Allow validator to be called from reads_json and writes_json

IPython/nbformat/current.py

@@ -28,13 +28,14 b' from IPython.nbformat.v3 import ('
     NotebookNode,
     new_code_cell, new_text_cell, new_notebook, new_output, new_worksheet,
     parse_filename, new_metadata, new_author, new_heading_cell, nbformat,
-    nbformat_minor, to_notebook_json
+    nbformat_minor, nbformat_schema, to_notebook_json
 )
 from IPython.nbformat import v3 as _v_latest
 
 from .reader import reads as reader_reads
 from .reader import versions
 from .convert import convert
+from .validator import nbvalidate
 
 #-----------------------------------------------------------------------------
 # Code
@@ -44,6 +45,7 b' current_nbformat = nbformat'
 current_nbformat_minor = nbformat_minor
 current_nbformat_module = _v_latest.__name__
 
+
 def docstring_nbformat_mod(func):
     """Decorator for docstrings referring to classes/functions accessed through
     nbformat.current.
@@ -76,11 +78,19 b' def parse_py(s, **kwargs):'
 
 def reads_json(s, **kwargs):
     """Read a JSON notebook from a string and return the NotebookNode object."""
-    return convert(reader_reads(s), current_nbformat)
+    nbjson = reader_reads(s)
+    num_errors = nbvalidate(nbjson)
+    if num_errors > 0:
+        print("Num errors: %d" % num_errors)
+    return convert(nbjson, current_nbformat)
 
 
 def writes_json(nb, **kwargs):
-    return versions[current_nbformat].writes_json(nb, **kwargs)
+    nbjson = versions[current_nbformat].writes_json(nb, **kwargs)
+    num_errors = nbvalidate(nbjson)
+    if num_errors > 0:
+        print("Num errors: %d" % num_errors)
+    return nbjson
 
 
 def reads_py(s, **kwargs):

IPython/nbformat/v3/__init__.py

@@ -19,7 +19,8 b' Authors:'
 from .nbbase import (
     NotebookNode,
     new_code_cell, new_text_cell, new_notebook, new_output, new_worksheet,
-    new_metadata, new_author, new_heading_cell, nbformat, nbformat_minor
+    new_metadata, new_author, new_heading_cell, nbformat, nbformat_minor,
+    nbformat_schema
 )
 
 from .nbjson import reads as reads_json, writes as writes_json

IPython/nbformat/v3/nbbase.py

@@ -11,6 +11,7 b' helpers to build the structs in the right form.'
 
 import pprint
 import uuid
+import os
 
 from IPython.utils.ipstruct import Struct
 from IPython.utils.py3compat import cast_unicode, unicode_type
@@ -22,6 +23,7 b' from IPython.utils.py3compat import cast_unicode, unicode_type'
 # Change this when incrementing the nbformat version
 nbformat = 3
 nbformat_minor = 0
+nbformat_schema = 'v3.withref.json'
 
 class NotebookNode(Struct):
     pass