[ScanDependencies] Do not count optional dependencies when not needed

If a testable module is loaded from a non-testable import, ignore its
optional dependencies because the consumer should not use them. This
matches the behavior of the implicit build or the behavior how
forwarding module is created.

(cherry picked from commit 77fefe9)

Author: cachemeifyoucan

include/swift/Serialization/SerializedModuleLoader.h

@@ -174,7 +174,7 @@ class SerializedModuleLoaderBase : public ModuleLoader {
   static BinaryModuleImports
   getImportsOfModule(const ModuleFileSharedCore &loadedModule,
                      ModuleLoadingBehavior transitiveBehavior,
-                     StringRef packageName);
+                     StringRef packageName, bool isTestableImport);
 
   /// Load the module file into a buffer and also collect its module name.
   static std::unique_ptr<llvm::MemoryBuffer>

lib/Serialization/SerializedModuleLoader.cpp

@@ -395,7 +395,8 @@ std::error_code SerializedModuleLoaderBase::openModuleFile(
 SerializedModuleLoaderBase::BinaryModuleImports
 SerializedModuleLoaderBase::getImportsOfModule(
     const ModuleFileSharedCore &loadedModuleFile,
-    ModuleLoadingBehavior transitiveBehavior, StringRef packageName) {
+    ModuleLoadingBehavior transitiveBehavior, StringRef packageName,
+    bool isTestableImport) {
   llvm::StringSet<> importedModuleNames;
   std::string importedHeader = "";
   for (const auto &dependency : loadedModuleFile.getDependencies()) {
@@ -410,8 +411,7 @@ SerializedModuleLoaderBase::getImportsOfModule(
         loadedModuleFile.getTransitiveLoadingBehavior(
             dependency,
             /*debuggerMode*/ false,
-            /*isPartialModule*/ false, packageName,
-            loadedModuleFile.isTestable());
+            /*isPartialModule*/ false, packageName, isTestableImport);
     if (dependencyTransitiveBehavior > transitiveBehavior)
       continue;
 
@@ -454,13 +454,6 @@ SerializedModuleLoaderBase::scanModuleFile(Twine modulePath, bool isFramework,
                            modulePath.str());
       return std::make_error_code(std::errc::no_such_file_or_directory);
     }
-
-    if (loadedModuleFile->isTestable() && !isTestableImport) {
-      if (Ctx.LangOpts.EnableModuleLoadingRemarks)
-        Ctx.Diags.diagnose(SourceLoc(), diag::skip_module_testable,
-                           modulePath.str());
-      return std::make_error_code(std::errc::no_such_file_or_directory);
-    }
   }
 
   // Some transitive dependencies of binary modules are not required to be
@@ -471,12 +464,12 @@ SerializedModuleLoaderBase::scanModuleFile(Twine modulePath, bool isFramework,
   //       optional.
   auto binaryModuleImports =
       getImportsOfModule(*loadedModuleFile, ModuleLoadingBehavior::Required,
-                         Ctx.LangOpts.PackageName);
+                         Ctx.LangOpts.PackageName, isTestableImport);
 
   // Lookup optional imports of this module also
   auto binaryModuleOptionalImports =
       getImportsOfModule(*loadedModuleFile, ModuleLoadingBehavior::Optional,
-                         Ctx.LangOpts.PackageName);
+                         Ctx.LangOpts.PackageName, isTestableImport);
 
   auto importedModuleSet = binaryModuleImports.moduleImports;
   std::vector<std::string> importedModuleNames;

test/ScanDependencies/testable-dependencies.swift

@@ -16,13 +16,12 @@
 // RUN:   -emit-module-interface-path %t/regular/A.swiftinterface -enable-library-evolution -I %t/internal \
 // RUN:   %t/A.swift
 
-/// Import testable build, should use interface.
+/// Import testable build, should use binary but no extra dependencies.
 // RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-serialized -module-name Test %t/main.swift \
 // RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib \
-// RUN:   -o %t/deps1.json -I %t/testable -swift-version 5 -Rmodule-loading 2>&1 | %FileCheck %s --check-prefix DIAG
-// DIAG: remark: skip swiftmodule built with '-enable-testing'
+// RUN:   -o %t/deps1.json -I %t/testable -swift-version 5 -Rmodule-loading
 // RUN: %{python} %S/../CAS/Inputs/SwiftDepsExtractor.py %t/deps1.json Test directDependencies | %FileCheck %s --check-prefix TEST1
-// TEST1: "swift": "A"
+// TEST1:  "swiftPrebuiltExternal": "A"
 // RUN: %{python} %S/../CAS/Inputs/SwiftDepsExtractor.py %t/deps1.json A directDependencies | %FileCheck %s --check-prefix EMPTY --allow-empty
 // EMPTY-NOT: B
 
@@ -56,12 +55,15 @@
 // RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib -enable-testing \
 // RUN:   -o %t/deps5.json -I %t/regular -swift-version 5 -Rmodule-loading
 
-/// Regular import a testable module with no interface, this is a dependency scanning error.
+/// Regular import a testable module with no interface, don't load optional dependencies.
 // RUN: rm %t/testable/A.swiftinterface
 // RUN: %target-swift-frontend -scan-dependencies -module-load-mode prefer-interface -module-name Test %t/main.swift \
 // RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import -parse-stdlib -enable-testing \
-// RUN:   -o %t/deps6.json -I %t/testable -swift-version 5 -Rmodule-loading 2>&1 | %FileCheck %s --check-prefix ERROR
-// ERROR: error: Unable to find module dependency: 'A'
+// RUN:   -o %t/deps6.json -I %t/testable -swift-version 5 -Rmodule-loading
+// RUN: %{python} %S/../CAS/Inputs/SwiftDepsExtractor.py %t/deps6.json Test directDependencies | %FileCheck %s --check-prefix TEST6
+// TEST6:  "swiftPrebuiltExternal": "A"
+// RUN: %{python} %S/../CAS/Inputs/SwiftDepsExtractor.py %t/deps6.json swiftPrebuiltExternal:A directDependencies | %FileCheck %s --check-prefix EMPTY --allow-empty
+
 
 //--- main.swift
 import A