[clangd] Use Contents from inputs in codeComplete and signatureHelp

[simark]

Summary

ClangdServer::{codeComplete,signatureHelp} both use the Contents from
the draft manager. Since we want to move the draft manager from
ClangdServer to ClangdLSPServer, this patch changes those methods to
find the file contents from InputsAndPreamble, which contains the source
passed in previously.

clangd/ClangdServer.cpp

void ClangdServer::codeComplete(PathRef File, Position Pos,
   if (!Latest.Draft)
     return CB(llvm::make_error<llvm::StringError>(
         "codeComplete called for non-added document",
         llvm::errc::invalid_argument));
 
   // Copy PCHs to avoid accessing this->PCHs concurrently
   std::shared_ptr<PCHContainerOperations> PCHs = this->PCHs;
   auto FS = FSProvider.getFileSystem();
-  auto Task = [PCHs, Pos, FS, CodeCompleteOpts](
-                  std::string Contents, Path File, Callback<CompletionList> CB,
+  auto Task = [PCHs, Pos, FS,
+               CodeCompleteOpts](Path File, Callback<CompletionList> CB,
                                  llvm::Expected<InputsAndPreamble> IP) {
     assert(IP && "error when trying to read preamble for codeComplete");
     auto PreambleData = IP->Preamble;
 
     // FIXME(ibiryukov): even if Preamble is non-null, we may want to check
     // both the old and the new version in case only one of them matches.
     CompletionList Result = clangd::codeComplete(
         File, IP->Command, PreambleData ? &PreambleData->Preamble : nullptr,
-        Contents, Pos, FS, PCHs, CodeCompleteOpts);
+        IP->Contents, Pos, FS, PCHs, CodeCompleteOpts);
     CB(std::move(Result));
   };
 
-  WorkScheduler.runWithPreamble(
-      "CodeComplete", File,
-      Bind(Task, std::move(*Latest.Draft), File.str(), std::move(CB)));
+  WorkScheduler.runWithPreamble("CodeComplete", File,
+                                Bind(Task, File.str(), std::move(CB)));
 }
 
 void ClangdServer::signatureHelp(PathRef File, Position Pos,
                                  Callback<SignatureHelp> CB) {
   VersionedDraft Latest = DraftMgr.getDraft(File);
   if (!Latest.Draft)
     return CB(llvm::make_error<llvm::StringError>(
         "signatureHelp is called for non-added document",
         llvm::errc::invalid_argument));
 
   auto PCHs = this->PCHs;
   auto FS = FSProvider.getFileSystem();
-  auto Action = [Pos, FS, PCHs](std::string Contents, Path File,
-                                Callback<SignatureHelp> CB,
+  auto Action = [Pos, FS, PCHs](Path File, Callback<SignatureHelp> CB,
                                 llvm::Expected<InputsAndPreamble> IP) {
     if (!IP)
       return CB(IP.takeError());
 
     auto PreambleData = IP->Preamble;
     CB(clangd::signatureHelp(File, IP->Command,
                              PreambleData ? &PreambleData->Preamble : nullptr,
-                             Contents, Pos, FS, PCHs));
+                             IP->Contents, Pos, FS, PCHs));
   };
 
-  WorkScheduler.runWithPreamble(
-      "SignatureHelp", File,
-      Bind(Action, std::move(*Latest.Draft), File.str(), std::move(CB)));
+  WorkScheduler.runWithPreamble("SignatureHelp", File,
+                                Bind(Action, File.str(), std::move(CB)));
 }
 
 llvm::Expected<tooling::Replacements>
 ClangdServer::formatRange(StringRef Code, PathRef File, Range Rng) {
   size_t Begin = positionToOffset(Code, Rng.start);
   size_t Len = positionToOffset(Code, Rng.end) - Begin;
   return formatCode(Code, File, {tooling::Range(Begin, Len)});
 }