nbconvert --to script dispatches to custom nbconvert exporter in metadata

IPython/nbconvert/exporters/script.py

@@ -1,14 +1,33 b''
 """Generic script exporter class for any kernel language"""
 
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
+
 from .templateexporter import TemplateExporter
 
+from IPython.utils.traitlets import Dict
+
 class ScriptExporter(TemplateExporter):
+    
+    _exporters = Dict()
+    
     def _template_file_default(self):
         return 'script'
 
     def from_notebook_node(self, nb, resources=None, **kw):
         langinfo = nb.metadata.get('language_info', {})
+        
+        # delegate to custom exporter, if specified
+        exporter_name = langinfo.get('nbconvert_exporter')
+        if exporter_name and exporter_name != 'script':
+            self.log.debug("Loading script exporter: %s", exporter_name)
+            from .export import exporter_map
+            if exporter_name not in self._exporters:
+                Exporter = exporter_map[exporter_name]
+                self._exporters[exporter_name] = Exporter(parent=self)
+            exporter = self._exporters[exporter_name]
+            return exporter.from_notebook_node(nb, resources, **kw)
+        
         self.file_extension = langinfo.get('file_extension', '.txt')
         self.output_mimetype = langinfo.get('mimetype', 'text/plain')
-
         return super(ScriptExporter, self).from_notebook_node(nb, resources, **kw)