[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[Chuanqi Xu via cfe-commits]

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@@ -0,0 +1,62 @@
+//===------------------ ProjectModules.h -------------------------*- C++-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ProjectModules.h"
+
+namespace clang {
+namespace clangd {
+
+/// TODO: The existing `ScanningAllProjectModules` is not efficient. See the
+/// comments in ModuleDependencyScanner for detail.
+///
+/// In the future, we wish the build system can provide a well design
+/// compilation database for modules then we can query that new compilation
+/// database directly. Or we need to have a global long-live scanner to detect
+/// the state of each file.
+class ScanningAllProjectModules : public ProjectModules {
+public:
+  ScanningAllProjectModules(std::vector<std::string> &&AllFiles,
+                            const GlobalCompilationDatabase &CDB,
+                            const ThreadsafeFS &TFS)
+      : AllFiles(std::move(AllFiles)), Scanner(CDB, TFS) {}
+
+  ~ScanningAllProjectModules() override = default;
+
+  std::vector<std::string> getRequiredModules(PathRef File) override {
+    return Scanner.getRequiredModules(File);
+  }
+
+  /// RequiredSourceFile is not used intentionally. See the comments of
+  /// ModuleDependencyScanner for detail.
+  PathRef
+  getSourceForModuleName(StringRef ModuleName,
+                         PathRef RequiredSourceFile = PathRef()) override {
+    if (!Scanner.isGlobalScanned())
+      Scanner.globalScan(AllFiles);
+
+    return Scanner.getSourceForModuleName(ModuleName);
+  }
+
+private:
+  std::vector<std::string> AllFiles;
+
+  ModuleDependencyScanner Scanner;
----------------
ChuanqiXu9 wrote:

Done. Good idea. I like it.

https://github.com/llvm/llvm-project/pull/66462