Modernize Module::RemapFile to return an Optional

[aprantl]

Summary

This addresses feedback raised in https://reviews.llvm.org/D104404.

[aprantl]

Ping.

[shafik]

LGTM

lldb/include/lldb/Core/Module.h

public:
   ///
   /// Remaps \a path if any source remappings match. This function does NOT
   /// stat the file system so it can be used in tight loops where debug info
   /// is being parsed.
   ///
   /// \param[in] path
   ///     The original source file path to try and remap.
   ///
-  /// \param[out] new_path
-  ///     The newly remapped filespec that is may or may not exist.
-  ///
   /// \return
-  ///     /b true if \a path was successfully located and \a new_path
-  ///     is filled in with a new source path, \b false otherwise.
-  bool RemapSourceFile(llvm::StringRef path, std::string &new_path) const;
+  ///     The newly remapped filespec that is may or may not exist if
+  ///     \a path was successfully located.
+  llvm::Optional<std::string> RemapSourceFile(llvm::StringRef path) const;
   bool RemapSourceFile(const char *, std::string &) const = delete;
 
   /// Update the ArchSpec to a more specific variant.
   bool MergeArchitecture(const ArchSpec &arch_spec);
 
   /// \class LookupInfo Module.h "lldb/Core/Module.h"
   /// A class that encapsulates name lookup information.
   ///

lldb/source/Core/Module.cpp

bool Module::FindSourceFile(const FileSpec &orig_spec,
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   if (auto remapped = m_source_mappings.FindFile(orig_spec)) {
     new_spec = *remapped;
     return true;
   }
   return false;
 }
 
-bool Module::RemapSourceFile(llvm::StringRef path,
-                             std::string &new_path) const {
+llvm::Optional<std::string> Module::RemapSourceFile(llvm::StringRef path) const {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
-  if (auto remapped = m_source_mappings.RemapPath(path)) {
-    new_path = remapped->GetPath();
-    return true;
-  }
-  return false;
+  if (auto remapped = m_source_mappings.RemapPath(path))
+    return remapped->GetPath();
+  return {};
 }
 
 void Module::RegisterXcodeSDK(llvm::StringRef sdk_name, llvm::StringRef sysroot) {
   XcodeSDK sdk(sdk_name.str());
   ConstString sdk_path(HostInfo::GetXcodeSDKPath(sdk));
   if (!sdk_path)
     return;
   // If the SDK changed for a previously registered source path, update it.

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

if (prologue.getVersion() <= 4) {
     // tables.
     support_files.Append(FileSpec());
     first_file = 1;
   }
 
   const size_t number_of_files = prologue.FileNames.size();
   for (size_t idx = first_file; idx <= number_of_files; ++idx) {
     std::string remapped_file;
-    if (auto file_path = GetFileByIndex(prologue, idx, compile_dir, style))
-      if (!module->RemapSourceFile(llvm::StringRef(*file_path), remapped_file))
+    if (auto file_path = GetFileByIndex(prologue, idx, compile_dir, style)) {
+      if (auto remapped = module->RemapSourceFile(llvm::StringRef(*file_path)))
+        remapped_file = *remapped;
+      else
         remapped_file = std::move(*file_path);
+    }
 
     // Unconditionally add an entry, so the indices match up.
     support_files.EmplaceBack(remapped_file, style);
   }
 
   return support_files;
 }
 
static void MakeAbsoluteAndRemap(FileSpec &file_spec, DWARFUnit &dwarf_cu,
                                  const ModuleSP &module_sp) {
   if (!file_spec)
     return;
   // If we have a full path to the compile unit, we don't need to
   // resolve the file.  This can be expensive e.g. when the source
   // files are NFS mounted.
   file_spec.MakeAbsolute(dwarf_cu.GetCompilationDirectory());
 
-  std::string remapped_file;
-  if (module_sp->RemapSourceFile(file_spec.GetPath(), remapped_file))
-    file_spec.SetFile(remapped_file, FileSpec::Style::native);
+  if (auto remapped_file = module_sp->RemapSourceFile(file_spec.GetPath()))
+    file_spec.SetFile(*remapped_file, FileSpec::Style::native);
 }
 
 lldb::CompUnitSP SymbolFileDWARF::ParseCompileUnit(DWARFCompileUnit &dwarf_cu) {
   CompUnitSP cu_sp;
   CompileUnit *comp_unit = (CompileUnit *)dwarf_cu.GetUserData();
   if (comp_unit) {
     // We already parsed this compile unit, had out a shared pointer to it
     cu_sp = comp_unit->shared_from_this();