//===--- tools/extra/clang-tidy/ClangTidyMain.cpp - Clang tidy tool -------===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
///  \file This file implements a clang-tidy tool.
///
///  This tool uses the Clang Tooling infrastructure, see
///    http://clang.llvm.org/docs/HowToSetupToolingForLLVM.html
///  for details on setting it up with LLVM source tree.
///
//===----------------------------------------------------------------------===//

#include "ClangTidyMain.h"
#include "../ClangTidy.h"
#include "../ClangTidyForceLinker.h"
#include "../GlobList.h"
#include "clang/Tooling/CommonOptionsParser.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/PluginLoader.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/WithColor.h"
#include <optional>

using namespace clang::tooling;
using namespace llvm;

static cl::desc desc(StringRef description) {
  return cl::desc(description.ltrim());
}

static cl::OptionCategory ClangTidyCategory("clang-tidy options");

static cl::extrahelp CommonHelp(CommonOptionsParser::HelpMessage);
static cl::extrahelp ClangTidyHelp(R"(
Configuration files:
  clang-tidy attempts to read configuration for each source file from a
  .clang-tidy file located in the closest parent directory of the source
  file. The .clang-tidy file is specified in YAML format. If any configuration
  options have a corresponding command-line option, command-line option takes
  precedence.

  The following configuration options may be used in a .clang-tidy file:

  CheckOptions                 - List of key-value pairs defining check-specific
                                 options. Example:
                                   CheckOptions:
                                     some-check.SomeOption: 'some value'
  Checks                       - Same as '--checks'. Additionally, the list of
                                 globs can be specified as a list instead of a
                                 string.
  ExtraArgs                    - Same as '--extra-args'.
  ExtraArgsBefore              - Same as '--extra-args-before'.
  FormatStyle                  - Same as '--format-style'.
  HeaderFileExtensions         - File extensions to consider to determine if a
                                 given diagnostic is located in a header file.
  HeaderFilterRegex            - Same as '--header-filter-regex'.
  ImplementationFileExtensions - File extensions to consider to determine if a
                                 given diagnostic is located in an
                                 implementation file.
  InheritParentConfig          - If this option is true in a config file, the
                                 configuration file in the parent directory
                                 (if any exists) will be taken and the current
                                 config file will be applied on top of the
                                 parent one.
  SystemHeaders                - Same as '--system-headers'.
  UseColor                     - Same as '--use-color'.
  User                         - Specifies the name or e-mail of the user
                                 running clang-tidy. This option is used, for
                                 example, to place the correct user name in
                                 TODO() comments in the relevant check.
  WarningsAsErrors             - Same as '--warnings-as-errors'.

  The effective configuration can be inspected using --dump-config:

    $ clang-tidy --dump-config
    ---
    Checks:                       '-*,some-check'
    WarningsAsErrors:             ''
    HeaderFileExtensions:         ['', 'h','hh','hpp','hxx']
    ImplementationFileExtensions: ['c','cc','cpp','cxx']
    HeaderFilterRegex:            ''
    FormatStyle:                  none
    InheritParentConfig:          true
    User:                         user
    CheckOptions:
      some-check.SomeOption: 'some value'
    ...

)");

const char DefaultChecks[] = // Enable these checks by default:
    "clang-diagnostic-*,"    //   * compiler diagnostics
    "clang-analyzer-*";      //   * Static Analyzer checks

static cl::opt<std::string> Checks("checks", desc(R"(
Comma-separated list of globs with optional '-'
prefix. Globs are processed in order of
appearance in the list. Globs without '-'
prefix add checks with matching names to the
set, globs with the '-' prefix remove checks
with matching names from the set of enabled
checks. This option's value is appended to the
value of the 'Checks' option in .clang-tidy
file, if any.
)"),
                                   cl::init(""), cl::cat(ClangTidyCategory));

static cl::opt<std::string> WarningsAsErrors("warnings-as-errors", desc(R"(
Upgrades warnings to errors. Same format as
'-checks'.
This option's value is appended to the value of
the 'WarningsAsErrors' option in .clang-tidy
file, if any.
)"),
                                             cl::init(""),
                                             cl::cat(ClangTidyCategory));

static cl::opt<std::string> HeaderFilter("header-filter", desc(R"(
Regular expression matching the names of the
headers to output diagnostics from. Diagnostics
from the main file of each translation unit are
always displayed.
Can be used together with -line-filter.
This option overrides the 'HeaderFilterRegex'
option in .clang-tidy file, if any.
)"),
                                         cl::init(""),
                                         cl::cat(ClangTidyCategory));

static cl::opt<bool> SystemHeaders("system-headers", desc(R"(
Display the errors from system headers.
This option overrides the 'SystemHeaders' option
in .clang-tidy file, if any.
)"),
                                   cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<std::string> LineFilter("line-filter", desc(R"(
List of files with line ranges to filter the
warnings. Can be used together with
-header-filter. The format of the list is a
JSON array of objects:
  [
    {"name":"file1.cpp","lines":[[1,3],[5,7]]},
    {"name":"file2.h"}
  ]
)"),
                                       cl::init(""),
                                       cl::cat(ClangTidyCategory));

static cl::opt<bool> Fix("fix", desc(R"(
Apply suggested fixes. Without -fix-errors
clang-tidy will bail out if any compilation
errors were found.
)"),
                         cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<bool> FixErrors("fix-errors", desc(R"(
Apply suggested fixes even if compilation
errors were found. If compiler errors have
attached fix-its, clang-tidy will apply them as
well.
)"),
                               cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<bool> FixNotes("fix-notes", desc(R"(
If a warning has no fix, but a single fix can
be found through an associated diagnostic note,
apply the fix.
Specifying this flag will implicitly enable the
'--fix' flag.
)"),
                              cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<std::string> FormatStyle("format-style", desc(R"(
Style for formatting code around applied fixes:
  - 'none' (default) turns off formatting
  - 'file' (literally 'file', not a placeholder)
    uses .clang-format file in the closest parent
    directory
  - '{ <json> }' specifies options inline, e.g.
    -format-style='{BasedOnStyle: llvm, IndentWidth: 8}'
  - 'llvm', 'google', 'webkit', 'mozilla'
See clang-format documentation for the up-to-date
information about formatting styles and options.
This option overrides the 'FormatStyle` option in
.clang-tidy file, if any.
)"),
                                        cl::init("none"),
                                        cl::cat(ClangTidyCategory));

static cl::opt<bool> ListChecks("list-checks", desc(R"(
List all enabled checks and exit. Use with
-checks=* to list all available checks.
)"),
                                cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<bool> ExplainConfig("explain-config", desc(R"(
For each enabled check explains, where it is
enabled, i.e. in clang-tidy binary, command
line or a specific configuration file.
)"),
                                   cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<std::string> Config("config", desc(R"(
Specifies a configuration in YAML/JSON format:
  -config="{Checks: '*',
            CheckOptions: {x: y}}"
When the value is empty, clang-tidy will
attempt to find a file named .clang-tidy for
each source file in its parent directories.
)"),
                                   cl::init(""), cl::cat(ClangTidyCategory));

static cl::opt<std::string> ConfigFile("config-file", desc(R"(
Specify the path of .clang-tidy or custom config file:
 e.g. --config-file=/some/path/myTidyConfigFile
This option internally works exactly the same way as
 --config option after reading specified config file.
Use either --config-file or --config, not both.
)"),
                                       cl::init(""),
                                       cl::cat(ClangTidyCategory));

static cl::opt<bool> DumpConfig("dump-config", desc(R"(
Dumps configuration in the YAML format to
stdout. This option can be used along with a
file name (and '--' if the file is outside of a
project with configured compilation database).
The configuration used for this file will be
printed.
Use along with -checks=* to include
configuration of all checks.
)"),
                                cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<bool> EnableCheckProfile("enable-check-profile", desc(R"(
Enable per-check timing profiles, and print a
report to stderr.
)"),
                                        cl::init(false),
                                        cl::cat(ClangTidyCategory));

static cl::opt<std::string> StoreCheckProfile("store-check-profile", desc(R"(
By default reports are printed in tabulated
format to stderr. When this option is passed,
these per-TU profiles are instead stored as JSON.
)"),
                                              cl::value_desc("prefix"),
                                              cl::cat(ClangTidyCategory));

/// This option allows enabling the experimental alpha checkers from the static
/// analyzer. This option is set to false and not visible in help, because it is
/// highly not recommended for users.
static cl::opt<bool>
    AllowEnablingAnalyzerAlphaCheckers("allow-enabling-analyzer-alpha-checkers",
                                       cl::init(false), cl::Hidden,
                                       cl::cat(ClangTidyCategory));

static cl::opt<std::string> ExportFixes("export-fixes", desc(R"(
YAML file to store suggested fixes in. The
stored fixes can be applied to the input source
code with clang-apply-replacements.
)"),
                                        cl::value_desc("filename"),
                                        cl::cat(ClangTidyCategory));

static cl::opt<bool> Quiet("quiet", desc(R"(
Run clang-tidy in quiet mode. This suppresses
printing statistics about ignored warnings and
warnings treated as errors if the respective
options are specified.
)"),
                           cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<std::string> VfsOverlay("vfsoverlay", desc(R"(
Overlay the virtual filesystem described by file
over the real file system.
)"),
                                       cl::value_desc("filename"),
                                       cl::cat(ClangTidyCategory));

static cl::opt<bool> UseColor("use-color", desc(R"(
Use colors in diagnostics. If not set, colors
will be used if the terminal connected to
standard output supports colors.
This option overrides the 'UseColor' option in
.clang-tidy file, if any.
)"),
                              cl::init(false), cl::cat(ClangTidyCategory));

static cl::opt<bool> VerifyConfig("verify-config", desc(R"(
Check the config files to ensure each check and
option is recognized.
)"),
                                  cl::init(false), cl::cat(ClangTidyCategory));

namespace clang::tidy {

static void printStats(const ClangTidyStats &Stats) {
  if (Stats.errorsIgnored()) {
    llvm::errs() << "Suppressed " << Stats.errorsIgnored() << " warnings (";
    StringRef Separator = "";
    if (Stats.ErrorsIgnoredNonUserCode) {
      llvm::errs() << Stats.ErrorsIgnoredNonUserCode << " in non-user code";
      Separator = ", ";
    }
    if (Stats.ErrorsIgnoredLineFilter) {
      llvm::errs() << Separator << Stats.ErrorsIgnoredLineFilter
                   << " due to line filter";
      Separator = ", ";
    }
    if (Stats.ErrorsIgnoredNOLINT) {
      llvm::errs() << Separator << Stats.ErrorsIgnoredNOLINT << " NOLINT";
      Separator = ", ";
    }
    if (Stats.ErrorsIgnoredCheckFilter)
      llvm::errs() << Separator << Stats.ErrorsIgnoredCheckFilter
                   << " with check filters";
    llvm::errs() << ").\n";
    if (Stats.ErrorsIgnoredNonUserCode)
      llvm::errs() << "Use -header-filter=.* to display errors from all "
                      "non-system headers. Use -system-headers to display "
                      "errors from system headers as well.\n";
  }
}

static std::unique_ptr<ClangTidyOptionsProvider> createOptionsProvider(
   llvm::IntrusiveRefCntPtr<vfs::FileSystem> FS) {
  ClangTidyGlobalOptions GlobalOptions;
  if (std::error_code Err = parseLineFilter(LineFilter, GlobalOptions)) {
    llvm::errs() << "Invalid LineFilter: " << Err.message() << "\n\nUsage:\n";
    llvm::cl::PrintHelpMessage(/*Hidden=*/false, /*Categorized=*/true);
    return nullptr;
  }

  ClangTidyOptions DefaultOptions;
  DefaultOptions.Checks = DefaultChecks;
  DefaultOptions.WarningsAsErrors = "";
  DefaultOptions.HeaderFilterRegex = HeaderFilter;
  DefaultOptions.SystemHeaders = SystemHeaders;
  DefaultOptions.FormatStyle = FormatStyle;
  DefaultOptions.User = llvm::sys::Process::GetEnv("USER");
  // USERNAME is used on Windows.
  if (!DefaultOptions.User)
    DefaultOptions.User = llvm::sys::Process::GetEnv("USERNAME");

  ClangTidyOptions OverrideOptions;
  if (Checks.getNumOccurrences() > 0)
    OverrideOptions.Checks = Checks;
  if (WarningsAsErrors.getNumOccurrences() > 0)
    OverrideOptions.WarningsAsErrors = WarningsAsErrors;
  if (HeaderFilter.getNumOccurrences() > 0)
    OverrideOptions.HeaderFilterRegex = HeaderFilter;
  if (SystemHeaders.getNumOccurrences() > 0)
    OverrideOptions.SystemHeaders = SystemHeaders;
  if (FormatStyle.getNumOccurrences() > 0)
    OverrideOptions.FormatStyle = FormatStyle;
  if (UseColor.getNumOccurrences() > 0)
    OverrideOptions.UseColor = UseColor;

  auto LoadConfig =
      [&](StringRef Configuration,
          StringRef Source) -> std::unique_ptr<ClangTidyOptionsProvider> {
    llvm::ErrorOr<ClangTidyOptions> ParsedConfig =
        parseConfiguration(MemoryBufferRef(Configuration, Source));
    if (ParsedConfig)
      return std::make_unique<ConfigOptionsProvider>(
          std::move(GlobalOptions),
          ClangTidyOptions::getDefaults().merge(DefaultOptions, 0),
          std::move(*ParsedConfig), std::move(OverrideOptions), std::move(FS));
    llvm::errs() << "Error: invalid configuration specified.\n"
                 << ParsedConfig.getError().message() << "\n";
    return nullptr;
  };

  if (ConfigFile.getNumOccurrences() > 0) {
    if (Config.getNumOccurrences() > 0) {
      llvm::errs() << "Error: --config-file and --config are "
                      "mutually exclusive. Specify only one.\n";
      return nullptr;
    }

    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
        llvm::MemoryBuffer::getFile(ConfigFile);
    if (std::error_code EC = Text.getError()) {
      llvm::errs() << "Error: can't read config-file '" << ConfigFile
                   << "': " << EC.message() << "\n";
      return nullptr;
    }

    return LoadConfig((*Text)->getBuffer(), ConfigFile);
  }

  if (Config.getNumOccurrences() > 0)
    return LoadConfig(Config, "<command-line-config>");

  return std::make_unique<FileOptionsProvider>(
      std::move(GlobalOptions), std::move(DefaultOptions),
      std::move(OverrideOptions), std::move(FS));
}

llvm::IntrusiveRefCntPtr<vfs::FileSystem>
getVfsFromFile(const std::string &OverlayFile,
               llvm::IntrusiveRefCntPtr<vfs::FileSystem> BaseFS) {
  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buffer =
      BaseFS->getBufferForFile(OverlayFile);
  if (!Buffer) {
    llvm::errs() << "Can't load virtual filesystem overlay file '"
                 << OverlayFile << "': " << Buffer.getError().message()
                 << ".\n";
    return nullptr;
  }

  IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getVFSFromYAML(
      std::move(Buffer.get()), /*DiagHandler*/ nullptr, OverlayFile);
  if (!FS) {
    llvm::errs() << "Error: invalid virtual filesystem overlay file '"
                 << OverlayFile << "'.\n";
    return nullptr;
  }
  return FS;
}

static StringRef closest(StringRef Value, const StringSet<> &Allowed) {
  unsigned MaxEdit = 5U;
  StringRef Closest;
  for (auto Item : Allowed.keys()) {
    unsigned Cur = Value.edit_distance_insensitive(Item, true, MaxEdit);
    if (Cur < MaxEdit) {
      Closest = Item;
      MaxEdit = Cur;
    }
  }
  return Closest;
}

static constexpr StringLiteral VerifyConfigWarningEnd = " [-verify-config]\n";

static bool verifyChecks(const StringSet<> &AllChecks, StringRef CheckGlob,
                         StringRef Source) {
  llvm::StringRef Cur, Rest;
  bool AnyInvalid = false;
  for (std::tie(Cur, Rest) = CheckGlob.split(',');
       !(Cur.empty() && Rest.empty()); std::tie(Cur, Rest) = Rest.split(',')) {
    Cur = Cur.trim();
    if (Cur.empty())
      continue;
    Cur.consume_front("-");
    if (Cur.startswith("clang-diagnostic"))
      continue;
    if (Cur.contains('*')) {
      SmallString<128> RegexText("^");
      StringRef MetaChars("()^$|*+?.[]\\{}");
      for (char C : Cur) {
        if (C == '*')
          RegexText.push_back('.');
        else if (MetaChars.contains(C))
          RegexText.push_back('\\');
        RegexText.push_back(C);
      }
      RegexText.push_back('$');
      llvm::Regex Glob(RegexText);
      std::string Error;
      if (!Glob.isValid(Error)) {
        AnyInvalid = true;
        llvm::WithColor::error(llvm::errs(), Source)
            << "building check glob '" << Cur << "' " << Error << "'\n";
        continue;
      }
      if (llvm::none_of(AllChecks.keys(),
                        [&Glob](StringRef S) { return Glob.match(S); })) {
        AnyInvalid = true;
        llvm::WithColor::warning(llvm::errs(), Source)
            << "check glob '" << Cur << "' doesn't match any known check"
            << VerifyConfigWarningEnd;
      }
    } else {
      if (AllChecks.contains(Cur))
        continue;
      AnyInvalid = true;
      llvm::raw_ostream &Output = llvm::WithColor::warning(llvm::errs(), Source)
                                  << "unknown check '" << Cur << '\'';
      llvm::StringRef Closest = closest(Cur, AllChecks);
      if (!Closest.empty())
        Output << "; did you mean '" << Closest << '\'';
      Output << VerifyConfigWarningEnd;
    }
  }
  return AnyInvalid;
}

static bool verifyFileExtensions(
    const std::vector<std::string> &HeaderFileExtensions,
    const std::vector<std::string> &ImplementationFileExtensions,
    StringRef Source) {
  bool AnyInvalid = false;
  for (const auto &HeaderExtension : HeaderFileExtensions) {
    for (const auto &ImplementationExtension : ImplementationFileExtensions) {
      if (HeaderExtension == ImplementationExtension) {
        AnyInvalid = true;
        auto &Output = llvm::WithColor::warning(llvm::errs(), Source)
                       << "HeaderFileExtension '" << HeaderExtension << '\''
                       << " is the same as ImplementationFileExtension '"
                       << ImplementationExtension << '\'';
        Output << VerifyConfigWarningEnd;
      }
    }
  }
  return AnyInvalid;
}

int clangTidyMain(int argc, const char **argv) {
  llvm::InitLLVM X(argc, argv);

  // Enable help for -load option, if plugins are enabled.
  if (cl::Option *LoadOpt = cl::getRegisteredOptions().lookup("load"))
    LoadOpt->addCategory(ClangTidyCategory);

  llvm::Expected<CommonOptionsParser> OptionsParser =
      CommonOptionsParser::create(argc, argv, ClangTidyCategory,
                                  cl::ZeroOrMore);
  if (!OptionsParser) {
    llvm::WithColor::error() << llvm::toString(OptionsParser.takeError());
    return 1;
  }

  llvm::IntrusiveRefCntPtr<vfs::OverlayFileSystem> BaseFS(
      new vfs::OverlayFileSystem(vfs::getRealFileSystem()));

  if (!VfsOverlay.empty()) {
    IntrusiveRefCntPtr<vfs::FileSystem> VfsFromFile =
        getVfsFromFile(VfsOverlay, BaseFS);
    if (!VfsFromFile)
      return 1;
    BaseFS->pushOverlay(std::move(VfsFromFile));
  }

  auto OwningOptionsProvider = createOptionsProvider(BaseFS);
  auto *OptionsProvider = OwningOptionsProvider.get();
  if (!OptionsProvider)
    return 1;

  auto MakeAbsolute = [](const std::string &Input) -> SmallString<256> {
    if (Input.empty())
      return {};
    SmallString<256> AbsolutePath(Input);
    if (std::error_code EC = llvm::sys::fs::make_absolute(AbsolutePath)) {
      llvm::errs() << "Can't make absolute path from " << Input << ": "
                   << EC.message() << "\n";
    }
    return AbsolutePath;
  };

  SmallString<256> ProfilePrefix = MakeAbsolute(StoreCheckProfile);

  StringRef FileName("dummy");
  auto PathList = OptionsParser->getSourcePathList();
  if (!PathList.empty()) {
    FileName = PathList.front();
  }

  SmallString<256> FilePath = MakeAbsolute(std::string(FileName));

  ClangTidyOptions EffectiveOptions = OptionsProvider->getOptions(FilePath);
  std::vector<std::string> EnabledChecks =
      getCheckNames(EffectiveOptions, AllowEnablingAnalyzerAlphaCheckers);

  if (ExplainConfig) {
    // FIXME: Show other ClangTidyOptions' fields, like ExtraArg.
    std::vector<clang::tidy::ClangTidyOptionsProvider::OptionsSource>
        RawOptions = OptionsProvider->getRawOptions(FilePath);
    for (const std::string &Check : EnabledChecks) {
      for (const auto &[Opts, Source] : llvm::reverse(RawOptions)) {
        if (Opts.Checks && GlobList(*Opts.Checks).contains(Check)) {
          llvm::outs() << "'" << Check << "' is enabled in the " << Source
                       << ".\n";
          break;
        }
      }
    }
    return 0;
  }

  if (ListChecks) {
    if (EnabledChecks.empty()) {
      llvm::errs() << "No checks enabled.\n";
      return 1;
    }
    llvm::outs() << "Enabled checks:";
    for (const auto &CheckName : EnabledChecks)
      llvm::outs() << "\n    " << CheckName;
    llvm::outs() << "\n\n";
    return 0;
  }

  if (DumpConfig) {
    EffectiveOptions.CheckOptions =
        getCheckOptions(EffectiveOptions, AllowEnablingAnalyzerAlphaCheckers);
    llvm::outs() << configurationAsText(ClangTidyOptions::getDefaults().merge(
                        EffectiveOptions, 0))
                 << "\n";
    return 0;
  }

  if (VerifyConfig) {
    std::vector<ClangTidyOptionsProvider::OptionsSource> RawOptions =
        OptionsProvider->getRawOptions(FileName);
    NamesAndOptions Valid =
        getAllChecksAndOptions(AllowEnablingAnalyzerAlphaCheckers);
    bool AnyInvalid = false;
    for (const auto &[Opts, Source] : RawOptions) {
      if (Opts.Checks)
        AnyInvalid |= verifyChecks(Valid.Names, *Opts.Checks, Source);

      if (Opts.HeaderFileExtensions && Opts.ImplementationFileExtensions)
        AnyInvalid |=
            verifyFileExtensions(*Opts.HeaderFileExtensions,
                                 *Opts.ImplementationFileExtensions, Source);

      for (auto Key : Opts.CheckOptions.keys()) {
        if (Valid.Options.contains(Key))
          continue;
        AnyInvalid = true;
        auto &Output = llvm::WithColor::warning(llvm::errs(), Source)
                       << "unknown check option '" << Key << '\'';
        llvm::StringRef Closest = closest(Key, Valid.Options);
        if (!Closest.empty())
          Output << "; did you mean '" << Closest << '\'';
        Output << VerifyConfigWarningEnd;
      }
    }
    if (AnyInvalid)
      return 1;
    llvm::outs() << "No config errors detected.\n";
    return 0;
  }

  if (EnabledChecks.empty()) {
    llvm::errs() << "Error: no checks enabled.\n";
    llvm::cl::PrintHelpMessage(/*Hidden=*/false, /*Categorized=*/true);
    return 1;
  }

  if (PathList.empty()) {
    llvm::errs() << "Error: no input files specified.\n";
    llvm::cl::PrintHelpMessage(/*Hidden=*/false, /*Categorized=*/true);
    return 1;
  }

  llvm::InitializeAllTargetInfos();
  llvm::InitializeAllTargetMCs();
  llvm::InitializeAllAsmParsers();

  ClangTidyContext Context(std::move(OwningOptionsProvider),
                           AllowEnablingAnalyzerAlphaCheckers);
  std::vector<ClangTidyError> Errors =
      runClangTidy(Context, OptionsParser->getCompilations(), PathList, BaseFS,
                   FixNotes, EnableCheckProfile, ProfilePrefix);
  bool FoundErrors = llvm::any_of(Errors, [](const ClangTidyError &E) {
    return E.DiagLevel == ClangTidyError::Error;
  });

  // --fix-errors and --fix-notes imply --fix.
  FixBehaviour Behaviour = FixNotes             ? FB_FixNotes
                           : (Fix || FixErrors) ? FB_Fix
                                                : FB_NoFix;

  const bool DisableFixes = FoundErrors && !FixErrors;

  unsigned WErrorCount = 0;

  handleErrors(Errors, Context, DisableFixes ? FB_NoFix : Behaviour,
               WErrorCount, BaseFS);

  if (!ExportFixes.empty() && !Errors.empty()) {
    std::error_code EC;
    llvm::raw_fd_ostream OS(ExportFixes, EC, llvm::sys::fs::OF_None);
    if (EC) {
      llvm::errs() << "Error opening output file: " << EC.message() << '\n';
      return 1;
    }
    exportReplacements(FilePath.str(), Errors, OS);
  }

  if (!Quiet) {
    printStats(Context.getStats());
    if (DisableFixes && Behaviour != FB_NoFix)
      llvm::errs()
          << "Found compiler errors, but -fix-errors was not specified.\n"
             "Fixes have NOT been applied.\n\n";
  }

  if (WErrorCount) {
    if (!Quiet) {
      StringRef Plural = WErrorCount == 1 ? "" : "s";
      llvm::errs() << WErrorCount << " warning" << Plural << " treated as error"
                   << Plural << "\n";
    }
    return 1;
  }

  if (FoundErrors) {
    // TODO: Figure out when zero exit code should be used with -fix-errors:
    //   a. when a fix has been applied for an error
    //   b. when a fix has been applied for all errors
    //   c. some other condition.
    // For now always returning zero when -fix-errors is used.
    if (FixErrors)
      return 0;
    if (!Quiet)
      llvm::errs() << "Found compiler error(s).\n";
    return 1;
  }

  return 0;
}

} // namespace clang::tidy