Add function to create a temporary directory

Author: phst

elisp/private/tools/system.cc

@@ -1300,6 +1300,38 @@ absl::Status TemporaryFile::Write(const std::string_view contents) {
   return absl::OkStatus();
 }
 
+absl::StatusOr<FileName> CreateTemporaryDirectory() {
+#ifdef _WIN32
+  absl::Status status;
+  for (int i = 0; i < 10; i++) {
+    std::array<wchar_t, L_tmpnam + 1> buffer;
+    const wchar_t* absl_nullable name = _wtmpnam(buffer.data());
+    if (name == nullptr) {
+      return absl::UnavailableError("Cannot create temporary name");
+    }
+    absl::StatusOr<FileName> result = FileName::FromString(name);
+    if (!result.ok()) return result.status();
+    status = CreateDirectory(*result);
+    if (status.ok()) return *std::move(result);
+    LOG(ERROR) << status;
+  }
+  CHECK(!status.ok());
+  return status;
+#else
+  const char* const absl_nullable dir = std::getenv("TMPDIR");
+  std::string buffer = absl::StrCat(
+      dir == nullptr || *dir == '\0' ? "/tmp" : dir, "/elisp.XXXXXX");
+  char* const absl_nullable name = mkdtemp(Pointer(buffer));
+  if (name == nullptr) return ErrnoStatus("mkdtemp", buffer);
+  const absl::StatusOr<FileName> result = FileName::FromString(name);
+  if (!result.ok()) {
+    if (rmdir(name) != 0) LOG(ERROR) << ErrnoStatus("rmdir", name);
+    return result.status();
+  }
+  return *std::move(result);
+#endif
+}
+
 static void FlushEverything() {
   std::cout.flush();
   std::wcout.flush();

elisp/private/tools/system.h

@@ -378,6 +378,8 @@ class TemporaryFile final {
   std::FILE* absl_nullable file_;
 };
 
+absl::StatusOr<FileName> CreateTemporaryDirectory();
+
 struct RunOptions final {
   // If set, change to this directory in the subprocess.
   std::optional<FileName> directory;

tests/tools/system_test.cc

@@ -871,6 +871,19 @@ TEST(TemporaryFileTest, CreateWorks) {
   EXPECT_THAT(ReadFile(file->name()), IsOkAndHolds("Foo\n"));
 }
 
+TEST(CreateTemporaryDirectoryTest, Works) {
+  absl::StatusOr<FileName> dir = CreateTemporaryDirectory();
+  ASSERT_THAT(dir, IsOk());
+
+  const absl::Cleanup cleanup = [&dir] {
+    EXPECT_THAT(RemoveTree(*dir), IsOk());
+  };
+
+  FileName file = dir->Child(RULES_ELISP_NATIVE_LITERAL("file")).value();
+  EXPECT_THAT(WriteFile(file, "contents"), IsOk());
+  EXPECT_THAT(ReadFile(file), IsOkAndHolds("contents"));
+}
+
 [[maybe_unused]] static NativeString GetEnv(const NativeChar* const name) {
   const NativeChar* const absl_nullable value =
 #ifdef _WIN32