[Dependency Scanning] Remove obsolete placeholder module concept

include/swift-c/DependencyScan/DependencyScan.h

@@ -36,7 +36,6 @@ typedef enum {
   // SwiftInterface and SwiftSource.
   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;
 
@@ -273,7 +272,8 @@ swiftscan_swift_binary_detail_get_module_cache_key(
 SWIFTSCAN_PUBLIC swiftscan_string_ref_t
 swiftscan_swift_binary_detail_get_user_module_version(
     swiftscan_module_details_t details);
-//=== Swift Placeholder Module Details query APIs -------------------------===//
+
+//=== Swift Placeholder Module Details query APIs - DEPRECATED -----------===//
 
 SWIFTSCAN_PUBLIC swiftscan_string_ref_t
 swiftscan_swift_placeholder_detail_get_compiled_module_path(

include/swift/AST/DiagnosticsFrontend.def

@@ -362,14 +362,6 @@ ERROR(explicit_swift_module_map_corrupted,none,
       "explicit Swift module map from %0 is malformed",
       (StringRef))
 
-ERROR(placeholder_dependency_module_map_missing,none,
-      "cannot open Swift placeholder dependency module map from %0",
-      (StringRef))
-
-ERROR(placeholder_dependency_module_map_corrupted,none,
-      "Swift placeholder dependency module map from %0 is malformed",
-      (StringRef))
-
 ERROR(const_extract_protocol_list_input_file_missing,none,
       "cannot open constant extraction protocol list input file from %0",
       (StringRef))

include/swift/AST/ModuleDependencies.h

@@ -69,30 +69,7 @@ enum class ModuleDependencyKind : int8_t {
   Clang,
   // Used to model the translation unit's source module
   SwiftSource,
-  // Placeholder dependencies are a kind of dependencies used only by the
-  // dependency scanner. They are swift modules that the scanner will not be
-  // able to locate in its search paths and which are the responsibility of the
-  // scanner's client to ensure are provided.
-  //
-  // Placeholder dependencies will be specified in the scanner's output
-  // dependency graph where it is the responsibility of the scanner's client to
-  // ensure required post-processing takes place to "resolve" them. In order to
-  // do so, the client (swift driver, or any other client build system) is
-  // expected to have access to a full dependency graph of all placeholder
-  // dependencies and be able to replace placeholder nodes in the dependency
-  // graph with their full dependency trees, `uniquing` common dependency module
-  // nodes in the process.
-  //
-  // One example where placeholder dependencies are employed is when using
-  // SwiftPM in Explicit Module Build mode. SwiftPM constructs a build plan for
-  // all targets ahead-of-time. When planning a build for a target that depends
-  // on other targets, the dependency scanning action is not able to locate
-  // dependency target modules, because they have not yet been built. Instead,
-  // the build system treats them as placeholder dependencies and resolves them
-  // with `actual` dependencies in a post-processing step once dependency graphs
-  // of all targets, individually, have been computed.
-  SwiftPlaceholder,
-  LastKind = SwiftPlaceholder + 1
+  LastKind = SwiftSource + 1
 };
 
 /// This is used to idenfity a specific macro plugin dependency.
@@ -537,39 +514,6 @@ class ClangModuleDependencyStorage : public ModuleDependencyInfoStorageBase {
   }
 };
 
-/// Describes an placeholder Swift module dependency module stub.
-///
-/// This class is mostly an implementation detail for \c ModuleDependencyInfo.
-
-class SwiftPlaceholderModuleDependencyStorage
-    : public ModuleDependencyInfoStorageBase {
-public:
-  SwiftPlaceholderModuleDependencyStorage(StringRef compiledModulePath,
-                                          StringRef moduleDocPath,
-                                          StringRef sourceInfoPath)
-      : ModuleDependencyInfoStorageBase(ModuleDependencyKind::SwiftPlaceholder, {}, {},
-                                        {}),
-        compiledModulePath(compiledModulePath), moduleDocPath(moduleDocPath),
-        sourceInfoPath(sourceInfoPath) {}
-
-  ModuleDependencyInfoStorageBase *clone() const override {
-    return new SwiftPlaceholderModuleDependencyStorage(*this);
-  }
-
-  /// The path to the .swiftmodule file.
-  const std::string compiledModulePath;
-
-  /// The path to the .swiftModuleDoc file.
-  const std::string moduleDocPath;
-
-  /// The path to the .swiftSourceInfo file.
-  const std::string sourceInfoPath;
-
-  static bool classof(const ModuleDependencyInfoStorageBase *base) {
-    return base->dependencyKind == ModuleDependencyKind::SwiftPlaceholder;
-  }
-};
-
 // MARK: Module Dependency Info
 /// Describes the dependencies of a given module.
 ///
@@ -670,16 +614,6 @@ class ModuleDependencyInfo {
         CASFileSystemRootID, clangIncludeTreeRoot, moduleCacheKey, IsSystem));
   }
 
-  /// Describe a placeholder dependency swift module.
-  static ModuleDependencyInfo
-  forPlaceholderSwiftModuleStub(StringRef compiledModulePath,
-                                StringRef moduleDocPath,
-                                StringRef sourceInfoPath) {
-    return ModuleDependencyInfo(
-        std::make_unique<SwiftPlaceholderModuleDependencyStorage>(
-            compiledModulePath, moduleDocPath, sourceInfoPath));
-  }
-
   /// Retrieve the module-level imports.
   ArrayRef<ScannerImportStatementInfo> getModuleImports() const {
     return storage->moduleImports;
@@ -898,7 +832,7 @@ class ModuleDependencyInfo {
   bool isTestableImport(StringRef moduleName) const;
 
   /// Whether the dependencies are for a Swift module: either Textual, Source,
-  /// Binary, or Placeholder.
+  /// or Binary
   bool isSwiftModule() const;
 
   /// Whether the dependencies are for a textual interface Swift module or a
@@ -914,9 +848,6 @@ class ModuleDependencyInfo {
   /// Whether the dependencies are for a binary Swift module.
   bool isSwiftBinaryModule() const;
 
-  /// Whether this represents a placeholder module stub
-  bool isSwiftPlaceholderModule() const;
-
   /// Whether the dependencies are for a Clang module.
   bool isClangModule() const;
 
@@ -935,10 +866,6 @@ class ModuleDependencyInfo {
   /// Retrieve the dependencies for a Clang module.
   const ClangModuleDependencyStorage *getAsClangModule() const;
 
-  /// Retrieve the dependencies for a placeholder dependency module stub.
-  const SwiftPlaceholderModuleDependencyStorage *
-  getAsPlaceholderDependencyModule() const;
-
   /// Add a dependency on the given module, if it was not already in the set.
   void
   addOptionalModuleImport(StringRef module, bool isExported,

include/swift/DependencyScan/DependencyScanImpl.h

@@ -43,7 +43,6 @@ struct swiftscan_dependency_info_s {
   /// "swiftInterface"
   /// "swiftSource"
   /// "swiftBinary"
-  /// "swiftPlaceholder"
   /// "clang""
   swiftscan_string_ref_t module_name;
 
@@ -183,19 +182,6 @@ typedef struct {
   swiftscan_string_ref_t user_module_version;
 } swiftscan_swift_binary_details_t;
 
-/// Swift placeholder modules carry additional details that specify their
-/// module doc path and source info paths.
-typedef struct {
-  /// The path to the pre-compiled binary module
-  swiftscan_string_ref_t compiled_module_path;
-
-  /// The path to the .swiftModuleDoc file.
-  swiftscan_string_ref_t module_doc_path;
-
-  /// The path to the .swiftSourceInfo file.
-  swiftscan_string_ref_t module_source_info_path;
-} swiftscan_swift_placeholder_details_t;
-
 /// Clang modules are built from a module map file.
 typedef struct {
   /// The path to the module map used to build this module.
@@ -222,7 +208,6 @@ struct swiftscan_module_details_s {
   union {
     swiftscan_swift_textual_details_t swift_textual_details;
     swiftscan_swift_binary_details_t swift_binary_details;
-    swiftscan_swift_placeholder_details_t swift_placeholder_details;
     swiftscan_clang_details_t clang_details;
   };
 };

include/swift/DependencyScan/DependencyScanningTool.h

@@ -68,14 +68,12 @@ class DependencyScanningTool {
   /// Construct a dependency scanning tool.
   DependencyScanningTool();
 
-  /// Collect the full module dependency graph for the input, ignoring any
-  /// placeholder modules.
+  /// Collect the full module dependency graph for the input.
   ///
   /// \returns a \c StringError with the diagnostic output if errors
   /// occurred, \c swiftscan_dependency_result_t otherwise.
   llvm::ErrorOr<swiftscan_dependency_graph_t>
   getDependencies(ArrayRef<const char *> Command,
-                  const llvm::StringSet<> &PlaceholderModules,
                   StringRef WorkingDirectory);
 
   /// Collect the set of imports for the input module

include/swift/DependencyScan/SerializedModuleDependencyCacheFormat.h

@@ -39,7 +39,7 @@ using llvm::BCVBR;
 
 /// Every .moddepcache file begins with these 4 bytes, for easy identification.
 const unsigned char MODULE_DEPENDENCY_CACHE_FORMAT_SIGNATURE[] = {'I', 'M', 'D','C'};
-const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MAJOR = 9;
+const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MAJOR = 10;
 /// Increment this on every change.
 const unsigned MODULE_DEPENDENCY_CACHE_FORMAT_VERSION_MINOR = 3;
 
@@ -109,7 +109,6 @@ enum {
   OPTIONAL_IMPORT_STATEMENT_ARRAY_NODE,
   SWIFT_INTERFACE_MODULE_DETAILS_NODE,
   SWIFT_SOURCE_MODULE_DETAILS_NODE,
-  SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE,
   SWIFT_BINARY_MODULE_DETAILS_NODE,
   CLANG_MODULE_DETAILS_NODE,
   IDENTIFIER_NODE,
@@ -204,7 +203,6 @@ using OptionalImportStatementArrayLayout =
 // - SwiftInterfaceModuleDetails
 // - SwiftSourceModuleDetails
 // - SwiftBinaryModuleDetails
-// - SwiftPlaceholderModuleDetails
 // - ClangModuleDetails
 using ModuleInfoLayout =
     BCRecordLayout<MODULE_NODE,                    // ID
@@ -269,13 +267,6 @@ using SwiftBinaryModuleDetailsLayout =
                    IdentifierIDField                 // UserModuleVersion
                    >;
 
-using SwiftPlaceholderModuleDetailsLayout =
-    BCRecordLayout<SWIFT_PLACEHOLDER_MODULE_DETAILS_NODE, // ID
-                   FileIDField,                           // compiledModulePath
-                   FileIDField,                           // moduleDocPath
-                   FileIDField                            // moduleSourceInfoPath
-                   >;
-
 using ClangModuleDetailsLayout =
     BCRecordLayout<CLANG_MODULE_DETAILS_NODE, // ID
                    FileIDField,               // pcmOutputPath

include/swift/Option/FrontendOptions.td

@@ -258,10 +258,6 @@ def const_gather_protocols_file
   : Separate<["-"], "const-gather-protocols-file">, MetaVarName<"<path>">,
     HelpText<"Specify a list of protocols for extraction of conformances' const values'">;
 
-def placeholder_dependency_module_map
-  : Separate<["-"], "placeholder-dependency-module-map-file">, MetaVarName<"<path>">,
-    HelpText<"Specify a JSON file containing information of external Swift module dependencies">;
-
 def import_prescan : Flag<["-"], "import-prescan">,
    HelpText<"When performing a dependency scan, only identify all imports of the main Swift module sources">;
 

include/swift/Serialization/ScanningLoaders.h

@@ -83,51 +83,6 @@ class SwiftModuleScanner : public SerializedModuleLoaderBase {
     return MDS->getKind() == MDS_plain;
   }
 };
-
-/// A ModuleLoader that loads placeholder dependency module stubs specified in
-/// -placeholder-dependency-module-map-file
-/// This loader is used only in dependency scanning to inform the scanner that a
-/// set of modules constitute placeholder dependencies that are not visible to
-/// the scanner but will nevertheless be provided by the scanner's clients. This
-/// "loader" will not attempt to load any module files.
-class PlaceholderSwiftModuleScanner : public SwiftModuleScanner {
-  /// Scan the given placeholder module map
-  void parsePlaceholderModuleMap(StringRef fileName);
-
-  llvm::StringMap<ExplicitSwiftModuleInputInfo> PlaceholderDependencyModuleMap;
-  llvm::BumpPtrAllocator Allocator;
-
-public:
-  PlaceholderSwiftModuleScanner(ASTContext &ctx, ModuleLoadingMode LoadMode,
-                                Identifier moduleName,
-                                StringRef PlaceholderDependencyModuleMap,
-                                InterfaceSubContextDelegate &astDelegate,
-                                StringRef moduleOutputPath,
-                                StringRef sdkModuleOutputPath)
-      : SwiftModuleScanner(ctx, LoadMode, moduleName, astDelegate,
-                           moduleOutputPath, sdkModuleOutputPath, {},
-                           MDS_placeholder) {
-    // FIXME: Find a better place for this map to live, to avoid
-    // doing the parsing on every module.
-    if (!PlaceholderDependencyModuleMap.empty()) {
-      parsePlaceholderModuleMap(PlaceholderDependencyModuleMap);
-    }
-  }
-
-  virtual bool
-  findModule(ImportPath::Element moduleID,
-             SmallVectorImpl<char> *moduleInterfacePath,
-             SmallVectorImpl<char> *moduleInterfaceSourcePath,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleBuffer,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleDocBuffer,
-             std::unique_ptr<llvm::MemoryBuffer> *moduleSourceInfoBuffer,
-             bool skipBuildingInterface, bool isTestableDependencyLookup,
-             bool &isFramework, bool &isSystemModule) override;
-
-  static bool classof(const SwiftModuleScanner *MDS) {
-    return MDS->getKind() == MDS_placeholder;
-  }
-};
 } // namespace swift
 
 #endif // SWIFT_SCANNINGLOADERS_H

lib/AST/ModuleDependencies.cpp

@@ -36,7 +36,7 @@ ModuleDependencyInfoStorageBase::~ModuleDependencyInfoStorageBase() {}
 
 bool ModuleDependencyInfo::isSwiftModule() const {
   return isSwiftInterfaceModule() || isSwiftSourceModule() ||
-         isSwiftBinaryModule() || isSwiftPlaceholderModule();
+         isSwiftBinaryModule();
 }
 
 bool ModuleDependencyInfo::isTextualSwiftModule() const {
@@ -66,10 +66,6 @@ bool ModuleDependencyInfo::isSwiftBinaryModule() const {
   return isa<SwiftBinaryModuleDependencyStorage>(storage.get());
 }
 
-bool ModuleDependencyInfo::isSwiftPlaceholderModule() const {
-  return isa<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-}
-
 bool ModuleDependencyInfo::isClangModule() const {
   return isa<ClangModuleDependencyStorage>(storage.get());
 }
@@ -97,12 +93,6 @@ ModuleDependencyInfo::getAsClangModule() const {
   return dyn_cast<ClangModuleDependencyStorage>(storage.get());
 }
 
-/// Retrieve the dependencies for a placeholder dependency module stub.
-const SwiftPlaceholderModuleDependencyStorage *
-ModuleDependencyInfo::getAsPlaceholderDependencyModule() const {
-  return dyn_cast<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-}
-
 void ModuleDependencyInfo::addTestableImport(ImportPath::Module module) {
   assert(getAsSwiftSourceModule() && "Expected source module for addTestableImport.");
   dyn_cast<SwiftSourceModuleDependenciesStorage>(storage.get())->addTestableImport(module);
@@ -361,11 +351,6 @@ std::string ModuleDependencyInfo::getModuleOutputPath() const {
         cast<SwiftBinaryModuleDependencyStorage>(storage.get());
     return swiftBinaryStorage->compiledModulePath;
   }
-  case swift::ModuleDependencyKind::SwiftPlaceholder: {
-    auto swiftPlaceholderStorage =
-        cast<SwiftPlaceholderModuleDependencyStorage>(storage.get());
-    return swiftPlaceholderStorage->compiledModulePath;
-  }
   default:
     llvm_unreachable("Unexpected dependency kind");
   }
@@ -849,8 +834,6 @@ ModuleDependenciesCache::findSwiftDependency(StringRef moduleName) const {
     return found;
   if (auto found = findDependency(moduleName, ModuleDependencyKind::SwiftSource))
     return found;
-  if (auto found = findDependency(moduleName, ModuleDependencyKind::SwiftPlaceholder))
-    return found;
   return std::nullopt;
 }
 

lib/AST/ModuleLoader.cpp

@@ -240,9 +240,6 @@ ModuleDependencyInfo::collectCrossImportOverlayNames(
     case swift::ModuleDependencyKind::SwiftSource: {
       return result;
     }
-    case swift::ModuleDependencyKind::SwiftPlaceholder: {
-      return result;
-    }
     case swift::ModuleDependencyKind::LastKind:
       llvm_unreachable("Unhandled dependency kind.");
   }