Allow exporters to be enabled or disabled via config

nbconvert/exporters/base.py

@@ -7,6 +7,7 @@
 
 import entrypoints
 
+from traitlets.config import get_config
 from traitlets.log import get_logger
 from traitlets.utils.importstring import import_item
 
@@ -32,6 +33,9 @@
 class ExporterNameError(NameError):
     pass
 
+class ExporterDisabledError(ValueError):
+    pass
+
 def export(exporter, nb, **kw):
     """
     Export a notebook object using specific exporter class.
@@ -85,26 +89,38 @@ def export(exporter, nb, **kw):
     return output, resources
 
 
-def get_exporter(name):
+def get_exporter(name, config=get_config()):
     """Given an exporter name or import path, return a class ready to be instantiated
 
-    Raises ValueError if exporter is not found
+    Raises ExporterName if exporter is not found or ExporterDisabledError if not enabled
     """
 
     if name == 'ipynb':
         name = 'notebook'
 
     try:
-        return entrypoints.get_single('nbconvert.exporters', name).load()
+        exporter = entrypoints.get_single('nbconvert.exporters', name).load()
+        if getattr(exporter(config=config), 'enabled', True):
+            return exporter
+        else:
+            raise ExporterDisabledError('Exporter "%s" disabled in configuration' % (name))
     except entrypoints.NoSuchEntryPoint:
         try:
-            return entrypoints.get_single('nbconvert.exporters', name.lower()).load()
+            exporter = entrypoints.get_single('nbconvert.exporters', name.lower()).load()
+            if getattr(exporter(config=config), 'enabled', True):
+                return exporter
+            else:
+                raise ExporterDisabledError('Exporter "%s" disabled in configuration' % (name))
         except entrypoints.NoSuchEntryPoint:
             pass
 
     if '.' in name:
         try:
-            return import_item(name)
+            exporter = import_item(name)
+            if getattr(exporter(config=config), 'enabled', True):
+                return exporter
+            else:
+                raise ExporterDisabledError('Exporter "%s" disabled in configuration' % (name))
         except ImportError:
             log = get_logger()
             log.error("Error importing %s" % name, exc_info=True)
@@ -113,10 +129,19 @@ def get_exporter(name):
                      % (name, ', '.join(get_export_names())))
 
 
-def get_export_names():
+def get_export_names(config=get_config()):
     """Return a list of the currently supported export targets
 
     Exporters can be found in external packages by registering
     them as an nbconvert.exporter entrypoint.
     """
-    return sorted(entrypoints.get_group_named('nbconvert.exporters'))
+    exporters = sorted(entrypoints.get_group_named('nbconvert.exporters'))
+    enabled_exporters = []
+    for exporter_name in exporters:
+        try:
+            e = get_exporter(exporter_name)(config=config)
+            if e.enabled:
+                enabled_exporters.append(exporter_name)
+        except ExporterDisabledError:
+            pass
+    return enabled_exporters

nbconvert/exporters/exporter.py

@@ -17,7 +17,7 @@
 
 from traitlets.config.configurable import LoggingConfigurable
 from traitlets.config import Config
-from traitlets import HasTraits, Unicode, List, TraitError
+from traitlets import Bool, HasTraits, Unicode, List, TraitError
 from traitlets.utils.importstring import import_item
 from ipython_genutils import text, py3compat
 
@@ -52,6 +52,10 @@ class Exporter(LoggingConfigurable):
     accompanying resources dict.
     """
 
+    enabled = Bool(True,
+        help = "Disable this exporter (and any exporters inherited from it)."
+    ).tag(config=True)
+
     file_extension = FilenameExtension(
         help="Extension of the file that should be written to disk"
     ).tag(config=True)

nbconvert/exporters/tests/test_export.py

@@ -10,9 +10,12 @@
 
 import nbformat
 import nbconvert.tests
+import pytest
+
+from traitlets.config import Config
 
 from .base import ExportersTestsBase
-from ..base import get_exporter, export, ExporterNameError, get_export_names
+from ..base import get_exporter, export, ExporterNameError, ExporterDisabledError, get_export_names
 from ..exporter import Exporter
 from ..python import PythonExporter
 
@@ -32,6 +35,15 @@ def test_export_wrong_name(self):
             pass
 
 
+    def test_export_disabled(self):
+        """
+        Trying to use a disabled exporter should raise ExporterDisbledError
+        """
+        config = Config({'NotebookExporter': {'enabled': False}})
+        with pytest.raises(ExporterDisabledError):
+            get_exporter('notebook', config=config)
+
+
     def test_export_filename(self):
         """
         Can a notebook be exported by filename?

nbconvert/exporters/tests/test_exporter.py

@@ -19,6 +19,7 @@
 from .base import ExportersTestsBase
 from ...preprocessors.base import Preprocessor
 from ..exporter import Exporter
+from ..base import get_export_names, ExporterDisabledError
 
 
 #-----------------------------------------------------------------------------
@@ -57,3 +58,18 @@ def test_preprocessor(self):
         exporter = Exporter(config=config)
         (notebook, resources) = exporter.from_filename(self._get_notebook())
         self.assertEqual(notebook['pizza'], 'cheese')
+
+    def test_get_export_names_disable(self):
+        """Can we disable a specific importer?"""
+        config = Config({'Exporter': {'enabled': False}})
+        export_names = get_export_names()
+        self.assertFalse('Exporter' in export_names)
+
+    def test_get_export_names_disable(self):
+        """Can we disable all exporters then enable a single one"""
+        config = Config({
+            'Exporter': {'enabled': False}, 
+            'NotebookExporter': {'enabled': True}
+        })
+        export_names = get_export_names(config=config)
+        self.assertEqual(export_names, ['notebook'])