[clangd] Support dexp -c "some command"

[sammccall]

Summary

It runs one command and exits.
See D77385 for motivation.

[kbobyrev]

LGTM with a couple of nits

clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp

85

Nit: capitalization

100

nit: const?

328

return !runCommand(...)?

330–332

Maybe also just delete this one since there's some new code anyway.

[sammccall]

clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp

100

we generally don't bother declaring local vars const.

328

I think it's unneccesarily confusing to rely on implicit bool->int conversion in a context where zero means success.

clang-tools-extra/clangd/index/dex/dexp/Dexp.cpp

 //===--- Dexp.cpp - Dex EXPloration tool ------------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements a simple interactive tool which can be used to manually
 // evaluate symbol search quality of Clangd index.
 //
 //===----------------------------------------------------------------------===//
 
 #include "SourceCode.h"
 #include "index/Serialization.h"
 #include "index/dex/Dex.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/LineEditor/LineEditor.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Signals.h"
 
 namespace clang {
 namespace clangd {
 namespace {
 
 llvm::cl::opt<std::string> IndexPath("index-path",
                                      llvm::cl::desc("Path to the index"),
                                      llvm::cl::Positional, llvm::cl::Required);
 
+llvm::cl::opt<std::string>
+    ExecCommand("c", llvm::cl::desc("Command to execute and then exit"));
+
 static const std::string Overview = R"(
 This is an **experimental** interactive tool to process user-provided search
 queries over given symbol collection obtained via clangd-indexer. The
 tool can be used to evaluate search quality of existing index implementations
 and manually construct non-trivial test cases.
 
 Type use "help" request to get information about the details.
 )";

 
 // REPL commands inherit from Command and contain their options as members.
 // Creating a Command populates parser options, parseAndRun() resets them.
 class Command {
   // By resetting the parser options, we lost the standard -help flag.
   llvm::cl::opt<bool, false, llvm::cl::parser<bool>> Help{
       "help", llvm::cl::desc("Display available options"),
       llvm::cl::ValueDisallowed, llvm::cl::cat(llvm::cl::GeneralCategory)};
+  // FIXME: Allow commands to signal failure.
   virtual void run() = 0;
 
 protected:
   const SymbolIndex *Index;
 
 public:
   virtual ~Command() = default;
-  virtual void parseAndRun(llvm::ArrayRef<const char *> Argv,
-                           const char *Overview, const SymbolIndex &Index) {
+  bool parseAndRun(llvm::ArrayRef<const char *> Argv, const char *Overview,
+                   const SymbolIndex &Index) {
     std::string ParseErrs;
     llvm::raw_string_ostream OS(ParseErrs);
     bool Ok = llvm::cl::ParseCommandLineOptions(Argv.size(), Argv.data(),
                                                 Overview, &OS);
+    // must do this before opts are destroyed
+    auto Cleanup = llvm::make_scope_exit(llvm::cl::ResetCommandLineParser);
     if (Help.getNumOccurrences() > 0) {
       // Avoid printing parse errors in this case.
       // (Well, in theory. A bunch get printed to llvm::errs() regardless!)
       llvm::cl::PrintHelpMessage();
-    } else {
-      llvm::outs() << OS.str();
-      if (Ok) {
-        this->Index = &Index;
-        reportTime(Argv[0], [&] { run(); });
-      }
-    }
-    llvm::cl::ResetCommandLineParser(); // must do this before opts are
-                                        // destroyed.
+      return true;
+    }
+
+    return Ok;
   }
 };
 
 // FIXME(kbobyrev): Ideas for more commands:
 // * load/swap/reload index: this would make it possible to get rid of llvm::cl
 //   usages in the tool driver and actually use llvm::cl library in the REPL.
 // * show posting list density histogram (our dump data somewhere so that user
 //   could build one)
std::function<std::unique_ptr<Command>()> Implementation;
     {"refs", "Find references by ID or qualified name",
      std::make_unique<Refs>},
 };
 
 std::unique_ptr<SymbolIndex> openIndex(llvm::StringRef Index) {
   return loadIndex(Index, /*UseDex=*/true);
 }
 
+bool runCommand(std::string Request, const SymbolIndex &Index) {
+  // Split on spaces and add required null-termination.
+  std::replace(Request.begin(), Request.end(), ' ', '\0');
+  llvm::SmallVector<llvm::StringRef, 8> Args;
+  llvm::StringRef(Request).split(Args, '\0', /*MaxSplit=*/-1,
+                                 /*KeepEmpty=*/false);
+  if (Args.empty())
+    return false;
+  if (Args.front() == "help") {
+    llvm::outs() << "dexp - Index explorer\nCommands:\n";
+    for (const auto &C : CommandInfo)
+      llvm::outs() << llvm::formatv("{0,16} - {1}\n", C.Name, C.Description);
+    llvm::outs() << "Get detailed command help with e.g. `find -help`.\n";
+    return true;
+  }
+  llvm::SmallVector<const char *, 8> FakeArgv;
+  for (llvm::StringRef S : Args)
+    FakeArgv.push_back(S.data()); // Terminated by separator or end of string.
+
+  for (const auto &Cmd : CommandInfo) {
+    if (Cmd.Name == Args.front())
+      return Cmd.Implementation()->parseAndRun(FakeArgv, Cmd.Description,
+                                               Index);
+  }
+  llvm::outs() << "Unknown command. Try 'help'.\n";
+  return false;
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
 
 int main(int argc, const char *argv[]) {
   using namespace clang::clangd;
 
   llvm::cl::ParseCommandLineOptions(argc, argv, Overview);
   llvm::cl::ResetCommandLineParser(); // We reuse it for REPL commands.
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
 
   std::unique_ptr<SymbolIndex> Index;
   reportTime("Dex build", [&]() {
     Index = openIndex(IndexPath);
   });
 
   if (!Index) {
     llvm::outs() << "Failed to open the index.\n";
     return -1;
   }
 
-  llvm::LineEditor LE("dexp");
+  if (!ExecCommand.empty())
+    return runCommand(ExecCommand, *Index) ? 0 : 1;
 
-  while (llvm::Optional<std::string> Request = LE.readLine()) {
-    // Split on spaces and add required null-termination.
-    std::replace(Request->begin(), Request->end(), ' ', '\0');
-    llvm::SmallVector<llvm::StringRef, 8> Args;
-    llvm::StringRef(*Request).split(Args, '\0', /*MaxSplit=*/-1,
-                                    /*KeepEmpty=*/false);
-    if (Args.empty())
-      continue;
-    if (Args.front() == "help") {
-      llvm::outs() << "dexp - Index explorer\nCommands:\n";
-      for (const auto &C : CommandInfo)
-        llvm::outs() << llvm::formatv("{0,16} - {1}\n", C.Name, C.Description);
-      llvm::outs() << "Get detailed command help with e.g. `find -help`.\n";
-      continue;
-    }
-    llvm::SmallVector<const char *, 8> FakeArgv;
-    for (llvm::StringRef S : Args)
-      FakeArgv.push_back(S.data()); // Terminated by separator or end of string.
-
-    bool Recognized = false;
-    for (const auto &Cmd : CommandInfo) {
-      if (Cmd.Name == Args.front()) {
-        Recognized = true;
-        Cmd.Implementation()->parseAndRun(FakeArgv, Cmd.Description, *Index);
-        break;
-      }
-    }
-    if (!Recognized)
-      llvm::outs() << "Unknown command. Try 'help'.\n";
-  }
-
-  return 0;
+  llvm::LineEditor LE("dexp");
+  while (llvm::Optional<std::string> Request = LE.readLine())
+    runCommand(std::move(*Request), *Index);
 }