[clang-tools-extra] [clangd] fix wrong resouce-dir (PR #203332)

[via cfe-commits]

https://github.com/playerC updated https://github.com/llvm/llvm-project/pull/203332

>From 43e24b2daf354ebb4c45af990d9b858b92031f46 Mon Sep 17 00:00:00 2001
From: player <playerc at msn.cn>
Date: Fri, 12 Jun 2026 00:22:01 +0800
Subject: [PATCH] [clangd] fix wrong resouce-dir

clangd and LLVM are installed separately. When clangd and
LLVM are installed under different install prefixes,
clangd constructs a fake resource-dir based on its own
installation directory and set it to the underlying Clang compilers.

This change modifies the logic to detect default resource-dir, and
add some logs.

detect resource-dir logic:
  `XX` is clang version clangd is depend on.

  if relative to clangd , `../lib/clang/XX` exsits, use it.
  if relative to default clang , `../lib/clang/XX` exsits, use it.

  or ResourceDir is null.

And when  default resource-dir is null , it will show an error
on create CommandMangler.
---
 clang-tools-extra/clangd/CompileCommands.cpp | 24 +++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/clang-tools-extra/clangd/CompileCommands.cpp b/clang-tools-extra/clangd/CompileCommands.cpp
index f8bc9a9ca81fd..e8005435e1836 100644
--- a/clang-tools-extra/clangd/CompileCommands.cpp
+++ b/clang-tools-extra/clangd/CompileCommands.cpp
@@ -135,6 +135,28 @@ std::string detectStandardResourceDir() {
   return GetResourcesPath("clangd", (void *)&StaticForMainAddr);
 }
 
+std::optional<std::string>
+detectResourceDirWithClangPath(std::optional<std::string> ClangPath) {
+  std::string ResourceDir = detectStandardResourceDir();
+  if (llvm::sys::fs::exists(ResourceDir))
+    return ResourceDir;
+  vlog("Auto-detected standard resource directory '{0}' doesn't exist",
+       ResourceDir);
+
+  if (ClangPath) {
+    ResourceDir = GetResourcesPath(*ClangPath);
+    if (llvm::sys::fs::exists(ResourceDir))
+      return ResourceDir;
+    vlog("Auto-detected using clang path '{0}' "
+         "resource directory '{1}' doesn't exist",
+         *ClangPath, ResourceDir);
+  }
+
+  elog("Failed to auto-detect resource directory, "
+       "specify it manually via --resource-dir command line argument");
+  return std::nullopt;
+}
+
 // The path passed to argv[0] is important:
 //  - its parent directory is Driver::Dir, used for library discovery
 //  - its basename affects CLI parsing (clang-cl) and other settings
@@ -188,7 +210,7 @@ static std::string resolveDriver(llvm::StringRef Driver, bool FollowSymlink,
 CommandMangler CommandMangler::detect() {
   CommandMangler Result;
   Result.ClangPath = detectClangPath();
-  Result.ResourceDir = detectStandardResourceDir();
+  Result.ResourceDir = detectResourceDirWithClangPath(Result.ClangPath);
   Result.Sysroot = detectSysroot();
   return Result;
 }