[cxx-interop] Add flag to set minimum access level for reverse interop

include/swift/AST/DiagnosticsFrontend.def

@@ -612,6 +612,11 @@ ERROR(package_cmo_requires_library_evolution, none,
 WARNING(internal_bridging_header_without_library_evolution,none,
         "using internal bridging headers without library evolution can cause instability", ())
 
+ERROR(error_invalid_clang_header_access_level, none,
+      "invalid minimum clang header access level '%0'; chose from "
+      "'public'|'package'|'internal'",
+      (StringRef))
+
 ERROR(experimental_not_supported_in_production,none,
       "experimental feature '%0' cannot be enabled in production compiler",
       (StringRef))

include/swift/Frontend/FrontendOptions.h

@@ -13,6 +13,7 @@
 #ifndef SWIFT_FRONTEND_FRONTENDOPTIONS_H
 #define SWIFT_FRONTEND_FRONTENDOPTIONS_H
 
+#include "swift/AST/AttrKind.h"
 #include "swift/Basic/FileTypes.h"
 #include "swift/Basic/PathRemapper.h"
 #include "swift/Basic/Version.h"
@@ -501,6 +502,10 @@ class FrontendOptions {
   /// header.
   std::optional<ClangHeaderExposeBehavior> ClangHeaderExposedDecls;
 
+  // Include declarations that are at least as visible as the acces specified
+  // by -emit-clang-header-min-access
+  std::optional<AccessLevel> ClangHeaderMinAccess;
+
   struct ClangHeaderExposedImportedModule {
     std::string moduleName;
     std::string headerName;

include/swift/Option/Options.td

@@ -808,6 +808,11 @@ def emit_clang_header_path : Separate<["-"], "emit-clang-header-path">,
   HelpText<"Emit an Objective-C and C++ header file to <path>">,
   Alias<emit_objc_header_path>;
 
+def emit_clang_header_min_access : Separate<["-"], "emit-clang-header-min-access">,
+  Flags<[FrontendOption, NoInteractiveOption, ArgumentIsPath, CacheInvariant]>,
+  MetaVarName<"<access-level>">,
+  HelpText<"The minimum access level of declarations to include in the emitted header.>">;
+
 def static : Flag<["-"], "static">,
   Flags<[FrontendOption, ModuleInterfaceOption, NoInteractiveOption]>,
   HelpText<"Make this module statically linkable and make the output of -emit-library a static library.">;

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -14,7 +14,7 @@
 
 #include "ArgsToFrontendInputsConverter.h"
 #include "ArgsToFrontendOutputsConverter.h"
-#include "clang/Driver/Driver.h"
+#include "swift/AST/AttrKind.h"
 #include "swift/AST/DiagnosticsFrontend.h"
 #include "swift/Basic/Assertions.h"
 #include "swift/Basic/Platform.h"
@@ -24,18 +24,19 @@
 #include "swift/Parse/Lexer.h"
 #include "swift/Parse/ParseVersion.h"
 #include "swift/Strings.h"
+#include "clang/Driver/Driver.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/TargetParser/Triple.h"
 #include "llvm/CAS/ObjectStore.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/Compression.h"
-#include "llvm/Support/PrefixMapper.h"
-#include "llvm/Support/Process.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/LineIterator.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/PrefixMapper.h"
+#include "llvm/Support/Process.h"
+#include "llvm/TargetParser/Triple.h"
 
 using namespace swift;
 using namespace llvm::opt;
@@ -399,6 +400,17 @@ bool ArgsToFrontendOptionsConverter::convert(
                       HasExposeAttrOrImplicitDeps)
             .Default(std::nullopt);
   }
+  if (const Arg *A = Args.getLastArg(OPT_emit_clang_header_min_access)) {
+    Opts.ClangHeaderMinAccess =
+        llvm::StringSwitch<std::optional<AccessLevel>>(A->getValue())
+            .Case("public", AccessLevel::Public)
+            .Case("package", AccessLevel::Package)
+            .Case("internal", AccessLevel::Internal)
+            .Default(std::nullopt);
+    if (!Opts.ClangHeaderMinAccess)
+      Diags.diagnose(SourceLoc(), diag::error_invalid_clang_header_access_level,
+                     A->getValue());
+  }
   for (const auto &arg :
        Args.getAllArgValues(options::OPT_clang_header_expose_module)) {
     auto splitArg = StringRef(arg).split('=');

lib/PrintAsClang/ModuleContentsWriter.cpp

@@ -20,6 +20,7 @@
 #include "PrintSwiftToClangCoreScaffold.h"
 #include "SwiftToClangInteropContext.h"
 
+#include "swift/AST/AttrKind.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/DiagnosticsSema.h"
 #include "swift/AST/ExistentialLayout.h"
@@ -1151,35 +1152,41 @@ class ModuleWriter {
 };
 } // end anonymous namespace
 
-static AccessLevel getRequiredAccess(const ModuleDecl &M) {
-  return M.isExternallyConsumed() ? AccessLevel::Public : AccessLevel::Internal;
+static AccessLevel getRequiredAccess(const ModuleDecl &M,
+                                     AccessLevel minAccess) {
+  return M.isExternallyConsumed() ? minAccess : AccessLevel::Internal;
 }
 
 void swift::printModuleContentsAsObjC(
     raw_ostream &os, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
-    ModuleDecl &M, SwiftToClangInteropContext &interopContext) {
+    ModuleDecl &M, SwiftToClangInteropContext &interopContext,
+    AccessLevel minAccess) {
   llvm::raw_null_ostream prologueOS;
   llvm::StringSet<> exposedModules;
-  ModuleWriter(os, prologueOS, imports, M, interopContext, getRequiredAccess(M),
+  ModuleWriter(os, prologueOS, imports, M, interopContext,
+               getRequiredAccess(M, minAccess),
                /*requiresExposedAttribute=*/false, exposedModules,
                OutputLanguageMode::ObjC)
       .write();
 }
 
 void swift::printModuleContentsAsC(
     raw_ostream &os, llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
-    ModuleDecl &M, SwiftToClangInteropContext &interopContext) {
+    ModuleDecl &M, SwiftToClangInteropContext &interopContext,
+    AccessLevel minAccess) {
   llvm::raw_null_ostream prologueOS;
   llvm::StringSet<> exposedModules;
-  ModuleWriter(os, prologueOS, imports, M, interopContext, getRequiredAccess(M),
+  ModuleWriter(os, prologueOS, imports, M, interopContext,
+               getRequiredAccess(M, minAccess),
                /*requiresExposedAttribute=*/false, exposedModules,
                OutputLanguageMode::C)
       .write();
 }
 
 EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
     raw_ostream &os, ModuleDecl &M, SwiftToClangInteropContext &interopContext,
-    bool requiresExposedAttribute, llvm::StringSet<> &exposedModules) {
+    AccessLevel minAccess, bool requiresExposedAttribute,
+    llvm::StringSet<> &exposedModules) {
   std::string moduleContentsBuf;
   llvm::raw_string_ostream moduleOS{moduleContentsBuf};
   std::string modulePrologueBuf;
@@ -1197,8 +1204,8 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
 
   // FIXME: Use getRequiredAccess once @expose is supported.
   ModuleWriter writer(moduleOS, prologueOS, info.imports, M, interopContext,
-                      AccessLevel::Public, requiresExposedAttribute,
-                      exposedModules, OutputLanguageMode::Cxx);
+                      minAccess, requiresExposedAttribute, exposedModules,
+                      OutputLanguageMode::Cxx);
   writer.write();
   info.dependsOnStandardLibrary = writer.isStdlibRequired();
   if (M.isStdlibModule()) {

lib/PrintAsClang/ModuleContentsWriter.h

@@ -35,12 +35,14 @@ using ImportModuleTy = PointerUnion<ModuleDecl*, const clang::Module*>;
 void printModuleContentsAsObjC(raw_ostream &os,
                                llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
                                ModuleDecl &M,
-                               SwiftToClangInteropContext &interopContext);
+                               SwiftToClangInteropContext &interopContext,
+                               AccessLevel minAccess);
 
 void printModuleContentsAsC(raw_ostream &os,
                             llvm::SmallPtrSetImpl<ImportModuleTy> &imports,
                             ModuleDecl &M,
-                            SwiftToClangInteropContext &interopContext);
+                            SwiftToClangInteropContext &interopContext,
+                            AccessLevel minAccess);
 
 struct EmittedClangHeaderDependencyInfo {
     /// The set of imported modules used by this module.
@@ -52,9 +54,11 @@ struct EmittedClangHeaderDependencyInfo {
 /// Prints the declarations of \p M to \p os in C++ language mode.
 ///
 /// \returns Dependencies required by this module.
-EmittedClangHeaderDependencyInfo printModuleContentsAsCxx(
-    raw_ostream &os, ModuleDecl &M, SwiftToClangInteropContext &interopContext,
-    bool requiresExposedAttribute, llvm::StringSet<> &exposedModules);
+EmittedClangHeaderDependencyInfo
+printModuleContentsAsCxx(raw_ostream &os, ModuleDecl &M,
+                         SwiftToClangInteropContext &interopContext,
+                         AccessLevel minAccess, bool requiresExposedAttribute,
+                         llvm::StringSet<> &exposedModules);
 
 } // end namespace swift
 

lib/PrintAsClang/PrintAsClang.cpp

@@ -17,6 +17,7 @@
 #include "SwiftToClangInteropContext.h"
 
 #include "swift/AST/ASTContext.h"
+#include "swift/AST/AttrKind.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/PrettyStackTrace.h"
 #include "swift/Basic/Assertions.h"
@@ -620,7 +621,9 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
   if (M->getASTContext().LangOpts.hasFeature(Feature::CDecl)) {
     SmallPtrSet<ImportModuleTy, 8> imports;
     llvm::raw_string_ostream cModuleContents{moduleContentsScratch};
-    printModuleContentsAsC(cModuleContents, imports, *M, interopContext);
+    printModuleContentsAsC(
+        cModuleContents, imports, *M, interopContext,
+        frontendOpts.ClangHeaderMinAccess.value_or(AccessLevel::Public));
 
     llvm::StringMap<StringRef> exposedModuleHeaderNames;
     writeImports(os, imports, *M, bridgingHeader, frontendOpts,
@@ -634,7 +637,9 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
   // Objective-C content
   SmallPtrSet<ImportModuleTy, 8> imports;
   llvm::raw_string_ostream objcModuleContents{moduleContentsScratch};
-  printModuleContentsAsObjC(objcModuleContents, imports, *M, interopContext);
+  printModuleContentsAsObjC(
+      objcModuleContents, imports, *M, interopContext,
+      frontendOpts.ClangHeaderMinAccess.value_or(AccessLevel::Public));
   emitObjCConditional(os, [&] {
     llvm::StringMap<StringRef> exposedModuleHeaderNames;
     writeImports(os, imports, *M, bridgingHeader, frontendOpts,
@@ -685,6 +690,7 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
     llvm::raw_string_ostream moduleContents{moduleContentsBuf};
     auto deps = printModuleContentsAsCxx(
         moduleContents, *M, interopContext,
+        frontendOpts.ClangHeaderMinAccess.value_or(AccessLevel::Public),
         /*requiresExposedAttribute=*/requiresExplicitExpose, exposedModules);
     // FIXME: In ObjC++ mode, we do not need to reimport duplicate modules.
     llvm::StringMap<StringRef> exposedModuleHeaderNames;
@@ -701,9 +707,10 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
       auto macroGuard = computeMacroGuard(M->getASTContext().getStdlibModule());
       os << "#ifndef " << macroGuard << "\n";
       os << "#define " << macroGuard << "\n";
-      printModuleContentsAsCxx(
-          os, *M->getASTContext().getStdlibModule(), interopContext,
-          /*requiresExposedAttribute=*/true, exposedModules);
+      printModuleContentsAsCxx(os, *M->getASTContext().getStdlibModule(),
+                               interopContext, AccessLevel::Public,
+                               /*requiresExposedAttribute=*/true,
+                               exposedModules);
       os << "#endif // " << macroGuard << "\n";
     }
 

lib/PrintAsClang/SwiftToClangInteropContext.cpp

@@ -20,7 +20,7 @@ SwiftToClangInteropContext::SwiftToClangInteropContext(
     ModuleDecl &mod, const IRGenOptions &irGenOpts)
     : mod(mod), irGenOpts(irGenOpts) {}
 
-SwiftToClangInteropContext::~SwiftToClangInteropContext() {}
+SwiftToClangInteropContext::~SwiftToClangInteropContext() = default;
 
 IRABIDetailsProvider &SwiftToClangInteropContext::getIrABIDetails() {
   if (!irABIDetails)

test/Interop/SwiftToCxx/core/set-min-access-level-and-expose-explicitly.swift

@@ -0,0 +1,46 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=has-expose-attr -emit-clang-header-min-access public -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-PUBLIC < %t/core.h
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=has-expose-attr -emit-clang-header-min-access package -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-PACKAGE < %t/core.h
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=has-expose-attr -emit-clang-header-min-access internal -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-INTERNAL < %t/core.h
+
+@_expose(Cxx)
+public func publicFunc(_ x: Int) -> Int {
+    return x
+}
+
+@_expose(Cxx)
+package func packageFunc(_ x: Int) -> Int {
+    return x
+}
+
+@_expose(Cxx)
+internal func internalFunc(_ x: Int) -> Int {
+    return x
+}
+
+@_expose(Cxx)
+private func privateFunc(_ x: Int) -> Int {
+    return x
+}
+
+// CHECK-PUBLIC-NOT: internalFunc
+// CHECK-PUBLIC-NOT: packageFunc
+// CHECK-PUBLIC-NOT: privateFunc
+// CHECK-PUBLIC: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+
+// CHECK-PACKAGE-NOT: internalFunc
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int packageFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core11packageFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-PACKAGE-NOT: privateFunc
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int internalFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core12internalFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int packageFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core11packageFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-INTERNAL-NOT: privateFunc
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {

test/Interop/SwiftToCxx/core/set-min-access-level.swift

@@ -0,0 +1,79 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=all-public -emit-clang-header-min-access public -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-PUBLIC < %t/core.h
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=all-public -emit-clang-header-min-access package -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-PACKAGE < %t/core.h
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -module-name Core -typecheck -verify -emit-clang-header-path %t/core.h -clang-header-expose-decls=all-public -emit-clang-header-min-access internal -package-name Core
+// RUN: %FileCheck %s --check-prefix CHECK-INTERNAL < %t/core.h
+
+// RUN: %empty-directory(%t)
+// RUN: not %target-swift-frontend %s -module-name Core -typecheck -emit-clang-header-path %t/core.h -clang-header-expose-decls=all-public -emit-clang-header-min-access inernal -package-name Core 2>&1 | %FileCheck %s --check-prefix CHECK-DIAGNOSTIC
+
+public func publicFunc(_ x: Int) -> Int {
+    return x
+}
+
+package func packageFunc(_ x: Int) -> Int {
+    return x
+}
+
+internal func internalFunc(_ x: Int) -> Int {
+    return x
+}
+
+private func privateFunc(_ x: Int) -> Int {
+    return x
+}
+
+public struct S {
+    public func publicMethod(_ x: Int) -> Int {
+        return x
+    }
+
+    package func packageMethod(_ x: Int) -> Int {
+        return x
+    }
+
+    internal func internalMethod(_ x: Int) -> Int {
+        return x
+    }
+
+    private func privateMethod(_ x: Int) -> Int {
+        return x
+    }
+
+    private var x: Int
+}
+
+// CHECK-PUBLIC-NOT: internalFunc
+// CHECK-PUBLIC-NOT: packageFunc
+// CHECK-PUBLIC-NOT: privateFunc
+// CHECK-PUBLIC: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-PUBLIC: SWIFT_INLINE_THUNK swift::Int S::publicMethod(swift::Int x) const {
+// CHECK-PUBLIC-NOT: packageMethod
+// CHECK-PUBLIC-NOT: internalMethod
+// CHECK-PUBLIC-NOT: privateMethod
+
+// CHECK-PACKAGE-NOT: internalFunc
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int packageFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core11packageFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-PACKAGE-NOT: privateFunc
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int S::publicMethod(swift::Int x) const {
+// CHECK-PACKAGE: SWIFT_INLINE_THUNK swift::Int S::packageMethod(swift::Int x) const {
+// CHECK-PACKAGE-NOT: internalMethod
+// CHECK-PACKAGE-NOT: privateMethod
+
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int internalFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core12internalFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int packageFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core11packageFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-INTERNAL-NOT: privateFunc
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int publicFunc(swift::Int x) noexcept SWIFT_SYMBOL("s:4Core10publicFuncyS2iF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int S::publicMethod(swift::Int x) const {
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int S::packageMethod(swift::Int x) const {
+// CHECK-INTERNAL: SWIFT_INLINE_THUNK swift::Int S::internalMethod(swift::Int x) const {
+// CHECK-INTERNAL-NOT: privateMethod
+
+// CHECK-DIAGNOSTIC: error: invalid minimum clang header access level 'inernal'; chose from 'public'|'package'|'internal'