[clang-tools-extra] [clangd] gitignore index directories (PR #90305)

[Sumit Sahrawat via cfe-commits]

https://github.com/sumit-sahrawat updated https://github.com/llvm/llvm-project/pull/90305

>From d4c734b59e6c3184d42af2b26ef50d57db662796 Mon Sep 17 00:00:00 2001
From: Sumit Sahrawat <139506625+sumit-sahrawat at users.noreply.github.com>
Date: Sat, 27 Apr 2024 06:57:29 +0530
Subject: [PATCH] [clangd] gitignore index directories

---
 .../clangd/index/BackgroundIndexStorage.cpp   | 26 +++++++++++++++++++
 .../clangd/test/background-index.test         | 12 +++++++++
 2 files changed, 38 insertions(+)

diff --git a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
index d887b09482a959..a4c2a4bf072fd4 100644
--- a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
+++ b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
@@ -33,6 +33,22 @@ std::string getShardPathFromFilePath(llvm::StringRef ShardRoot,
   return std::string(ShardRootSS);
 }
 
+std::string getGitignorePathForShardRoot(llvm::StringRef ShardRoot) {
+  llvm::SmallString<128> ShardRootSS(ShardRoot);
+  llvm::sys::path::append(ShardRootSS, ".gitignore");
+  return ShardRootSS.str().str();
+}
+
+llvm::Error addGitignore(llvm::StringRef Directory) {
+  auto FilePath = getGitignorePathForShardRoot(Directory);
+  return llvm::writeToOutput(FilePath, [](llvm::raw_ostream &OS) {
+    OS << "# This file is autogenerated by clangd.\n"
+       << "# If you change or delete it, it won't be recreated.\n"
+       << "*\n";
+    return llvm::Error::success();
+  });
+}
+
 // Uses disk as a storage for index shards.
 class DiskBackedIndexStorage : public BackgroundIndexStorage {
   std::string DiskShardRoot;
@@ -40,12 +56,22 @@ class DiskBackedIndexStorage : public BackgroundIndexStorage {
 public:
   // Creates `DiskShardRoot` and any parents during construction.
   DiskBackedIndexStorage(llvm::StringRef Directory) : DiskShardRoot(Directory) {
+    bool CreatingNewDirectory = !llvm::sys::fs::is_directory(DiskShardRoot);
+
     std::error_code OK;
     std::error_code EC = llvm::sys::fs::create_directories(DiskShardRoot);
     if (EC != OK) {
       elog("Failed to create directory {0} for index storage: {1}",
            DiskShardRoot, EC.message());
     }
+
+    if (CreatingNewDirectory) {
+      llvm::Error error = addGitignore(DiskShardRoot);
+      if (error) {
+        elog("Failed to add .gitignore to directory {0} for index storage: {1}",
+             DiskShardRoot, std::move(error));
+      }
+    }
   }
 
   std::unique_ptr<IndexFileIn>
diff --git a/clang-tools-extra/clangd/test/background-index.test b/clang-tools-extra/clangd/test/background-index.test
index 1983f0957dccf1..c937443a79b77e 100644
--- a/clang-tools-extra/clangd/test/background-index.test
+++ b/clang-tools-extra/clangd/test/background-index.test
@@ -18,6 +18,18 @@
 # RUN: ls %/t/.cache/clangd/index/foo.cpp.*.idx
 # RUN: ls %/t/sub_dir/.cache/clangd/index/foo.h.*.idx
 
+# Test that the index directories also have a .gitignore file present.
+# RUN: ls %/t/.cache/clangd/index/.gitignore
+# RUN: ls %/t/sub_dir/.cache/clangd/index/.gitignore
+
+# Delete .gitignore files to test that they're not recreated when loading an existing index directory.
+# RUN: rm %/t/.cache/clangd/index/.gitignore
+# RUN: rm %/t/sub_dir/.cache/clangd/index/.gitignore
+
 # Test the index is read from disk: delete code and restart clangd.
 # RUN: rm %/t/foo.cpp
 # RUN: clangd -background-index -lit-test < %/t/definition.jsonrpc | FileCheck %/t/definition.jsonrpc --check-prefixes=CHECK,USE
+
+# Test that the existing index directories do not have recreated .gitignore files.
+# RUN: test ! -e %/t/.cache/clangd/index/.gitignore
+# RUN: test ! -e %/t/sub_dir/.cache/clangd/index/.gitignore