Expose a ImportPrivateDependencies LangOpt for LLDB (NFC).

This patch allows controlling the automatic import of private dependencies
separately from the DebuggerSupport option, which currently also triggers this
behavior. With explicit modules + precise compiler invocations LLDB is moving
towards no longer needing this behavior.

rdar://133088201

Author: adrian-prantl

include/swift/Basic/LangOptions.h

@@ -267,6 +267,9 @@ namespace swift {
     /// Enable features useful for running in the debugger.
     bool DebuggerSupport = false;
 
+    /// When set, the module loader will try to import private dependencies.
+    bool ImportPrivateDependencies = false;
+
     /// Enable the MemoryBufferSerializedModuleImporter.
     /// Only used by lldb-moduleimport-test.
     bool EnableMemoryBufferImporter = false;

lib/Serialization/ModuleFile.cpp

@@ -308,11 +308,9 @@ ModuleFile::getTransitiveLoadingBehavior(const Dependency &dependency,
   // as a partial module.
   auto isPartialModule = mod->isMainModule();
 
-  return Core->getTransitiveLoadingBehavior(dependency.Core,
-                                            ctx.LangOpts.DebuggerSupport,
-                                            isPartialModule,
-                                            ctx.LangOpts.PackageName,
-                                            forTestable);
+  return Core->getTransitiveLoadingBehavior(
+      dependency.Core, ctx.LangOpts.ImportPrivateDependencies, isPartialModule,
+      ctx.LangOpts.PackageName, forTestable);
 }
 
 bool ModuleFile::mayHaveDiagnosticsPointingAtBuffer() const {

lib/Serialization/ModuleFileSharedCore.cpp

@@ -1789,7 +1789,7 @@ std::string ModuleFileSharedCore::resolveModuleDefiningFilePath(const StringRef
 ModuleLoadingBehavior
 ModuleFileSharedCore::getTransitiveLoadingBehavior(
                                           const Dependency &dependency,
-                                          bool debuggerMode,
+                                          bool importPrivateDependencies,
                                           bool isPartialModule,
                                           StringRef packageName,
                                           bool forTestable) const {
@@ -1805,7 +1805,7 @@ ModuleFileSharedCore::getTransitiveLoadingBehavior(
   if (dependency.isImplementationOnly()) {
     // Implementation-only dependencies are not usually loaded from
     // transitive imports.
-    if (debuggerMode || forTestable) {
+    if (importPrivateDependencies || forTestable) {
       // In the debugger, try to load the module if possible.
       // Same in the case of a testable import, try to load the dependency
       // but don't fail if it's missing as this could be source breaking.
@@ -1823,7 +1823,7 @@ ModuleFileSharedCore::getTransitiveLoadingBehavior(
     // on testable imports.
     if (forTestable || !moduleIsResilient) {
       return ModuleLoadingBehavior::Required;
-    } else if (debuggerMode) {
+    } else if (importPrivateDependencies) {
       return ModuleLoadingBehavior::Optional;
     } else {
       return ModuleLoadingBehavior::Ignored;
@@ -1837,7 +1837,7 @@ ModuleFileSharedCore::getTransitiveLoadingBehavior(
         forTestable ||
         !moduleIsResilient) {
       return ModuleLoadingBehavior::Required;
-    } else if (debuggerMode) {
+    } else if (importPrivateDependencies) {
       return ModuleLoadingBehavior::Optional;
     } else {
       return ModuleLoadingBehavior::Ignored;

lib/Serialization/ModuleFileSharedCore.h

@@ -624,8 +624,8 @@ class ModuleFileSharedCore {
 
   /// How should \p dependency be loaded for a transitive import via \c this?
   ///
-  /// If \p debuggerMode, more transitive dependencies should try to be loaded
-  /// as they can be useful in debugging.
+  /// If \p importPrivateDependencies, more transitive dependencies
+  /// should try to be loaded as they can be useful in debugging.
   ///
   /// If \p isPartialModule, transitive dependencies should be loaded as we're
   /// in merge-module mode.
@@ -639,7 +639,7 @@ class ModuleFileSharedCore {
   /// those non-public dependencies.
   ModuleLoadingBehavior
   getTransitiveLoadingBehavior(const Dependency &dependency,
-                               bool debuggerMode,
+                               bool importPrivateDependencies,
                                bool isPartialModule,
                                StringRef packageName,
                                bool forTestable) const;

lib/Serialization/SerializedModuleLoader.cpp

@@ -411,7 +411,7 @@ SerializedModuleLoaderBase::getImportsOfModule(
     ModuleLoadingBehavior dependencyTransitiveBehavior =
         loadedModuleFile.getTransitiveLoadingBehavior(
             dependency,
-            /*debuggerMode*/ false,
+            /*importPrivateDependencies*/ false,
             /*isPartialModule*/ false, packageName, isTestableImport);
     if (dependencyTransitiveBehavior > transitiveBehavior)
       continue;