[clangd] Auto-index watches global CDB for changes.

Summary:
Instead of receiving compilation commands, auto-index is triggered by just
filenames to reindex, and gets commands from the global comp DB internally.
This has advantages:
 - more of the work can be done asynchronously (fetching compilation commands
   upfront can be slow for large CDBs)
 - we get access to the CDB which can be used to retrieve interpolated commands
   for headers (useful in some cases where the original TU goes away)
 - fits nicely with the filename-only change observation from r347297

The interface to GlobalCompilationDatabase gets extended: when retrieving a
compile command, the GCDB can optionally report the project the file belongs to.
This naturally fits together with getCompileCommand: it's hard to implement one
without the other. But because most callers don't care, I've ended up with an
awkward optional-out-param-in-virtual method pattern - maybe there's a better
one.

This is the main missing integration point between ClangdServer and
BackgroundIndex, after this we should be able to add an auto-index flag.

Reviewers: ioeric, kadircet

Subscribers: MaskRay, jkorous, arphaman, cfe-commits, ilya-biryukov

Differential Revision: https://reviews.llvm.org/D54865

llvm-svn: 347538

1 files changed, 4 insertions, 1 deletions

diff --git a/clang-tools-extra/unittests/clangd/TestFS.cpp b/clang-tools-extra/unittests/clangd/TestFS.cpp
index 86e10725eaa..b0938a59840 100644
--- a/clang-tools-extra/unittests/clangd/TestFS.cpp
+++ b/clang-tools-extra/unittests/clangd/TestFS.cpp
@@ -39,7 +39,8 @@ MockCompilationDatabase::MockCompilationDatabase(StringRef Directory,
 }
 
 Optional<tooling::CompileCommand>
-MockCompilationDatabase::getCompileCommand(PathRef File) const {
+MockCompilationDatabase::getCompileCommand(PathRef File,
+                                           ProjectInfo *Project) const {
   if (ExtraClangFlags.empty())
     return None;
 
@@ -58,6 +59,8 @@ MockCompilationDatabase::getCompileCommand(PathRef File) const {
     CommandLine.push_back(RelativeFilePath.str());
   }
 
+  if (Project)
+    Project->SourceRoot = Directory;
   return {tooling::CompileCommand(
       Directory != StringRef() ? Directory : sys::path::parent_path(File),
       FileName, std::move(CommandLine), "")};