPlaceholderModules: Bool = false) {
-    self.scannerRequiresPlaceholderModules = scannerRequiresPlaceholderModules
-  }
+  public init() {}
 
   @_spi(Testing) public func getDependencies(workingDirectory: AbsolutePath,
                                              moduleAliases: [String: String]? = nil,
@@ -200,8 +190,6 @@ public class InterModuleDependencyOracle {
   /// A reference to an instance of the compiler's libSwiftScan shared library
   private var swiftScanLibInstance: SwiftScan? = nil
 
-  internal let scannerRequiresPlaceholderModules: Bool
-
   internal struct CASConfig: Hashable, Equatable {
     static func == (lhs: InterModuleDependencyOracle.CASConfig, rhs: InterModuleDependencyOracle.CASConfig) -> Bool {
       return lhs.onDiskPath == rhs.onDiskPath &&