Make ClearMetadataPreprocessor work for cells of any type, and some related improvements

nbconvert/nbconvertapp.py

@@ -118,6 +118,18 @@ def validate(self, obj, value):
             """Clear output of current file and save in place,
         overwriting the existing notebook. """,
         ),
+        "clear-metadata": (
+            {
+                "NbConvertApp": {
+                    "use_output_suffix": False,
+                    "export_format": "notebook",
+                },
+                "FilesWriter": {"build_directory": ""},
+                "ClearMetadataPreprocessor": {"enabled": True},
+            },
+            """Clear metadata of current file and save in place,
+        overwriting the existing notebook. """,
+        ),
         "coalesce-streams": (
             {
                 "NbConvertApp": {"use_output_suffix": False, "export_format": "notebook"},

nbconvert/preprocessors/clearmetadata.py

@@ -1,4 +1,4 @@
-"""Module containing a preprocessor that removes metadata from code cells"""
+"""Module containing a preprocessor that removes notebook or cell metadata"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
@@ -10,7 +10,7 @@
 
 class ClearMetadataPreprocessor(Preprocessor):
     """
-    Removes all the metadata from all code cells in a notebook.
+    Removes global or cell-level metadata from a notebook.
     """
 
     clear_cell_metadata = Bool(
@@ -24,16 +24,16 @@ class ClearMetadataPreprocessor(Preprocessor):
     preserve_nb_metadata_mask = Set(
         [("language_info", "name")],
         help=(
-            "Indicates the key paths to preserve when deleting metadata "
-            "across both cells and notebook metadata fields. Tuples of "
-            "keys can be passed to preserved specific nested values"
+            "Indicates the key paths to preserve when deleting notebook "
+            "metadata fields. Tuples of keys can be passed to preserve "
+            "specific nested values."
         ),
     ).tag(config=True)
     preserve_cell_metadata_mask = Set(
         help=(
             "Indicates the key paths to preserve when deleting metadata "
-            "across both cells and notebook metadata fields. Tuples of "
-            "keys can be passed to preserved specific nested values"
+            "across all cells in a notebook. Tuples of keys can be passed "
+            "to preserve specific nested values."
         )
     ).tag(config=True)
 
@@ -73,14 +73,13 @@ def nested_filter(self, items, mask):
 
     def preprocess_cell(self, cell, resources, cell_index):
         """
-        All the code cells are returned with an empty metadata field.
+        All the cells are returned with a trimmed down metadata field.
         """
-        if self.clear_cell_metadata and cell.cell_type == "code":  # noqa: SIM102
+        if self.clear_cell_metadata and "metadata" in cell:
             # Remove metadata
-            if "metadata" in cell:
-                cell.metadata = dict(
-                    self.nested_filter(cell.metadata.items(), self.preserve_cell_metadata_mask)
-                )
+            cell.metadata = dict(
+                self.nested_filter(cell.metadata.items(), self.preserve_cell_metadata_mask)
+            )
         return cell, resources
 
     def preprocess(self, nb, resources):