[interop][SwiftToCxx] do not require @_expose when generating C++ interface for a Swift module

Instead, we emit API bindings for all supported public APIs, when -enable-experimental-cxx-interop is enabled

Author: hyp

lib/PrintAsClang/PrintAsClang.cpp

@@ -563,13 +563,16 @@ bool swift::printAsClangHeader(raw_ostream &os, ModuleDecl *M,
     ClangSyntaxPrinter(os).printIncludeForShimHeader(
         "_SwiftCxxInteroperability.h");
 
+    // Explicit @expose attribute is required only when the user specifies
+    // -clang-header-expose-decls flag.
+    // FIXME: should we detect any presence of @expose and require it then?
     bool requiresExplicitExpose =
-        !frontendOpts.ClangHeaderExposedDecls.has_value() ||
-        *frontendOpts.ClangHeaderExposedDecls ==
-            FrontendOptions::ClangHeaderExposeBehavior::HasExposeAttr ||
-        *frontendOpts.ClangHeaderExposedDecls ==
-            FrontendOptions::ClangHeaderExposeBehavior::
-                HasExposeAttrOrImplicitDeps;
+        frontendOpts.ClangHeaderExposedDecls.has_value() &&
+        (*frontendOpts.ClangHeaderExposedDecls ==
+             FrontendOptions::ClangHeaderExposeBehavior::HasExposeAttr ||
+         *frontendOpts.ClangHeaderExposedDecls ==
+             FrontendOptions::ClangHeaderExposeBehavior::
+                 HasExposeAttrOrImplicitDeps);
     // Swift stdlib dependencies are emitted into the same header when
     // -clang-header-expose-decls flag is not specified, or when it allows
     // implicit dependency emission.

test/Interop/SwiftToCxx/functions/swift-expected-execution.cpp

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-frontend %S/swift-functions-errors.swift -typecheck -module-name Functions -Xcc -fno-exceptions -enable-experimental-cxx-interop -emit-clang-header-path %t/functions.h
+// RUN: %target-swift-frontend %S/swift-functions-errors.swift -typecheck -module-name Functions -Xcc -fno-exceptions -enable-experimental-cxx-interop -clang-header-expose-decls=has-expose-attr-or-stdlib -emit-clang-header-path %t/functions.h
 
 // RUN: %target-interop-build-clangxx -c %s -I %t -fno-exceptions -o %t/swift-expected-execution.o
 // RUN: %target-interop-build-swift %S/swift-functions-errors.swift -o %t/swift-expected-execution -Xlinker %t/swift-expected-execution.o -module-name Functions -Xfrontend -entry-point-function-name -Xfrontend swiftMain

test/Interop/SwiftToCxx/functions/swift-functions-errors-execution.cpp

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-frontend %S/swift-functions-errors.swift -typecheck -module-name Functions -enable-experimental-cxx-interop -emit-clang-header-path %t/functions.h
+// RUN: %target-swift-frontend %S/swift-functions-errors.swift -typecheck -module-name Functions -enable-experimental-cxx-interop -clang-header-expose-decls=has-expose-attr-or-stdlib  -emit-clang-header-path %t/functions.h
 
 // RUN: %target-interop-build-clangxx -c %s -I %t -o %t/swift-functions-errors-execution.o
 // RUN: %target-interop-build-swift %S/swift-functions-errors.swift -o %t/swift-functions-errors-execution -Xlinker %t/swift-functions-errors-execution.o -module-name Functions -Xfrontend -entry-point-function-name -Xfrontend swiftMain

test/Interop/SwiftToCxx/functions/swift-functions-errors.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend %s -typecheck -module-name Functions -enable-experimental-cxx-interop -emit-clang-header-path %t/functions.h
+// RUN: %target-swift-frontend %s -typecheck -module-name Functions -enable-experimental-cxx-interop -clang-header-expose-decls=has-expose-attr-or-stdlib -emit-clang-header-path %t/functions.h
 // RUN: %FileCheck %s < %t/functions.h
 
 // RUN: %check-interop-cxx-header-in-clang(%t/functions.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-function)

test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift

@@ -1,5 +1,5 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -parse-as-library %platform-module-dir/Swift.swiftmodule/%module-target-triple.swiftinterface -enable-library-evolution -disable-objc-attr-requires-foundation-module -typecheck -module-name Swift -parse-stdlib -enable-experimental-cxx-interop -emit-clang-header-path %t/Swift.h  -experimental-skip-all-function-bodies
+// RUN: %target-swift-frontend -parse-as-library %platform-module-dir/Swift.swiftmodule/%module-target-triple.swiftinterface -enable-library-evolution -disable-objc-attr-requires-foundation-module -typecheck -module-name Swift -parse-stdlib -enable-experimental-cxx-interop -clang-header-expose-decls=has-expose-attr-or-stdlib -emit-clang-header-path %t/Swift.h  -experimental-skip-all-function-bodies
 // RUN: %FileCheck %s < %t/Swift.h
 
 // RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-private-field -Wno-unused-function -Wc++98-compat-extra-semi)