Add cache.{inMemoryAfterLoad,useHierarchy}

cache.useHierarchy: store cache files as $directory/a/b/c.cc.blob to
work around NAME_MAX limitation.

cache.inMemoryAfterLoad: during incremental updates, the removed file
index is taken from the in-memory copy. This avoids cache corruption if
the index file is changed after the initial load, which may happen when
several language clients open the same project and share the same cache
directory.

Also rename cacheDirectory cacheFormat to cache.{directory,format}

src/config.hh

@@ -40,19 +40,37 @@ struct Config {
   std::string compilationDatabaseCommand;
   // Directory containing compile_commands.json.
   std::string compilationDatabaseDirectory;
+
+  struct Cache {
     // Cache directory for indexed files, either absolute or relative to the
     // project root.
-  // If empty, cache will be stored in memory.
-  std::string cacheDirectory = ".ccls-cache";
+    //
+    // If empty, retainInMemory will be set to true and cache will be stored in
+    // memory.
+    std::string directory = ".ccls-cache";
+
     // Cache serialization format.
     //
-  // "json" generates `cacheDirectory/.../xxx.json` files which can be pretty
+    // "json" generates $directory/.../xxx.json files which can be pretty
     // printed with jq.
     //
     // "binary" uses a compact binary serialization format.
-  // It is not schema-aware and you need to re-index whenever an internal struct
-  // member has changed.
-  SerializeFormat cacheFormat = SerializeFormat::Binary;
+    // It is not schema-aware and you need to re-index whenever an internal
+    // struct member has changed.
+    SerializeFormat format = SerializeFormat::Binary;
+
+    // If true, keep a copy of file index in memory (which increases memory
+    // usage). During incremental updates, the removed file index will be taken
+    // from the in-memory copy, instead of the on-disk file.
+    bool retainInMemory = true;
+
+    // If false, store cache files as $directory/@a@b/c.cc.blob
+    //
+    // If true, $directory/a/b/c.cc.blob. If cache.directory is absolute, make
+    // sure different projects use different cache.directory as they would have
+    // conflicting cache files for system headers.
+    bool useHierarchy = false;
+  } cache;
 
   struct ServerCap {
     struct DocumentOnTypeFormattingOptions {
@@ -292,6 +310,8 @@ struct Config {
     int maxNum = 2000;
   } xref;
 };
+REFLECT_STRUCT(Config::Cache, directory, format, retainInMemory,
+               useHierarchy);
 REFLECT_STRUCT(Config::ServerCap::DocumentOnTypeFormattingOptions,
                firstTriggerCharacter, moreTriggerCharacter);
 REFLECT_STRUCT(Config::ServerCap::Workspace::WorkspaceFolders, supported,
@@ -321,9 +341,9 @@ REFLECT_STRUCT(Config::Session, maxNum);
 REFLECT_STRUCT(Config::WorkspaceSymbol, caseSensitivity, maxNum, sort);
 REFLECT_STRUCT(Config::Xref, maxNum);
 REFLECT_STRUCT(Config, compilationDatabaseCommand, compilationDatabaseDirectory,
-               cacheDirectory, cacheFormat, capabilities, clang, client,
-               codeLens, completion, diagnostics, highlight, index, request,
-               session, workspaceSymbol, xref);
+               cache, capabilities, clang, client, codeLens, completion,
+               diagnostics, highlight, index, request, session, workspaceSymbol,
+               xref);
 
 extern Config *g_config;
 

src/messages/initialize.cc

@@ -293,12 +293,12 @@ void Initialize(MessageHandler *m, InitializeParam &param, ReplyOnce &reply) {
     Reflect(json_writer, *g_config);
     LOG_S(INFO) << "initializationOptions: " << output.GetString();
 
-    if (g_config->cacheDirectory.size()) {
-      SmallString<256> Path(g_config->cacheDirectory);
+    if (g_config->cache.directory.size()) {
+      SmallString<256> Path(g_config->cache.directory);
       sys::fs::make_absolute(project_path, Path);
       // Use upper case for the Driver letter on Windows.
-      g_config->cacheDirectory = NormalizePath(Path.str());
-      EnsureEndsInSlash(g_config->cacheDirectory);
+      g_config->cache.directory = NormalizePath(Path.str());
+      EnsureEndsInSlash(g_config->cache.directory);
     }
   }
 
@@ -345,13 +345,16 @@ void Initialize(MessageHandler *m, InitializeParam &param, ReplyOnce &reply) {
   }
   if (param.workspaceFolders.empty())
     g_config->workspaceFolders.push_back(project_path);
-  if (g_config->cacheDirectory.size())
+
+  if (g_config->cache.directory.empty())
+    g_config->cache.retainInMemory = true;
+  else if (!g_config->cache.useHierarchy)
     for (const std::string &folder : g_config->workspaceFolders) {
       // Create two cache directories for files inside and outside of the
       // project.
       std::string escaped = EscapeFileName(folder.substr(0, folder.size() - 1));
-      sys::fs::create_directories(g_config->cacheDirectory + escaped);
-      sys::fs::create_directories(g_config->cacheDirectory + '@' + escaped);
+      sys::fs::create_directories(g_config->cache.directory + escaped);
+      sys::fs::create_directories(g_config->cache.directory + '@' + escaped);
     }
 
   idx::Init();

src/messages/workspace.cc

@@ -46,8 +46,8 @@ void MessageHandler::workspace_didChangeWatchedFiles(
     DidChangeWatchedFilesParam &param) {
   for (auto &event : param.changes) {
     std::string path = event.uri.GetPath();
-    if ((g_config->cacheDirectory.size() &&
-         StringRef(path).startswith(g_config->cacheDirectory)) ||
+    if ((g_config->cache.directory.size() &&
+         StringRef(path).startswith(g_config->cache.directory)) ||
         lookupExtension(path).first == LanguageId::Unknown)
       return;
     for (std::string cur = path; cur.size(); cur = sys::path::parent_path(cur))

src/pipeline.cc

@@ -137,7 +137,7 @@ bool CacheInvalid(VFS *vfs, IndexFile *prev, const std::string &path,
 };
 
 std::string AppendSerializationFormat(const std::string &base) {
-  switch (g_config->cacheFormat) {
+  switch (g_config->cache.format) {
   case SerializeFormat::Binary:
     return base + ".blob";
   case SerializeFormat::Json:
@@ -145,27 +145,36 @@ std::string AppendSerializationFormat(const std::string &base) {
   }
 }
 
-std::string GetCachePath(const std::string &source_file) {
-  for (auto &root : g_config->workspaceFolders)
-    if (StringRef(source_file).startswith(root)) {
-      auto len = root.size();
-      return g_config->cacheDirectory +
-             EscapeFileName(root.substr(0, len - 1)) + '/' +
-             EscapeFileName(source_file.substr(len));
+std::string GetCachePath(const std::string &src) {
+  if (g_config->cache.useHierarchy) {
+    std::string ret =
+        g_config->cache.directory + (src[0] == '/' ? src.substr(1) : src);
+#ifdef _WIN32
+    std::replace(src.begin(), src.end(), ':', '@');
+#endif
+    return ret;
   }
-  return g_config->cacheDirectory + '@' +
+  for (auto &root : g_config->workspaceFolders)
+    if (StringRef(src).startswith(root)) {
+      auto len = root.size();
+      return g_config->cache.directory +
+             EscapeFileName(root.substr(0, len - 1)) + '/' +
+             EscapeFileName(src.substr(len));
+    }
+  return g_config->cache.directory + '@' +
          EscapeFileName(g_config->fallbackFolder.substr(
              0, g_config->fallbackFolder.size() - 1)) +
-         '/' + EscapeFileName(source_file);
+         '/' + EscapeFileName(src);
 }
 
 std::unique_ptr<IndexFile> RawCacheLoad(const std::string &path) {
-  if (g_config->cacheDirectory.empty()) {
+  if (g_config->cache.retainInMemory) {
     std::shared_lock lock(g_index_mutex);
     auto it = g_index.find(path);
-    if (it == g_index.end())
-      return nullptr;
+    if (it != g_index.end())
       return std::make_unique<IndexFile>(it->second.index);
+    if (g_config->cache.directory.empty())
+      return nullptr;
   }
 
   std::string cache_path = GetCachePath(path);
@@ -175,7 +184,7 @@ std::unique_ptr<IndexFile> RawCacheLoad(const std::string &path) {
   if (!file_content || !serialized_indexed_content)
     return nullptr;
 
-  return ccls::Deserialize(g_config->cacheFormat, path,
+  return ccls::Deserialize(g_config->cache.format, path,
                            *serialized_indexed_content, *file_content,
                            IndexFile::kMajorVersion);
 }
@@ -371,20 +380,25 @@ bool Indexer_Parse(SemaManager *completion, WorkingFiles *wfiles,
         prev = RawCacheLoad(path);
       else
         prev.reset();
-      if (g_config->cacheDirectory.empty()) {
+      if (g_config->cache.retainInMemory) {
         std::lock_guard lock(g_index_mutex);
         auto it = g_index.insert_or_assign(
           path, InMemoryIndexFile{curr->file_contents, *curr});
         std::string().swap(it.first->second.index.file_contents);
-      } else {
+      }
+      if (g_config->cache.directory.size()) {
         std::string cache_path = GetCachePath(path);
         if (deleted) {
           (void)sys::fs::remove(cache_path);
           (void)sys::fs::remove(AppendSerializationFormat(cache_path));
         } else {
+          if (g_config->cache.useHierarchy)
+            sys::fs::create_directories(
+                sys::path::parent_path(cache_path, sys::path::Style::posix),
+                true);
           WriteToFile(cache_path, curr->file_contents);
           WriteToFile(AppendSerializationFormat(cache_path),
-                      Serialize(g_config->cacheFormat, *curr));
+                      Serialize(g_config->cache.format, *curr));
         }
       }
       on_indexed->PushBack(IndexUpdate::CreateDelta(prev.get(), curr.get()),
@@ -719,7 +733,7 @@ void Index(const std::string &path, const std::vector<const char *> &args,
 }
 
 std::optional<std::string> LoadIndexedContent(const std::string &path) {
-  if (g_config->cacheDirectory.empty()) {
+  if (g_config->cache.directory.empty()) {
     std::shared_lock lock(g_index_mutex);
     auto it = g_index.find(path);
     if (it == g_index.end())

src/utils.cc

@@ -124,9 +124,10 @@ void EnsureEndsInSlash(std::string &path) {
 
 std::string EscapeFileName(std::string path) {
   bool slash = path.size() && path.back() == '/';
-  for (char &c : path)
-    if (c == '\\' || c == '/' || c == ':')
-      c = '@';
+#ifdef _WIN32
+  std::replace(path.begin(), path.end(), ':', '@');
+#endif
+  std::replace(path.begin(), path.end(), '/', '@');
   if (slash)
     path += '/';
   return path;