don't insert name attributes into single part files (#2301)

Signed-off-by: Peter Hillman <peterh@wetafx.co.nz>
Co-authored-by: Cary Phillips <cary@ilm.com>

Author: peterhillman

src/wrappers/python/PyOpenEXR.cpp

@@ -1065,14 +1065,14 @@ PyFile::write(const char* outfilename)
 
         Header header;
 
-        if (P.name().empty() && parts.size() > 1)
+        if (!P.name().empty())
+            header.setName (P.name());
+	else if (parts.size() > 1)
         {
             std::stringstream n;
             n << "Part" << part_index;
             header.setName (n.str());
         }
-        else
-            header.setName (P.name());
 
         //
         // Add attributes from the py::dict to the output header

src/wrappers/python/tests/test_unittest.py

@@ -324,6 +324,8 @@ def test_write_half(self):
             # Verify reading it back gives the same data
             with OpenEXR.File(outfilename, separate_channels=True) as infile:
                 compare_files (infile, outfile)
+                if "name" in infile.header():
+                   raise Exception(f"name attribute was added to single part half file")
 
         os.remove(outfilename)