AST: Use availability to control decl visibility in public swiftinterfaces.

Declarations that are unavailable at runtime because of an `@available`
attribute referencing a custom domain that was imported `@_spiOnly` should be
hidden from public swiftinterface files in `-library-level=api` modules. For
remaining declarations that do get printed in the public swiftinterface, skip
printing any `@available` attribute that refers to the domains from those
`@_spiOnly` dependencies. This allows API developers to control declaration
visibility using availability defined by another module.

Resolves rdar://156512028.

lib/AST/ASTPrinter.cpp

@@ -20,6 +20,8 @@
 #include "swift/AST/ASTMangler.h"
 #include "swift/AST/ASTVisitor.h"
 #include "swift/AST/Attr.h"
+#include "swift/AST/AvailabilityConstraint.h"
+#include "swift/AST/AvailabilityContext.h"
 #include "swift/AST/Builtins.h"
 #include "swift/AST/ClangModuleLoader.h"
 #include "swift/AST/Comment.h"
@@ -189,6 +191,38 @@ static bool shouldPrintAllSemanticDetails(const PrintOptions &options) {
   return false;
 }
 
+static bool shouldSkipDeclInPublicInterface(const Decl *D) {
+  // @_spi should be skipped in the public interface.
+  if (D->isSPI())
+    return true;
+
+  // Decls that are unavailable at runtime in an availability domain that has
+  // been @_spiOnly imported should be hidden from the public interface of
+  // a -library-level=api module.
+  auto &ctx = D->getDeclContext()->getASTContext();
+  if (ctx.LangOpts.LibraryLevel != LibraryLevel::API)
+    return false;
+
+  auto *SF = D->getDeclContext()->getParentSourceFile();
+  if (!SF)
+    return false;
+
+  auto constraints = getAvailabilityConstraintsForDecl(
+      D, AvailabilityContext::forDeploymentTarget(ctx));
+  llvm::SmallVector<AvailabilityDomain, 4> unavailableDomains;
+  getRuntimeUnavailableDomains(constraints, unavailableDomains, ctx);
+
+  for (auto domain : unavailableDomains) {
+    if (auto *domainDecl = domain.getDecl()) {
+      if (SF->getRestrictedImportKind(domainDecl->getModuleContext()) ==
+          RestrictedImportKind::SPIOnly)
+        return true;
+    }
+  }
+
+  return false;
+}
+
 /// Get the non-recursive printing options that should be applied when
 /// printing the type of a value decl.
 static NonRecursivePrintOptions getNonRecursiveOptions(const ValueDecl *D) {
@@ -293,8 +327,7 @@ PrintOptions PrintOptions::printSwiftInterfaceFile(ModuleDecl *ModuleToPrint,
       if (D->getAttrs().hasAttribute<ImplementationOnlyAttr>())
         return false;
 
-      // Skip SPI decls if `PrintSPIs`.
-      if (options.printPublicInterface() && D->isSPI())
+      if (options.printPublicInterface() && shouldSkipDeclInPublicInterface(D))
         return false;
 
       if (auto *VD = dyn_cast<ValueDecl>(D)) {
@@ -410,8 +443,6 @@ PrintOptions PrintOptions::printSwiftInterfaceFile(ModuleDecl *ModuleToPrint,
   result.CurrentPrintabilityChecker =
       std::make_shared<ShouldPrintForModuleInterface>();
 
-  // FIXME: We don't really need 'public' on everything; we could just change
-  // the default to 'public' and mark the 'internal' things.
   result.PrintAccess = true;
 
   result.ExcludeAttrList = {

lib/AST/Attr.cpp

@@ -805,6 +805,7 @@ void DeclAttributes::print(ASTPrinter &Printer, const PrintOptions &Options,
   AttributeVector modifiers;
   bool libraryLevelAPI =
       D && D->getASTContext().LangOpts.LibraryLevel == LibraryLevel::API;
+  auto *SF = D ? D->getDeclContext()->getParentSourceFile() : nullptr;
 
   for (auto DA : llvm::reverse(FlattenedAttrs)) {
     // Don't skip implicit custom attributes. Custom attributes like global
@@ -849,6 +850,16 @@ void DeclAttributes::print(ASTPrinter &Printer, const PrintOptions &Options,
       if (!semanticAttr)
         continue;
 
+      // In the public interfaces of -library-level=api modules, skip @available
+      // attributes that refer to domains imported from @_spiOnly modules.
+      if (Options.printPublicInterface() && libraryLevelAPI) {
+        if (auto *domainDecl = semanticAttr->getDomain().getDecl()) {
+          if (SF->getRestrictedImportKind(domainDecl->getModuleContext()) ==
+              RestrictedImportKind::SPIOnly)
+            continue;
+        }
+      }
+
       if (isShortAvailable(*semanticAttr)) {
         if (semanticAttr->isSwiftLanguageModeSpecific())
           swiftVersionAvailableAttribute.emplace(*semanticAttr);

lib/AST/Module.cpp

@@ -2879,6 +2879,7 @@ bool SourceFile::hasTestableOrPrivateImport(
       });
 }
 
+// FIXME: This should probably be requestified.
 RestrictedImportKind SourceFile::getRestrictedImportKind(const ModuleDecl *module) const {
   auto &imports = getASTContext().getImportCache();
   RestrictedImportKind importKind = RestrictedImportKind::MissingImport;

lib/Sema/ResilienceDiagnostics.cpp

@@ -231,6 +231,8 @@ static bool shouldDiagnoseDeclAccess(const ValueDecl *D,
                                      const ExportContext &where) {
   auto reason = where.getExportabilityReason();
   auto DC = where.getDeclContext();
+  if (!reason)
+    return false;
 
   switch (*reason) {
   case ExportabilityReason::ExtensionWithPublicMembers:
@@ -304,6 +306,15 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
     break;
 
   case DisallowedOriginKind::SPIOnly:
+    // Availability attributes referring to availability domains from modules
+    // that are imported @_spiOnly in a -library-level=api will not be printed
+    // in the public swiftinterface of the module and should therefore not be
+    // diagnosed for exportability.
+    if (reason && reason == ExportabilityReason::AvailableAttribute &&
+        ctx.LangOpts.LibraryLevel == LibraryLevel::API)
+      return false;
+    break;
+
   case DisallowedOriginKind::ImplementationOnly:
   case DisallowedOriginKind::SPIImported:
   case DisallowedOriginKind::SPILocal:

test/Inputs/custom-modules/availability-domains/Lakes.h

@@ -1,6 +1,10 @@
 #include <availability_domain.h>
 
+int huron_pred(void);
+
 CLANG_ENABLED_AVAILABILITY_DOMAIN(Salt);
+CLANG_DISABLED_AVAILABILITY_DOMAIN(Erie);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(Huron, huron_pred);
 
 #define AVAIL 0
 #define UNAVAIL 1

test/Inputs/custom-modules/availability-domains/Seas.h

@@ -1,7 +1,10 @@
 #include <availability_domain.h>
 
+int aegean_pred(void);
+
 CLANG_ENABLED_AVAILABILITY_DOMAIN(Baltic);
 CLANG_DISABLED_AVAILABILITY_DOMAIN(Mediterranean);
+CLANG_DYNAMIC_AVAILABILITY_DOMAIN(Aegean, aegean_pred);
 
 #define AVAIL 0
 #define UNAVAIL 1

test/ModuleInterface/availability_custom_domains_library_level_api.swift

@@ -0,0 +1,120 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -emit-module %s \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -enable-experimental-feature CustomAvailability \
+// RUN:   -experimental-spi-only-imports \
+// RUN:   -enable-library-evolution -swift-version 5 -library-level api \
+// RUN:   -package-name TestPackage -module-name Test \
+// RUN:   -emit-module-interface-path %t/Test.swiftinterface \
+// RUN:   -emit-private-module-interface-path %t/Test.private.swiftinterface \
+// RUN:   -emit-package-module-interface-path %t/Test.package.swiftinterface
+
+// RUN: %target-swift-typecheck-module-from-interface(%t/Test.swiftinterface) \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -module-name Test
+
+// RUN: %target-swift-typecheck-module-from-interface(%t/Test.private.swiftinterface) \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -module-name Test
+
+// RUN: %target-swift-typecheck-module-from-interface(%t/Test.package.swiftinterface) \
+// RUN:   -I %S/../Inputs/custom-modules/availability-domains \
+// RUN:   -module-name Test
+
+// RUN: %FileCheck %s --check-prefixes=CHECK --input-file %t/Test.swiftinterface
+// RUN: %FileCheck %s --check-prefixes=CHECK-PUBLIC --input-file %t/Test.swiftinterface
+// RUN: %FileCheck %s --check-prefixes=CHECK,CHECK-NONPUBLIC --input-file %t/Test.private.swiftinterface
+// RUN: %FileCheck %s --check-prefixes=CHECK,CHECK-NONPUBLIC --input-file %t/Test.package.swiftinterface
+
+// REQUIRES: swift_feature_CustomAvailability
+
+import Lakes
+@_spiOnly import Seas
+
+// CHECK:                 @available(Salt)
+// CHECK:                 public func availableInPublicEnabledDomain()
+@available(Salt)
+public func availableInPublicEnabledDomain() { }
+
+// CHECK:                 @available(Erie)
+// CHECK:                 public func availableInPublicDisabledDomain()
+@available(Erie)
+public func availableInPublicDisabledDomain() { }
+
+// CHECK:                 @available(Huron)
+// CHECK:                 public func availableInPublicDynamicDomain()
+@available(Huron)
+public func availableInPublicDynamicDomain() { }
+
+// CHECK:                 @available(Salt, unavailable)
+// CHECK:                 public func unavailableInPublicEnabledDomain()
+@available(Salt, unavailable)
+public func unavailableInPublicEnabledDomain() { }
+
+// CHECK:                 @available(Erie, unavailable)
+// CHECK:                 public func unavailableInPublicDisabledDomain()
+@available(Erie, unavailable)
+public func unavailableInPublicDisabledDomain() { }
+
+// CHECK:                 @available(Huron, unavailable)
+// CHECK:                 public func unavailableInPublicDynamicDomain()
+@available(Huron, unavailable)
+public func unavailableInPublicDynamicDomain() { }
+
+// CHECK-NONPUBLIC:       @available(Baltic)
+// CHECK-PUBLIC-NOT:      Baltic
+// CHECK-LABEL:           public func availableInSPIOnlyEnabledDomain()
+@available(Baltic)
+public func availableInSPIOnlyEnabledDomain() { }
+
+// CHECK-NONPUBLIC:       @available(Mediterranean)
+// CHECK-NONPUBLIC-LABEL: public func availableInSPIOnlyDisabledDomain_Secret()
+// CHECK-PUBLIC-NOT:      Mediterranean
+// CHECK-PUBLIC-NOT:      availableInSPIOnlyDisabledDomain_Secret
+@available(Mediterranean)
+public func availableInSPIOnlyDisabledDomain_Secret() { }
+
+// CHECK-NONPUBLIC:       @available(Aegean)
+// CHECK-PUBLIC-NOT:      Aegean
+// CHECK-LABEL:           public func availableInSPIOnlyDynamicDomain()
+@available(Aegean)
+public func availableInSPIOnlyDynamicDomain() { }
+
+// CHECK-NONPUBLIC:       @available(Baltic, unavailable)
+// CHECK-NONPUBLIC-LABEL: public func unavailableInSPIOnlyEnabledDomain_Secret()
+// CHECK-PUBLIC-NOT:      Baltic
+// CHECK-PUBLIC-NOT:      unavailableInSPIOnlyEnabledDomain_Secret
+@available(Baltic, unavailable)
+public func unavailableInSPIOnlyEnabledDomain_Secret() { }
+
+// CHECK-NONPUBLIC:       @available(Mediterranean, unavailable)
+// CHECK-PUBLIC-NOT:      Mediterranean
+// CHECK-LABEL:           public func unavailableInSPIOnlyDisabledDomain()
+@available(Mediterranean, unavailable)
+public func unavailableInSPIOnlyDisabledDomain() { }
+
+// CHECK:                 @available(*, unavailable)
+// CHECK-NONPUBLIC:       @available(Baltic)
+// CHECK-PUBLIC-NOT:      Baltic
+// CHECK-LABEL:           public func availableInSPIOnlyEnabledDomainAndUnavailableUniversally()
+@available(*, unavailable)
+@available(Baltic)
+public func availableInSPIOnlyEnabledDomainAndUnavailableUniversally() { }
+
+// CHECK-NONPUBLIC:       @available(*, unavailable)
+// CHECK-NONPUBLIC:       @available(Mediterranean)
+// CHECK-NONPUBLIC-LABEL: public func availableInSPIOnlyDisabledDomainAndUnavailableUniversally_Secret()
+// CHECK-PUBLIC-NOT:      Mediterranean
+// CHECK-PUBLIC-NOT:      availableInSPIOnlyDisabledDomainAndUnavailableUniversally_Secret
+@available(*, unavailable)
+@available(Mediterranean)
+public func availableInSPIOnlyDisabledDomainAndUnavailableUniversally_Secret() { }
+
+// CHECK:                 @available(*, unavailable)
+// CHECK-NONPUBLIC:       @available(Aegean)
+// CHECK-PUBLIC-NOT:      Aegean
+// CHECK-LABEL:           public func availableInSPIOnlyDynamicDomainAndUnavailableUniversally()
+@available(*, unavailable)
+@available(Aegean)
+public func availableInSPIOnlyDynamicDomainAndUnavailableUniversally() { }