clang-tools-extra/clangd/ModulesBuilder.h

   1 //===----------------- ModulesBuilder.h --------------------------*- C++-*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Experimental support for C++20 Modules.
  10 //
  11 // Currently we simplify the implementations by preventing reusing module files
  12 // across different versions and different source files. But this is clearly a
  13 // waste of time and space in the end of the day.
  14 //
  15 // TODO: Supporting reusing module files across different versions and
  16 // different source files.
  17 //
  18 //===----------------------------------------------------------------------===//
  19
  20 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_MODULES_BUILDER_H
  21 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_MODULES_BUILDER_H
  22
  23 #include "GlobalCompilationDatabase.h"
  24 #include "ProjectModules.h"
  25 #include "support/Path.h"
  26 #include "support/ThreadsafeFS.h"
  27 #include "clang/Frontend/CompilerInvocation.h"
  28 #include "llvm/ADT/SmallString.h"
  29 #include <memory>
  30
  31 namespace clang {
  32 namespace clangd {
  33
  34 /// Store all the needed module files information to parse a single
  35 /// source file. e.g.,
  36 ///
  37 ///   ```
  38 ///   // a.cppm
  39 ///   export module a;
  40 ///
  41 ///   // b.cppm
  42 ///   export module b;
  43 ///   import a;
  44 ///
  45 ///   // c.cppm
  46 ///   export module c;
  47 ///   import b;
  48 ///   ```
  49 ///
  50 /// For the source file `c.cppm`, an instance of the class will store
  51 /// the module files for `a.cppm` and `b.cppm`. But the module file for `c.cppm`
  52 /// won't be stored. Since it is not needed to parse `c.cppm`.
  53 ///
  54 /// Users should only get PrerequisiteModules from
  55 /// `ModulesBuilder::buildPrerequisiteModulesFor(...)`.
  56 ///
  57 /// Users can detect whether the PrerequisiteModules is still up to date by
  58 /// calling the `canReuse()` member function.
  59 ///
  60 /// The users should call `adjustHeaderSearchOptions(...)` to update the
  61 /// compilation commands to select the built module files first. Before calling
  62 /// `adjustHeaderSearchOptions()`, users should call `canReuse()` first to check
  63 /// if all the stored module files are valid. In case they are not valid,
  64 /// users should call `ModulesBuilder::buildPrerequisiteModulesFor(...)` again
  65 /// to get the new PrerequisiteModules.
  66 class PrerequisiteModules {
  67 public:
  68   /// Change commands to load the module files recorded in this
  69   /// PrerequisiteModules first.
  70   virtual void
  71   adjustHeaderSearchOptions(HeaderSearchOptions &Options) const = 0;
  72
  73   /// Whether or not the built module files are up to date.
  74   /// Note that this can only be used after building the module files.
  75   virtual bool
  76   canReuse(const CompilerInvocation &CI,
  77            llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem>) const = 0;
  78
  79   virtual ~PrerequisiteModules() = default;
  80 };
  81
  82 /// This class handles building module files for a given source file.
  83 ///
  84 /// In the future, we want the class to manage the module files acorss
  85 /// different versions and different source files.
  86 class ModulesBuilder {
  87 public:
  88   ModulesBuilder(const GlobalCompilationDatabase &CDB) : CDB(CDB) {}
  89
  90   ModulesBuilder(const ModulesBuilder &) = delete;
  91   ModulesBuilder(ModulesBuilder &&) = delete;
  92
  93   ModulesBuilder &operator=(const ModulesBuilder &) = delete;
  94   ModulesBuilder &operator=(ModulesBuilder &&) = delete;
  95
  96   std::unique_ptr<PrerequisiteModules>
  97   buildPrerequisiteModulesFor(PathRef File, const ThreadsafeFS &TFS) const;
  98
  99 private:
 100   const GlobalCompilationDatabase &CDB;
 101 };
 102
 103 } // namespace clangd
 104 } // namespace clang
 105
 106 #endif