Merge pull request #63310 from artemcm/ScanDepsNoImplOnlyDeps

[Dependency Scanning] Do not process transitive `@_implementationOnly` dependencies of binary Swift modules

Author: artemcm

lib/Serialization/SerializedModuleLoader.cpp

@@ -420,6 +420,12 @@ llvm::ErrorOr<ModuleDependencyInfo> SerializedModuleLoaderBase::scanModuleFile(
     if (dependency.isHeader())
       continue;
 
+    // Transitive @_implementationOnly dependencies of
+    // binary modules are not required to be imported during normal builds
+    // TODO: This is worth revisiting for debugger purposes
+    if (dependency.isImplementationOnly())
+      continue;
+
     // Find the top-level module name.
     auto modulePathStr = dependency.getPrettyPrintedPath();
     StringRef moduleName = modulePathStr;

test/ScanDependencies/no_trasitive_implementation-only_deps.swift

@@ -0,0 +1,18 @@
+// RUN: %empty-directory(%t)
+// RUN: mkdir -p %t/clang-module-cache
+// RUN: mkdir -p %t/Frameworks
+// RUN: mkdir -p %t/Frameworks/Foo.framework/
+// RUN: mkdir -p %t/Frameworks/Foo.framework/Modules
+// RUN: mkdir -p %t/Frameworks/Foo.framework/Modules/Foo.swiftmodule
+
+// Build a dependency into a binary module with an @_implementationOnly dependency on `E`
+// RUN: echo "@_implementationOnly import E;public func foo() {}" >> %t/foo.swift
+// RUN: %target-swift-frontend -emit-module -emit-module-path %t/Frameworks/Foo.framework/Modules/Foo.swiftmodule/%target-cpu.swiftmodule -module-cache-path %t.module-cache %t/foo.swift -module-name Foo -I %S/Inputs/Swift
+
+// Run the scan
+// RUN: %target-swift-frontend -scan-dependencies %s -o %t/deps.json -F %t/Frameworks/ -sdk %t
+// RUN: %FileCheck %s < %t/deps.json
+
+import Foo
+
+// CHECK-NOT: "swift": "E"