[clangd] [C++20] [Modules] Introduce initial support for C++20 Modules

clang-tools-extra/clangd/CMakeLists.txt

@@ -97,12 +97,14 @@ add_clang_library(clangDaemon
   IncludeFixer.cpp
   InlayHints.cpp
   JSONTransport.cpp
+  ModulesBuilder.cpp
   PathMapping.cpp
   Protocol.cpp
   Quality.cpp
   ParsedAST.cpp
   Preamble.cpp
   RIFF.cpp
+  ScanningProjectModules.cpp
   Selection.cpp
   SemanticHighlighting.cpp
   SemanticSelection.cpp
@@ -161,6 +163,7 @@ clang_target_link_libraries(clangDaemon
   clangAST
   clangASTMatchers
   clangBasic
+  clangDependencyScanning
   clangDriver
   clangFormat
   clangFrontend

clang-tools-extra/clangd/ClangdLSPServer.cpp

@@ -14,6 +14,7 @@
 #include "Feature.h"
 #include "GlobalCompilationDatabase.h"
 #include "LSPBinder.h"
+#include "ModulesBuilder.h"
 #include "Protocol.h"
 #include "SemanticHighlighting.h"
 #include "SourceCode.h"
@@ -51,6 +52,7 @@
 
 namespace clang {
 namespace clangd {
+
 namespace {
 // Tracks end-to-end latency of high level lsp calls. Measurements are in
 // seconds.
@@ -563,6 +565,12 @@ void ClangdLSPServer::onInitialize(const InitializeParams &Params,
     Mangler.ResourceDir = *Opts.ResourceDir;
   CDB.emplace(BaseCDB.get(), Params.initializationOptions.fallbackFlags,
               std::move(Mangler));
+
+  if (Opts.EnableExperimentalModulesSupport) {
+    ModulesManager.emplace(*CDB);
+    Opts.ModulesManager = &*ModulesManager;
+  }
+
   {
     // Switch caller's context with LSPServer's background context. Since we
     // rather want to propagate information from LSPServer's context into the

clang-tools-extra/clangd/ClangdLSPServer.h

@@ -63,6 +63,9 @@ class ClangdLSPServer : private ClangdServer::Callbacks,
 
     /// Limit the number of references returned (0 means no limit).
     size_t ReferencesLimit = 0;
+
+    /// Flag to hint the experimental modules support is enabled.
+    bool EnableExperimentalModulesSupport = false;
   };
 
   ClangdLSPServer(Transport &Transp, const ThreadsafeFS &TFS,
@@ -323,6 +326,8 @@ class ClangdLSPServer : private ClangdServer::Callbacks,
   std::optional<OverlayCDB> CDB;
   // The ClangdServer is created by the "initialize" LSP method.
   std::optional<ClangdServer> Server;
+  // Manages to build module files.
+  std::optional<ModulesBuilder> ModulesManager;
 };
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/ClangdServer.cpp

@@ -216,6 +216,7 @@ ClangdServer::ClangdServer(const GlobalCompilationDatabase &CDB,
                            Callbacks *Callbacks)
     : FeatureModules(Opts.FeatureModules), CDB(CDB), TFS(TFS),
       DynamicIdx(Opts.BuildDynamicSymbolIndex ? new FileIndex() : nullptr),
+      ModulesManager(Opts.ModulesManager),
       ClangTidyProvider(Opts.ClangTidyProvider),
       UseDirtyHeaders(Opts.UseDirtyHeaders),
       LineFoldingOnly(Opts.LineFoldingOnly),
@@ -308,6 +309,7 @@ void ClangdServer::addDocument(PathRef File, llvm::StringRef Contents,
   Inputs.Index = Index;
   Inputs.ClangTidyProvider = ClangTidyProvider;
   Inputs.FeatureModules = FeatureModules;
+  Inputs.ModulesManager = ModulesManager;
   bool NewFile = WorkScheduler->update(File, Inputs, WantDiags);
   // If we loaded Foo.h, we want to make sure Foo.cpp is indexed.
   if (NewFile && BackgroundIdx)

clang-tools-extra/clangd/ClangdServer.h

@@ -16,6 +16,7 @@
 #include "FeatureModule.h"
 #include "GlobalCompilationDatabase.h"
 #include "Hover.h"
+#include "ModulesBuilder.h"
 #include "Protocol.h"
 #include "SemanticHighlighting.h"
 #include "TUScheduler.h"
@@ -112,6 +113,9 @@ class ClangdServer {
     /// This throttler controls which preambles may be built at a given time.
     clangd::PreambleThrottler *PreambleThrottler = nullptr;
 
+    /// Manages to build module files.
+    ModulesBuilder *ModulesManager = nullptr;
+
     /// If true, ClangdServer builds a dynamic in-memory index for symbols in
     /// opened files and uses the index to augment code completion results.
     bool BuildDynamicSymbolIndex = false;
@@ -477,6 +481,8 @@ class ClangdServer {
   std::unique_ptr<BackgroundIndex> BackgroundIdx;
   // Storage for merged views of the various indexes.
   std::vector<std::unique_ptr<SymbolIndex>> MergedIdx;
+  // Manage module files.
+  ModulesBuilder *ModulesManager = nullptr;
 
   // When set, provides clang-tidy options for a specific file.
   TidyProviderRef ClangTidyProvider;

clang-tools-extra/clangd/Compiler.h

@@ -16,6 +16,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_COMPILER_H
 
 #include "FeatureModule.h"
+#include "ModulesBuilder.h"
 #include "TidyProvider.h"
 #include "index/Index.h"
 #include "support/ThreadsafeFS.h"
@@ -60,6 +61,8 @@ struct ParseInputs {
   TidyProviderRef ClangTidyProvider = {};
   // Used to acquire ASTListeners when parsing files.
   FeatureModuleSet *FeatureModules = nullptr;
+  // Used to build and manage (C++) modules.
+  ModulesBuilder *ModulesManager = nullptr;
 };
 
 /// Clears \p CI from options that are not supported by clangd, like codegen or

clang-tools-extra/clangd/GlobalCompilationDatabase.cpp

@@ -9,6 +9,8 @@
 #include "GlobalCompilationDatabase.h"
 #include "Config.h"
 #include "FS.h"
+#include "ProjectModules.h"
+#include "ScanningProjectModules.h"
 #include "SourceCode.h"
 #include "support/Logger.h"
 #include "support/Path.h"
@@ -740,6 +742,20 @@ DirectoryBasedGlobalCompilationDatabase::getProjectInfo(PathRef File) const {
   return Res->PI;
 }
 
+std::unique_ptr<ProjectModules>
+DirectoryBasedGlobalCompilationDatabase::getProjectModules(PathRef File) const {
+  CDBLookupRequest Req;
+  Req.FileName = File;
+  Req.ShouldBroadcast = false;
+  Req.FreshTime = Req.FreshTimeMissing =
+      std::chrono::steady_clock::time_point::min();
+  auto Res = lookupCDB(Req);
+  if (!Res)
+    return {};
+
+  return scanningProjectModules(Res->CDB, Opts.TFS);
+}
+
 OverlayCDB::OverlayCDB(const GlobalCompilationDatabase *Base,
                        std::vector<std::string> FallbackFlags,
                        CommandMangler Mangler)
@@ -832,6 +848,13 @@ std::optional<ProjectInfo> DelegatingCDB::getProjectInfo(PathRef File) const {
   return Base->getProjectInfo(File);
 }
 
+std::unique_ptr<ProjectModules>
+DelegatingCDB::getProjectModules(PathRef File) const {
+  if (!Base)
+    return nullptr;
+  return Base->getProjectModules(File);
+}
+
 tooling::CompileCommand DelegatingCDB::getFallbackCommand(PathRef File) const {
   if (!Base)
     return GlobalCompilationDatabase::getFallbackCommand(File);

clang-tools-extra/clangd/GlobalCompilationDatabase.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_GLOBALCOMPILATIONDATABASE_H
 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_GLOBALCOMPILATIONDATABASE_H
 
+#include "ProjectModules.h"
 #include "support/Function.h"
 #include "support/Path.h"
 #include "support/Threading.h"
@@ -45,6 +46,12 @@ class GlobalCompilationDatabase {
     return std::nullopt;
   }
 
+  /// Get the modules in the closest project to \p File
+  virtual std::unique_ptr<ProjectModules>
+  getProjectModules(PathRef File) const {
+    return nullptr;
+  }
+
   /// Makes a guess at how to build a file.
   /// The default implementation just runs clang on the file.
   /// Clangd should treat the results as unreliable.
@@ -76,6 +83,9 @@ class DelegatingCDB : public GlobalCompilationDatabase {
 
   std::optional<ProjectInfo> getProjectInfo(PathRef File) const override;
 
+  std::unique_ptr<ProjectModules>
+  getProjectModules(PathRef File) const override;
+
   tooling::CompileCommand getFallbackCommand(PathRef File) const override;
 
   bool blockUntilIdle(Deadline D) const override;
@@ -122,6 +132,9 @@ class DirectoryBasedGlobalCompilationDatabase
   /// \p File's parents.
   std::optional<ProjectInfo> getProjectInfo(PathRef File) const override;
 
+  std::unique_ptr<ProjectModules>
+  getProjectModules(PathRef File) const override;
+
   bool blockUntilIdle(Deadline Timeout) const override;
 
 private: