1 files changed, 26 insertions, 13 deletions

diff --git a/nihil.posix/find_in_path.ccm b/nihil.posix/find_in_path.ccm
index 7bfa3b9..61df669 100644
--- a/nihil.posix/find_in_path.ccm
+++ b/nihil.posix/find_in_path.ccm
@@ -1,6 +1,7 @@
 // This source code is released into the public domain.
 module;
 
+#include <expected>
 #include <filesystem>
 #include <optional>
 #include <ranges>
@@ -16,27 +17,26 @@ import :getenv;
 
 namespace nihil {
 
-/*
- * Find an executable in $PATH and return the full path.  If $PATH is not set, uses _PATH_DEFPATH.
- * If the file can't be found or is not executable, returns std::nullopt.
- */
-export [[nodiscard]] auto
-find_in_path(std::filesystem::path const &file) -> std::optional<std::filesystem::path>
+// Find an executable by searching the given path string, which should be a colon-separated list of
+// directories, and return the full path.  If the file can't be found or is not executable, returns
+// an appropriate error.
+export [[nodiscard]] auto find_in_path(std::filesystem::path const &file, std::string_view path)
+	-> std::expected<std::filesystem::path, error>
 {
-	using namespace std::literals;
-
-	auto try_return = [](std::filesystem::path file) -> std::optional<std::filesystem::path> {
+	auto try_return =
+		[](std::filesystem::path file) -> std::expected<std::filesystem::path, error> {
 		auto ret = ::access(file.string().c_str(), X_OK);
 		if (ret == 0)
 			return {std::move(file)};
-		return {};
+		return std::unexpected(error(std::errc(errno)));
 	};
 
 	// Absolute pathname skips the search.
 	if (file.is_absolute())
 		return try_return(file);
 
-	auto const path = getenv("PATH").value_or(_PATH_DEFPATH); // NOLINT
+	// Default to ENOENT as the error.
+	auto err = error(std::errc::no_such_file_or_directory);
 
 	for (auto &&dir : path | std::views::split(':')) {
 		// An empty $PATH element means cwd.
@@ -44,10 +44,23 @@ find_in_path(std::filesystem::path const &file) -> std::optional<std::filesystem
 		                        : std::filesystem::path(std::string_view(dir));
 
 		if (auto ret = try_return(sdir / file); ret)
-			return {ret};
+			return ret;
+		// If we get an error other than ENOENT, cache it to return to the caller.
+		// This means we can propagate access() errors.
+		else if (ret.error().root_cause() != std::errc::no_such_file_or_directory)
+			err = std::move(ret.error());
 	}
 
-	return {};
+	return std::unexpected(std::move(err));
+}
+
+// Find an executable in $PATH and return the full path.  If $PATH is not set, uses _PATH_DEFPATH.
+// If the file can't be found or is not executable, returns an appropriate error.
+export [[nodiscard]] auto
+find_in_path(std::filesystem::path const &file) -> std::expected<std::filesystem::path, error>
+{
+	auto const path = getenv("PATH").value_or(_PATH_DEFPATH); // NOLINT
+	return find_in_path(file, path);
 }
 
 } // namespace nihil