[clang-tidy] Fix llvm-header-guard so that it works with Windows paths

[salman-javed-nz]

Summary

Fixes https://bugs.llvm.org/show_bug.cgi?id=40372.

The llvm-header-guard check does not take into account that the path
separator on Windows is \, not /.

This means that instead of suggesting a header guard in the form of:
LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_FOO_H

it incorrectly suggests:
C:\LLVM_PROJECT\CLANG_TOOLS_EXTRA\CLANG_TIDY\FOO_H

[aaron.ballman]

LGTM, thank you for the fix!

clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp

248–250

Another test case is UNC paths: \\\\?\\C:\\llvm-project\\clang-tools-extra\\clangd\\foo.h (with escapes already added).

[salman-javed-nz]

Unit tests:

• Renamed Samba to SMB
• Added test for UNC paths

[salman-javed-nz]

@aaron.ballman -
I've added the unit test for UNC path as you suggested. Since you've already given the LGTM, I assume you don't need to see the patch again, so I have gone ahead with the commit.
Anyway, I'll be around to address any problems if they crop up.

clang-tools-extra/clang-tidy/llvm/HeaderGuardCheck.cpp

 //===--- HeaderGuardCheck.cpp - clang-tidy --------------------------------===//
 //
 // 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 "HeaderGuardCheck.h"
 #include "clang/Tooling/Tooling.h"
+#include "llvm/Support/Path.h"
 
 namespace clang {
 namespace tidy {
 namespace llvm_check {
 
 LLVMHeaderGuardCheck::LLVMHeaderGuardCheck(StringRef Name,
                                            ClangTidyContext *Context)
     : HeaderGuardCheck(Name, Context) {}
 
 std::string LLVMHeaderGuardCheck::getHeaderGuard(StringRef Filename,
                                                  StringRef OldGuard) {
   std::string Guard = tooling::getAbsolutePath(Filename);
 
+  // When running under Windows, need to convert the path separators from
+  // `\` to `/`.
+  Guard = llvm::sys::path::convert_to_slash(Guard);
+
   // Sanitize the path. There are some rules for compatibility with the historic
   // style in include/llvm and include/clang which we want to preserve.
 
   // We don't want _INCLUDE_ in our guards.
   size_t PosInclude = Guard.rfind("include/");
   if (PosInclude != StringRef::npos)
     Guard = Guard.substr(PosInclude + std::strlen("include/"));
 

clang-tools-extra/unittests/clang-tidy/LLVMModuleTest.cpp

 #include "ClangTidyTest.h"
 #include "llvm/HeaderGuardCheck.h"
 #include "llvm/IncludeOrderCheck.h"
 #include "gtest/gtest.h"
 
 using namespace clang::tidy::llvm_check;
 
 namespace clang {
 namespace tidy {
 namespace test {
 
-// FIXME: It seems this might be incompatible to dos path. Investigating.
-#if !defined(_WIN32)
 static std::string runHeaderGuardCheck(StringRef Code, const Twine &Filename,
                                        Optional<StringRef> ExpectedWarning) {
   std::vector<ClangTidyError> Errors;
   std::string Result = test::runCheckOnCode<LLVMHeaderGuardCheck>(
       Code, &Errors, Filename, std::string("-xc++-header"));
   if (Errors.size() != (size_t)ExpectedWarning.hasValue())
     return "invalid error count";
   if (ExpectedWarning && *ExpectedWarning != Errors.back().Message.Message)
TEST(LLVMHeaderGuardCheckTest, FixHeaderGuards) {
   EXPECT_EQ("#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
             "#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
             "\n"
             "\n"
             "#endif\n",
             runHeaderGuardCheck(
                 "", "/llvm-project/clang-tools-extra/clangd/foo.h",
                 StringRef("header is missing header guard")));
-}
+
+#ifdef WIN32
+  // Check interaction with Windows-style path separators (\).
+  EXPECT_EQ(
+      "#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+      "#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+      "\n"
+      "\n"
+      "#endif\n",
+      runHeaderGuardCheck("", "llvm-project\\clang-tools-extra\\clangd\\foo.h",
+                          StringRef("header is missing header guard")));
+
+  EXPECT_EQ("#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+            "#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+            "\n"
+            "\n"
+            "#endif\n",
+            runHeaderGuardCheck(
+                "", "C:\\llvm-project\\clang-tools-extra\\clangd\\foo.h",
+                StringRef("header is missing header guard")));
+
+  EXPECT_EQ(
+      "#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+      "#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_FOO_H\n"
+      "\n"
+      "\n"
+      "#endif\n",
+      runHeaderGuardCheck(
+          "", "\\\\SambaShare\\llvm-project\\clang-tools-extra\\clangd\\foo.h",
+          StringRef("header is missing header guard")));
 #endif
+}
 
 } // namespace test
 } // namespace tidy
 } // namespace clang