[clangd] Clangd running with --experimental-modules-support crashes when the compilation database is unavailable

[slavek-kucera]

fixes #132413

[github-actions]

Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write permissions for the repository. In which case you can instead tag reviewers by name in a comment by using @ followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the LLVM GitHub User Guide.

You can also ask questions in a comment on this PR, on the LLVM Discord or on the forums.

[llvmbot]

@llvm/pr-subscribers-clangd

@llvm/pr-subscribers-clang-tools-extra

Author: None (slavek-kucera)

Changes

fixes llvm/llvm-project#132413

---

Full diff: https://github.com/llvm/llvm-project/pull/153802.diff

1 Files Affected:

• (modified) clang-tools-extra/clangd/GlobalCompilationDatabase.cpp (+2)

diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
index 7c0eb9651feaa..8c993db2d6d02 100644
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
@@ -833,6 +833,8 @@ bool OverlayCDB::setCompileCommand(PathRef File,
 std::unique_ptr<ProjectModules>
 OverlayCDB::getProjectModules(PathRef File) const {
   auto MDB = DelegatingCDB::getProjectModules(File);
+  if (!MDB)
+    return {};
   MDB->setCommandMangler([&Mangler = Mangler](tooling::CompileCommand &Command,
                                               PathRef CommandPath) {
     Mangler(Command, CommandPath);

[ChuanqiXu9]

It will be better to have a test either in unittest like clang-tools-extra/clangd/unittests/PrerequisiteModulesTest.cpp or lit test like clang-tools-extra/clangd/test/modules.test

[ChuanqiXu9]

Suggested change

	if (!MDB)
	return {};
	if (!MDB) {
	log("Failed to get compilation Database for {0}", File);
	return {};
	}

[github-actions]

@slavek-kucera Congratulations on having your first Pull Request (PR) merged into the LLVM Project!

Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR.

Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues.

How to do this, and the rest of the post-merge process, is covered in detail here.

If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again.

If you don't get any reports, no action is required from you. Your changes are working as expected, well done!