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

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clangd

Author: Sumit Sahrawat (sumit-sahrawat)

<details>
<summary>Changes</summary>

This PR makes `clangd` add a `.gitignore` file when creating index directories (`.cache/clangd/index`), with the content `*`. This makes git repos automatically ignore this directory.

This is similar to the behaviour of tools like meson, which adds a gitignore file to the build directories.

---
Full diff: https://github.com/llvm/llvm-project/pull/90305.diff


2 Files Affected:

- (modified) clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp (+24) 
- (modified) clang-tools-extra/clangd/test/background-index.test (+12) 


``````````diff
diff --git a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
index d887b09482a959..2931d5999ee5cd 100644
--- a/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
+++ b/clang-tools-extra/clangd/index/BackgroundIndexStorage.cpp
@@ -33,6 +33,20 @@ 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::writeFileAtomically(
+      FilePath + ".tmp.%%%%%%%%", FilePath,
+      "# This file is autogenerated by clangd. If you change or delete it, "
+      "it won't be recreated.\n*");
+}
+
 // Uses disk as a storage for index shards.
 class DiskBackedIndexStorage : public BackgroundIndexStorage {
   std::string DiskShardRoot;
@@ -40,12 +54,22 @@ 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

``````````

</details>


https://github.com/llvm/llvm-project/pull/90305