Fix delta update.

Previous file was being loaded after the current file is written to disk.

src/cache.cc

@@ -4,6 +4,8 @@
 #include "platform.h"
 #include "language_server_api.h"
 
+#include <loguru/loguru.hpp>
+
 #include <algorithm>
 
 namespace {
@@ -30,7 +32,9 @@ std::unique_ptr<IndexFile> LoadCachedIndex(Config* config,
   if (!file_content)
     return nullptr;
 
-  return Deserialize(filename, *file_content, IndexFile::kCurrentVersion);
+  auto result = Deserialize(filename, *file_content, IndexFile::kCurrentVersion);
+  result->is_loaded_from_cache_ = true;
+  return result;
 }
 
 optional<std::string> LoadCachedFileContents(Config* config,
@@ -42,25 +46,21 @@ optional<std::string> LoadCachedFileContents(Config* config,
 }
 
 void WriteToCache(Config* config,
-                  const std::string& filename,
+                  IndexFile& file) {
-                  IndexFile& file,
-                  const optional<std::string>& indexed_file_content) {
   if (!config->enableCacheWrite)
     return;
 
   std::string cache_basename =
-      GetCachedBaseFileName(config->cacheDirectory, filename);
+      GetCachedBaseFileName(config->cacheDirectory, file.path);
 
-  if (indexed_file_content) {
+  LOG_IF_S(ERROR, file.file_contents_.empty()) << "Writing " << file.path << " to cache but it has no contents";
-    std::ofstream cache_content;
+
-    cache_content.open(cache_basename);
+  assert(!file.file_contents_.empty());
-    assert(cache_content.good());
+  std::ofstream cache_content;
-    cache_content << *indexed_file_content;
+  cache_content.open(cache_basename);
-    cache_content.close();
+  assert(cache_content.good());
-  }
+  cache_content << file.file_contents_;
-  else {
+  cache_content.close();
-    CopyFileTo(cache_basename, filename);
-  }
 
   std::string indexed_content = Serialize(file);
   std::ofstream cache;

src/cache.h

@@ -17,6 +17,4 @@ optional<std::string> LoadCachedFileContents(Config* config,
                                              const std::string& filename);
 
 void WriteToCache(Config* config,
-                  const std::string& filename,
+                  IndexFile& file);
-                  IndexFile& file,
-                  const optional<std::string>& indexed_file_contents);

src/command_line.cc

@@ -583,6 +583,7 @@ struct Index_OnIdMapped {
 
   std::unique_ptr<File> previous;
   std::unique_ptr<File> current;
+
   PerformanceImportFile perf;
   bool is_interactive;
 
@@ -638,8 +639,6 @@ struct Index_OnIndexed {
 
 
 
-
-
 
 
 
@@ -896,11 +895,6 @@ std::vector<Index_DoIdMap> DoParseFile(
     // Note: we are reusing the parent perf.
     perf.index_load_cached = time.ElapsedMicrosecondsAndReset();
 
-    // Write new cache to disk. Add file to list of paths that need to be reimported.
-    time.Reset();
-    WriteToCache(config, new_index->path, *new_index, new_index->file_contents_);
-    perf.index_save_to_disk = time.ElapsedMicrosecondsAndReset();
-
     // TODO/FIXME: real is_interactive
     bool is_interactive = false;
     LOG_S(INFO) << "Emitting index result for " << new_index->path;
@@ -952,6 +946,7 @@ bool IndexMain_DoParse(
 }
 
 bool IndexMain_DoCreateIndexUpdate(
+    Config* config,
     QueueManager* queue) {
   // TODO: Index_OnIdMapped dtor is failing because it seems that its contents have already been destroyed.
   optional<Index_OnIdMapped> response = queue->on_id_mapped.TryDequeue();
@@ -968,11 +963,19 @@ bool IndexMain_DoCreateIndexUpdate(
     previous_index = response->previous->file.get();
   }
 
+  // Build delta update.
   IndexUpdate update = IndexUpdate::CreateDelta(
       previous_id_map, response->current->ids.get(),
       previous_index, response->current->file.get());
   response->perf.index_make_delta = time.ElapsedMicrosecondsAndReset();
 
+  // Write new cache to disk if it is a fresh index.
+  if (!response->current->file->is_loaded_from_cache_) {
+    time.Reset();
+    WriteToCache(config, *response->current->file);
+    response->perf.index_save_to_disk = time.ElapsedMicrosecondsAndReset();
+  }
+
 #if false
 #define PRINT_SECTION(name) \
   if (response->perf.name) {\
@@ -1061,8 +1064,8 @@ void IndexMain(Config* config,
     bool did_parse = IndexMain_DoParse(config, queue, file_consumer_shared, &index);
 
     bool did_create_update =
-        IndexMain_DoCreateIndexUpdate(queue);
+        IndexMain_DoCreateIndexUpdate(config, queue);
-    
+
     bool did_load_previous = IndexMain_LoadPreviousIndex(config, queue);
 
     // Nothing to index and no index updates to create, so join some already

src/indexer.cc

@@ -356,10 +356,6 @@ std::string IndexFile::ToString() {
   return Serialize(*this);
 }
 
-void IndexFile::ClearLargeState() {
-  file_contents_ = "";
-}
-
 IndexType::IndexType(IndexTypeId id, const std::string& usr)
     : def(usr), id(id) {
   assert(usr.size() > 0);

src/indexer.h

@@ -480,6 +480,8 @@ struct IndexFile {
   std::vector<IndexFunc> funcs;
   std::vector<IndexVar> vars;
 
+  // True if this file was loaded from cache. Not serialized.
+  bool is_loaded_from_cache_ = false;
   // Diagnostics found when indexing this file. Not serialized.
   NonElidedVector<lsDiagnostic> diagnostics_;
   // File contents at the time of index. Not serialized.
@@ -498,7 +500,6 @@ struct IndexFile {
   IndexVar* Resolve(IndexVarId id);
 
   std::string ToString();
-  void ClearLargeState();
 };
 
 struct FileContents {