Reland "[clangd] Add feature modules registry"

clang-tools-extra/clangd/FeatureModule.cpp

@@ -22,6 +22,10 @@ FeatureModule::Facilities &FeatureModule::facilities() {
   return *Fac;
 }
 
+void FeatureModuleSet::add(std::unique_ptr<FeatureModule> M) {
+  Modules.push_back(std::move(M));
+}
+
 bool FeatureModuleSet::addImpl(void *Key, std::unique_ptr<FeatureModule> M,
                                const char *Source) {
   if (!Map.try_emplace(Key, M.get()).second) {
@@ -33,5 +37,16 @@ bool FeatureModuleSet::addImpl(void *Key, std::unique_ptr<FeatureModule> M,
   return true;
 }
 
+FeatureModuleSet FeatureModuleSet::fromRegistry() {
+  FeatureModuleSet ModuleSet;
+  for (FeatureModuleRegistry::entry E : FeatureModuleRegistry::entries()) {
+    vlog("Adding feature module '{0}' ({1})", E.getName(), E.getDesc());
+    ModuleSet.add(E.instantiate());
+  }
+  return ModuleSet;
+}
+
 } // namespace clangd
 } // namespace clang
+
+LLVM_INSTANTIATE_REGISTRY(clang::clangd::FeatureModuleRegistry)

clang-tools-extra/clangd/FeatureModule.h

@@ -15,6 +15,7 @@
 #include "llvm/ADT/FunctionExtras.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/JSON.h"
+#include "llvm/Support/Registry.h"
 #include <memory>
 #include <optional>
 #include <type_traits>
@@ -143,9 +144,14 @@ class FeatureModule {
 
 /// A FeatureModuleSet is a collection of feature modules installed in clangd.
 ///
-/// Modules can be looked up by type, or used via the FeatureModule interface.
-/// This allows individual modules to expose a public API.
-/// For this reason, there can be only one feature module of each type.
+/// Modules added with explicit type specification can be looked up by type, or
+/// used via the FeatureModule interface. This allows individual modules to
+/// expose a public API. For this reason, there can be only one feature module
+/// of each type.
+///
+/// Modules added using a base class pointer can be used only via the
+/// FeatureModule interface and can't be looked up by type, thus custom public
+/// API (if provided by the module) can't be used.
 ///
 /// The set owns the modules. It is itself owned by main, not ClangdServer.
 class FeatureModuleSet {
@@ -164,6 +170,8 @@ class FeatureModuleSet {
 public:
   FeatureModuleSet() = default;
 
+  static FeatureModuleSet fromRegistry();
+
   using iterator = llvm::pointee_iterator<decltype(Modules)::iterator>;
   using const_iterator =
       llvm::pointee_iterator<decltype(Modules)::const_iterator>;
@@ -172,6 +180,7 @@ class FeatureModuleSet {
   const_iterator begin() const { return const_iterator(Modules.begin()); }
   const_iterator end() const { return const_iterator(Modules.end()); }
 
+  void add(std::unique_ptr<FeatureModule> M);
   template <typename Mod> bool add(std::unique_ptr<Mod> M) {
     return addImpl(&ID<Mod>::Key, std::move(M), LLVM_PRETTY_FUNCTION);
   }
@@ -185,6 +194,8 @@ class FeatureModuleSet {
 
 template <typename Mod> int FeatureModuleSet::ID<Mod>::Key;
 
+using FeatureModuleRegistry = llvm::Registry<FeatureModule>;
+
 } // namespace clangd
 } // namespace clang
 #endif

clang-tools-extra/clangd/tool/ClangdMain.cpp

@@ -13,6 +13,7 @@
 #include "Config.h"
 #include "ConfigProvider.h"
 #include "Feature.h"
+#include "FeatureModule.h"
 #include "IncludeCleaner.h"
 #include "PathMapping.h"
 #include "Protocol.h"
@@ -1017,6 +1018,10 @@ clangd accepts flags on the commandline, and in the CLANGD_FLAGS environment var
                : static_cast<int>(ErrorResultCode::CheckFailed);
   }
 
+  FeatureModuleSet ModuleSet = FeatureModuleSet::fromRegistry();
+  if (ModuleSet.begin() != ModuleSet.end())
+    Opts.FeatureModules = &ModuleSet;
+
   // Initialize and run ClangdLSPServer.
   // Change stdin to binary to not lose \r\n on windows.
   llvm::sys::ChangeStdinToBinary();