Add IsSDKRelative field to ModuleInterfaceLayout

When serializing the module interface path of an interface that
is part of the SDK, we serialize relative to the SDK path. During
deserialization we need to know if a path was serialized relative
to the SDK or not. The existing logic assumes any relative path
has been serialized relative to the SDK, which makes it impossible
to compile modules from relative swiftinterface paths that are not
part of the SDK.

Update the swiftmodule file to include an attribute to show if the
path was serialized relative to the SDK or not, which is used
during deserialization to correctly reconstruct the interface path.

include/swift/Serialization/SerializationOptions.h

@@ -162,6 +162,7 @@ public:
   bool SkipNonExportableDecls = false;
   bool ExplicitModuleBuild = false;
   bool EnableSerializationRemarks = false;
+  bool IsInterfaceSDKRelative = false;
 };
 
 } // end namespace swift

lib/Frontend/ModuleInterfaceBuilder.cpp

@@ -291,9 +291,10 @@ std::error_code ExplicitModuleInterfaceBuilder::buildSwiftModuleFromInterface(
   StringRef SDKPath = Instance.getASTContext().SearchPathOpts.getSDKPath();
 
   auto SDKRelativePath = getRelativeDepPath(InPath, SDKPath);
-  if (SDKRelativePath.has_value())
+  if (SDKRelativePath.has_value()) {
     SerializationOpts.ModuleInterface = SDKRelativePath.value();
-  else
+    SerializationOpts.IsInterfaceSDKRelative = true;
+  } else
     SerializationOpts.ModuleInterface = InPath;
 
   SerializationOpts.SDKName = Instance.getASTContext().LangOpts.SDKName;

lib/Serialization/ModuleFileSharedCore.cpp

@@ -1615,6 +1615,8 @@ ModuleFileSharedCore::ModuleFileSharedCore(
           break;
         }
         case input_block::MODULE_INTERFACE_PATH: {
+          input_block::ModuleInterfaceLayout::readRecord(
+              scratch, IsModuleInterfaceSDKRelative);
           ModuleInterfacePath = blobData;
           break;
         }
@@ -1837,10 +1839,12 @@ bool ModuleFileSharedCore::hasSourceInfo() const {
 std::string ModuleFileSharedCore::resolveModuleDefiningFilePath(const StringRef SDKPath) const {
   if (!ModuleInterfacePath.empty()) {
     std::string interfacePath = ModuleInterfacePath.str();
-    if (llvm::sys::path::is_relative(interfacePath) && !ModuleInterfacePath.starts_with(SDKPath)) {
-      SmallString<128> absoluteInterfacePath(SDKPath);
-      llvm::sys::path::append(absoluteInterfacePath, interfacePath);
-      return absoluteInterfacePath.str().str();
+    if (IsModuleInterfaceSDKRelative &&
+        !ModuleInterfacePath.starts_with(SDKPath) &&
+        llvm::sys::path::is_relative(interfacePath)) {
+      SmallString<128> resolvedPath(SDKPath);
+      llvm::sys::path::append(resolvedPath, interfacePath);
+      return resolvedPath.str().str();
     } else
       return interfacePath;
   } else

lib/Serialization/ModuleFileSharedCore.h

@@ -74,6 +74,9 @@ class ModuleFileSharedCore {
   /// Empty if this module didn't come from an interface file.
   StringRef ModuleInterfacePath;
 
+  /// true if this module interface was serialized relative to the SDK path.
+  bool IsModuleInterfaceSDKRelative = false;
+
   /// The module interface path if this module is adjacent to such an interface
   /// or it was itself compiled from an interface. Empty otherwise.
   StringRef CorrespondingInterfacePath;

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 904; // @available renamed decl ID removed
+const uint16_t SWIFTMODULE_VERSION_MINOR = 905; // IsModuleInterfaceSDKRelative
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1158,7 +1158,8 @@ namespace input_block {
 
   using ModuleInterfaceLayout = BCRecordLayout<
     MODULE_INTERFACE_PATH,
-    BCBlob // file path
+    BCFixed<1>, // SDK-relative?
+    BCBlob      // file path
   >;
 
 }

lib/Serialization/Serialization.cpp

@@ -1352,7 +1352,8 @@ void Serializer::writeInputBlock() {
   }
 
   if (!Options.ModuleInterface.empty())
-    ModuleInterface.emit(ScratchRecord, Options.ModuleInterface);
+    ModuleInterface.emit(ScratchRecord, Options.IsInterfaceSDKRelative,
+                         Options.ModuleInterface);
 
   SmallVector<ExternalMacroPlugin> macros;
   M->getExternalMacros(macros);

test/ModuleInterface/Inputs/relative_path/A.swiftmodule/arm64-apple-macos.swiftinterface

@@ -0,0 +1,8 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -target arm64-apple-macosx15.0 -module-name A
+
+import B
+
+public struct AStruct {
+    var y : BStruct
+}

test/ModuleInterface/Inputs/relative_path/B.swiftmodule/arm64-apple-macos.swiftinterface

@@ -0,0 +1,9 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -target arm64-apple-macosx15.0 -module-name B
+
+import Swift
+
+public struct BStruct {
+    var x : Int
+    public init()
+}

test/ModuleInterface/relative-interface-path.swift

@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t.relative_interface_path)
+// RUN: cp -R %S/Inputs/relative_path %t.relative_interface_path/
+// RUN: cd %t.relative_interface_path
+// RUN: mkdir out
+
+// RUN: %target-swift-frontend -target arm64-apple-macosx15.0 -compile-module-from-interface \
+// RUN:   relative_path/B.swiftmodule/arm64-apple-macos.swiftinterface -o out/B.swiftmodule
+// RUN: %target-swift-frontend -target arm64-apple-macosx15.0 -compile-module-from-interface \
+// RUN:   relative_path/A.swiftmodule/arm64-apple-macos.swiftinterface -o out/A.swiftmodule -I out
+
+// REQUIRES: OS=macosx

test/Serialization/module_defining_interface.swift

@@ -18,8 +18,8 @@
 // RUN: llvm-bcanalyzer -dump %t/inputs/Foo.swiftmodule > %t/Foo.sdk.moduledump.txt
 // RUN: cat %t/Foo.sdk.moduledump.txt | %FileCheck %s -check-prefix CHECK-SDK-FOO
 
-// CHECK-FREESTANDING-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}}/> blob data = '{{.*}}{{/|\\}}modules{{/|\\}}Foo.swiftinterface'
-// CHECK-SDK-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}}/> blob data = 'usr/lib/Foo.swiftmodule/Foo.swiftinterface'
+// CHECK-FREESTANDING-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}} op0=0/> blob data = '{{.*}}{{/|\\}}modules{{/|\\}}Foo.swiftinterface'
+// CHECK-SDK-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}} op0=1/> blob data = 'usr/lib/Foo.swiftmodule/Foo.swiftinterface'
 
 //--- modules/Foo.swiftinterface
 // swift-interface-format-version: 1.0