From c1c317014002311874006f319b04121c88ef4672 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Fri, 5 Jun 2026 09:05:03 +0200
Subject: magic: improve error handling

---
 cabinet/magic.cpp | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

(limited to 'cabinet/magic.cpp')

diff --git a/cabinet/magic.cpp b/cabinet/magic.cpp
index 08b3046..96b78a3 100644
--- a/cabinet/magic.cpp
+++ b/cabinet/magic.cpp
@@ -53,24 +53,35 @@ namespace cab
     return *this;
   }
 
-  auto magic::process(std::filesystem::path path) -> std::expected<std::string, std::string>
+  auto magic::process(std::filesystem::path path) -> std::expected<std::string, std::error_code>
   {
-    auto result = ::magic_file(m_cookie, path.native().c_str());
-    if (!result)
+    return handle_result(::magic_file(m_cookie, path.native().c_str()));
+  }
+
+  auto magic::process(int file_descriptor) -> std::expected<std::string, std::error_code>
+  {
+    if (file_descriptor < 0)
     {
-      return std::unexpected{std::string{::magic_error(m_cookie)}};
+      return std::unexpected{std::make_error_code(std::errc::invalid_argument)};
     }
-    return result;
+
+    return handle_result(::magic_descriptor(m_cookie, file_descriptor));
   }
 
-  auto magic::process(int file_descriptor) -> std::expected<std::string, std::string>
+  auto magic::handle_result(char const * result) -> std::expected<std::string, std::error_code>
   {
-    auto result = ::magic_descriptor(m_cookie, file_descriptor);
+    auto errno_copy = errno;
+
     if (!result)
     {
-      return std::unexpected{std::string{::magic_error(m_cookie)}};
+      auto magic_errno = ::magic_errno(m_cookie);
+      if (!magic_errno && !errno)
+      {
+        return std::unexpected{std::make_error_code(std::errc::invalid_argument)};
+      }
     }
-    return result;
+
+    return std::string{result};
   }
 
   auto swap(magic & lhs, magic & rhs) noexcept -> void
-- 
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