[clangd] Expose include cleaner interface in clangd

[serge-sans-paille]

Summary

This gives it the same status as other pieces of clangd and paves the way for
other usage.

clang-tools-extra/clangd/ClangdServer.h

public:
   /// Get document highlights for a given position.
   void findDocumentHighlights(PathRef File, Position Pos,
                               Callback<std::vector<DocumentHighlight>> CB);
 
   /// Get code hover for a given position.
   void findHover(PathRef File, Position Pos,
                  Callback<llvm::Optional<HoverInfo>> CB);
 
+  /// Get information about unused includes.
+  void findUnusedIncludes(PathRef File,
+                          Callback<std::vector<const Inclusion *>> CB);
+
   /// Get information about type hierarchy for a given position.
   void typeHierarchy(PathRef File, Position Pos, int Resolve,
                      TypeHierarchyDirection Direction,
                      Callback<llvm::Optional<TypeHierarchyItem>> CB);
 
   /// Resolve type hierarchy item in the given direction.
   void resolveTypeHierarchy(TypeHierarchyItem Item, int Resolve,
                             TypeHierarchyDirection Direction,

clang-tools-extra/clangd/ClangdServer.cpp

 //===--- ClangdServer.cpp - Main clangd server code --------------*- 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 "ClangdServer.h"
 #include "CodeComplete.h"
 #include "Config.h"
 #include "Diagnostics.h"
 #include "DumpAST.h"
 #include "FindSymbols.h"
 #include "Format.h"
 #include "HeaderSourceSwitch.h"
+#include "IncludeCleaner.h"
 #include "InlayHints.h"
 #include "ParsedAST.h"
 #include "Preamble.h"
 #include "Protocol.h"
 #include "SemanticHighlighting.h"
 #include "SemanticSelection.h"
 #include "SourceCode.h"
 #include "TUScheduler.h"
auto Action = [File = File.str(), Pos, CB = std::move(CB),
     format::FormatStyle Style = getFormatStyleForFile(
         File, InpAST->Inputs.Contents, *InpAST->Inputs.TFS);
     CB(clangd::getHover(InpAST->AST, Pos, std::move(Style), Index));
   };
 
   WorkScheduler->runWithAST("Hover", File, std::move(Action), Transient);
 }
 
+void ClangdServer::findUnusedIncludes(
+    PathRef File, Callback<std::vector<const Inclusion *>> CB) {
+  auto Action = [File = File.str(), CB = std::move(CB)](
+                    llvm::Expected<InputsAndAST> InpAST) mutable {
+    if (!InpAST)
+      return CB(InpAST.takeError());
+    CB(clangd::computeUnusedIncludes(InpAST->AST));
+  };
+
+  WorkScheduler->runWithAST("UnusedIncludes", File, std::move(Action),
+                            Transient);
+}
+
 void ClangdServer::typeHierarchy(PathRef File, Position Pos, int Resolve,
                                  TypeHierarchyDirection Direction,
                                  Callback<Optional<TypeHierarchyItem>> CB) {
   auto Action = [File = File.str(), Pos, Resolve, Direction, CB = std::move(CB),
                  this](Expected<InputsAndAST> InpAST) mutable {
     if (!InpAST)
       return CB(InpAST.takeError());
     CB(clangd::getTypeHierarchy(InpAST->AST, Pos, Resolve, Direction, Index,