[lldb] Add experimental setting for Swift explicit modules

lldb/include/lldb/Target/Target.h

@@ -188,6 +188,8 @@ class TargetProperties : public Properties {
 
   bool GetSwiftEnableFullDwarfDebugging() const;
 
+  bool GetSwiftAllowExplicitModules() const;
+
   Args GetSwiftPluginServerForPath() const;
 
   bool GetSwiftAutoImportFrameworks() const;

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -1578,9 +1578,10 @@ void SwiftASTContext::AddExtraClangArgs(const std::vector<std::string> &source,
     // module loading.
     // TODO: Incorporate loading explicit module dependencies to
     // speedup dependency resolution.
-    if (has_explicit_builds_enabled &&
-        match_explicit_build_option(clang_argument))
-      continue;
+    if (!Target::GetGlobalProperties().GetSwiftAllowExplicitModules())
+      if (has_explicit_builds_enabled &&
+          match_explicit_build_option(clang_argument))
+        continue;
 
     // Otherwise add the argument to the list.
     if (!IsMacroDefinition(clang_argument))

lldb/source/Target/Target.cpp

@@ -4987,6 +4987,19 @@ bool TargetProperties::GetSwiftEnableFullDwarfDebugging() const {
   return false;
 }
 
+bool TargetProperties::GetSwiftAllowExplicitModules() const {
+  const Property *exp_property =
+      m_collection_sp->GetPropertyAtIndex(ePropertyExperimental);
+  OptionValueProperties *exp_values =
+      exp_property->GetValue()->GetAsProperties();
+  if (exp_values)
+    return exp_values
+        ->GetPropertyAtIndexAs<bool>(ePropertySwiftAllowExplicitModules)
+        .value_or(false);
+
+  return false;
+}
+
 Args TargetProperties::GetSwiftPluginServerForPath() const {
   const uint32_t idx = ePropertySwiftPluginServerForPath;
 

lldb/source/Target/TargetProperties.td

@@ -28,8 +28,11 @@ let Definition = "target_experimental" in {
     ElementType<"String">,
     Desc<"A dictionary of plugin paths as keys and swift-plugin-server binaries as values">;
   def SwiftEnableFullDwarfDebugging: Property<"swift-enable-full-dwarf-debugging", "Boolean">,
-  DefaultFalse,
-  Desc<"Read full debug information from DWARF for Swift debugging, whenever possible">;
+    DefaultFalse,
+    Desc<"Read full debug information from DWARF for Swift debugging, whenever possible">;
+  def SwiftAllowExplicitModules: Property<"swift-allow-explicit-modules", "Boolean">,
+    DefaultFalse,
+    Desc<"Allows explicit module flags to be passed through to ClangImporter.">;
 }
 
 let Definition = "target" in {