[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, 5 insertions, 2 deletions

diff --git a/clang-tools-extra/unittests/clangd/GlobalCompilationDatabaseTests.cpp b/clang-tools-extra/unittests/clangd/GlobalCompilationDatabaseTests.cpp
index f502f79b71f..f3916108c63 100644
--- a/clang-tools-extra/unittests/clangd/GlobalCompilationDatabaseTests.cpp
+++ b/clang-tools-extra/unittests/clangd/GlobalCompilationDatabaseTests.cpp
@@ -41,9 +41,12 @@ class OverlayCDBTest : public ::testing::Test {
   class BaseCDB : public GlobalCompilationDatabase {
   public:
     Optional<tooling::CompileCommand>
-    getCompileCommand(StringRef File) const override {
-      if (File == testPath("foo.cc"))
+    getCompileCommand(StringRef File, ProjectInfo *Project) const override {
+      if (File == testPath("foo.cc")) {
+        if (Project)
+          Project->SourceRoot = testRoot();
         return cmd(File, "-DA=1");
+      }
       return None;
     }