From 49fb44c299ff16c114858f9ec4c254806dadef04 Mon Sep 17 00:00:00 2001
From: Alexis Jeandet <alexis.jeandet@member.fsf.org>
Date: Wed, 18 Feb 2026 10:16:09 +0100
Subject: [PATCH] Do not allow anymore to create Variables or Attributes with
 an empty name.

While technically legal (no mention in the official format doc), others CDF implementations consider the file corrupted if a name is empty.

Fixes #48
---
 include/cdfpp/attribute.hpp              |  8 ++++++++
 include/cdfpp/cdf-file.hpp               |  2 ++
 include/cdfpp/variable.hpp               |  8 ++++++++
 tests/python_variable_set_values/test.py | 14 ++++++++++++++
 4 files changed, 32 insertions(+)

diff --git a/include/cdfpp/attribute.hpp b/include/cdfpp/attribute.hpp
index 5d0dcc2..97be0d6 100644
--- a/include/cdfpp/attribute.hpp
+++ b/include/cdfpp/attribute.hpp
@@ -56,6 +56,10 @@ struct Attribute
     Attribute& operator=(const Attribute&) = default;
     Attribute(const std::string& name, attr_data_t&& data) : name { name }
     {
+        if (name.empty())
+        {
+            throw std::invalid_argument { "Attribute name cannot be empty" };
+        }
         this->data = std::move(data);
     }
 
@@ -177,6 +181,10 @@ struct VariableAttribute
     VariableAttribute& operator=(const VariableAttribute&) = default;
     VariableAttribute(const std::string& name, attr_data_t&& data) : name { name }
     {
+        if (name.empty())
+        {
+            throw std::invalid_argument { "Attribute name cannot be empty" };
+        }
         this->data = std::move(data);
     }
 
diff --git a/include/cdfpp/cdf-file.hpp b/include/cdfpp/cdf-file.hpp
index 4de9547..56bdb44 100644
--- a/include/cdfpp/cdf-file.hpp
+++ b/include/cdfpp/cdf-file.hpp
@@ -36,6 +36,8 @@
 template <class stream_t>
 inline stream_t& operator<<(stream_t& os, const cdf_map<std::string, cdf::Variable>& variables)
 {
+    std::for_each(std::cbegin(variables), std::cend(variables),
+        [&os](const auto& item) { item.second.__repr__(os, indent_t {}, false); });
     return os;
 }
 
diff --git a/include/cdfpp/variable.hpp b/include/cdfpp/variable.hpp
index 74c9ac1..a497b0a 100644
--- a/include/cdfpp/variable.hpp
+++ b/include/cdfpp/variable.hpp
@@ -102,6 +102,10 @@ struct Variable
             , p_is_nrv { is_nrv }
             , p_compression { compression_type }
     {
+        if (name.empty())
+        {
+            throw std::invalid_argument { "Variable name cannot be empty" };
+        }
         if (this->majority() == cdf_majority::column)
         {
             majority::swap(_data(), p_shape);
@@ -120,6 +124,10 @@ struct Variable
             , p_is_nrv { is_nrv }
             , p_compression { compression_type }
     {
+        if (name.empty())
+        {
+            throw std::invalid_argument { "Variable name cannot be empty" };
+        }
     }
 
     inline bool operator==(const Variable& other) const
diff --git a/tests/python_variable_set_values/test.py b/tests/python_variable_set_values/test.py
index 7727d23..314bf11 100755
--- a/tests/python_variable_set_values/test.py
+++ b/tests/python_variable_set_values/test.py
@@ -263,6 +263,20 @@ def test_filter_cdf_with_regex(self):
         self.assertIn("global_attr2", self.cdf.attributes)
         self.assertIn("global_attr3", self.cdf.attributes)
 
+class PycdfEmptyNamesAreNotAllowed(unittest.TestCase):
+    def test_variable_name_cannot_be_empty(self):
+        cdf = pycdfpp.CDF()
+        with self.assertRaises(ValueError):
+            cdf.add_variable("", values=np.arange(10))
+
+    def test_attribute_name_cannot_be_empty(self):
+        cdf = pycdfpp.CDF()
+        cdf.add_variable("var1", values=np.arange(10))
+        with self.assertRaises(ValueError):
+            cdf["var1"].add_attribute("", "value")
+        with self.assertRaises(ValueError):
+            cdf.add_attribute("", ["value"])
+
 
 if __name__ == '__main__':
     unittest.main()