[clang-doc] Generate an HTML index file

[DiegoAstiazaran]

Summary

clang-doc now generates a file that contains only an index to all the infos that can be used as the landing page for the generated website.

clang-tools-extra/clang-doc/HTMLGenerator.cpp

std::function<void(Index)> IndexToJSON = [&](Index I) {
     });
   };
   OS << "var JsonIndex = `\n";
   IndexToJSON(CDCtx.Idx);
   OS << "`;\n";
   return true;
 }
 
+static bool GenIndex(const ClangDocContext &CDCtx) {
+  std::error_code FileErr, OK;
+  llvm::SmallString<128> IndexPath;
+  llvm::sys::path::native(CDCtx.OutDirectory, IndexPath);
+  llvm::sys::path::append(IndexPath, "index.html");
+  llvm::raw_fd_ostream IndexOS(IndexPath, FileErr, llvm::sys::fs::F_None);
+  if (FileErr != OK) {
+    llvm::errs() << "Error creating main index: " << FileErr.message() << "\n";
+    return false;
+  }
+  HTMLFile F;
+  std::vector<std::unique_ptr<TagNode>> BasicNodes =
+      genCommonFileNodes("Index", "", CDCtx);
+  AppendVector(std::move(BasicNodes), F.Children);
+  F.Render(IndexOS);
+  return true;
+}
+
 static bool CopyFile(StringRef FilePath, StringRef OutDirectory) {
   llvm::SmallString<128> PathWrite;
   llvm::sys::path::native(OutDirectory, PathWrite);
   llvm::sys::path::append(PathWrite, llvm::sys::path::filename(FilePath));
   llvm::SmallString<128> PathRead;
   llvm::sys::path::native(FilePath, PathRead);
   std::error_code OK;
   std::error_code FileErr = llvm::sys::fs::copy_file(PathRead, PathWrite);
   if (FileErr != OK) {
     llvm::errs() << "Error creating file "
                  << llvm::sys::path::filename(FilePath) << ": "
                  << FileErr.message() << "\n";
     return false;
   }
   return true;
 }
 
 bool HTMLGenerator::createResources(ClangDocContext &CDCtx) {
-  if (!SerializeIndex(CDCtx))
+  if (!SerializeIndex(CDCtx) || !GenIndex(CDCtx))
     return false;
   for (const auto &FilePath : CDCtx.UserStylesheets)
     if (!CopyFile(FilePath, CDCtx.OutDirectory))
       return false;
   for (const auto &FilePath : CDCtx.FilesToCopy)
     if (!CopyFile(FilePath, CDCtx.OutDirectory))
       return false;
   return true;