fix split_by_extenstion parse error extenstion

include/spdlog/details/file_helper.h

@@ -118,17 +118,18 @@ public:
     //
     // "my_folder/.mylog" => ("my_folder/.mylog")
     // "my_folder/.mylog.txt" => ("my_folder/.mylog", ".txt")
-
     static std::tuple<filename_t, filename_t> split_by_extenstion(const filename_t& fname)
     {
         auto index = fname.rfind('.');
-        bool found_ext = index != filename_t::npos && index !=0 && fname[index - 1] != details::os::folder_sep;
-        if (found_ext)
+        if (index != filename_t::npos && index != fname.size() - 1 &&index !=0 && fname[index - 1] != details::os::folder_sep) 
+        {
+            auto index2 = fname.find(details::os::folder_sep, index);
+            if (index2 == fname.npos) {
                  return std::make_tuple(fname.substr(0, index), fname.substr(index));
-        else
-            return std::make_tuple(fname, filename_t());
             }
-
+        }
+        return std::make_tuple(fname, std::string());
+    }
 private:
     FILE* _fd;
     filename_t _filename;

tests/file_helper.cpp

@@ -145,5 +145,19 @@ TEST_CASE("file_helper_split_by_extenstion7", "[file_helper::split_by_extenstion
 }
 
 
+TEST_CASE("file_helper_split_by_extenstion8", "[file_helper::split_by_extenstion(hidden_file)]]")
+{
+#ifdef _WIN32
+    auto filename = "folder.ext\\mylog";
+    auto expected_basename = "folder.ext\\mylog";
+#else
+    auto filename = "folder.ext/mylog";
+    auto expected_basename = "folder.ext/mylog";
+#endif
+    std::string basename, ext;
+    std::tie(basename, ext) = file_helper::split_by_extenstion(filename);
+    REQUIRE(basename == expected_basename);
+    REQUIRE(ext == "");
+}