PR: Use fastjsonschema if installed and add tests

.github/workflows/tests.yml

@@ -22,7 +22,7 @@ jobs:
     - name: Install test dependencies
       run: |
         pip install --upgrade pip setuptools
-        pip install nbformat[test]
+        pip install .[test]
         pip install codecov
     - name: Install nbformat
       run: |

README.md

@@ -2,8 +2,7 @@
 
 [![codecov.io](https://codecov.io/github/jupyter/nbformat/coverage.svg?branch=master)](https://codecov.io/github/jupyter/nbformat?branch=master)
 [![Code Health](https://landscape.io/github/jupyter/nbformat/master/landscape.svg?style=flat)](https://landscape.io/github/jupyter/nbformat/master)
-
-
+![CI Tests](https://github.com/jupyter/nbformat/workflows/Run%20tests/badge.svg)
 
 `nbformat` contains the reference implementation of the [Jupyter Notebook format][],
 and Python APIs for working with notebooks.
@@ -20,6 +19,16 @@ From the command line:
 pip install nbformat
 ```
 
+## Using a different json schema validator
+
+You can install and use [fastjsonschema](https://horejsek.github.io/python-fastjsonschema/) by running:
+
+``` {.sourceCode .bash}
+pip install nbformat[fast]
+```
+
+To enable fast validation with `fastjsonschema`, set the environment variable `NBFORMAT_VALIDATOR` to the value `fastjsonschema`.
+
 ## Python Version Support
 
 This library supported python 2.7 and python 3.5+ for `4.x.x` releases. With python 2's end-of-life nbformat `5.x.x` is now python 3.5+ only. Support for 3.5 will be dropped when it's officially sunset by the python organization.

docs/api.rst

@@ -120,3 +120,15 @@ bindings are available, and an in-memory store otherwise.
 .. autoclass:: SQLiteSignatureStore
 
 .. autoclass:: MemorySignatureStore
+
+Optional fast validation
+------------------------
+
+You can install and use `fastjsonschema <https://horejsek.github.io/python-fastjsonschema/>`_ by running::
+
+    pip install nbformat[fast]
+
+
+To enable fast validation with `fastjsonschema`, set the environment variable::
+
+   NBFORMAT_VALIDATOR="fastjsonschema"

docs/changelog.rst

@@ -7,6 +7,10 @@ Changes in nbformat
 In Development
 ==============
 
+- Add optional support for using `fastjsonschema` as the JSON validation library.
+  To enable fast validation, install `fastjsonschema` and set the environment
+  variable `NBFORMAT_VALIDATOR` to the value `fastjsonschema`.
+
 5.0.7
 =====
 

nbformat/json_compat.py

@@ -0,0 +1,82 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+"""
+Common validator wrapper to provide a uniform usage of other schema validation
+libraries.
+"""
+
+import os
+
+import jsonschema
+from jsonschema import Draft4Validator as _JsonSchemaValidator
+from jsonschema import ValidationError
+
+try:
+    import fastjsonschema
+    from fastjsonschema import JsonSchemaException as _JsonSchemaException
+except ImportError:
+    fastjsonschema = None
+    _JsonSchemaException = ValidationError
+
+
+class JsonSchemaValidator:
+    name = "jsonschema"
+
+    def __init__(self, schema):
+        self._schema = schema
+        self._default_validator = _JsonSchemaValidator(schema)  # Default
+        self._validator = self._default_validator
+
+    def validate(self, data):
+        self._default_validator.validate(data)
+
+    def iter_errors(self, data, schema=None):
+        return self._default_validator.iter_errors(data, schema)
+
+
+class FastJsonSchemaValidator(JsonSchemaValidator):
+    name = "fastjsonschema"
+
+    def __init__(self, schema):
+        self._validator = fastjsonschema.compile(schema)
+
+    def validate(self, data):
+        try:
+            self._validator(data)
+        except _JsonSchemaException as error:
+            raise ValidationError(error.message, schema_path=error.path)
+
+    def iter_errors(self, data, schema=None):
+        errors = []
+        validate_func = self._validator if schema is None else fastjsonschema.compile(schema)
+        try:
+            validate_func(data)
+        except _JsonSchemaException as error:
+            errors = [ValidationError(error.message, schema_path=error.path)]
+
+        return errors
+
+
+_VALIDATOR_MAP = [
+    ("fastjsonschema", fastjsonschema, FastJsonSchemaValidator),
+    ("jsonschema", jsonschema, JsonSchemaValidator),
+]
+VALIDATORS = [item[0] for item in _VALIDATOR_MAP]
+
+
+def _validator_for_name(validator_name):
+    if validator_name not in VALIDATORS:
+        raise ValueError("Invalid validator '{0}' value!\nValid values are: {1}".format(
+            validator_name, VALIDATORS))
+
+    for (name, module, validator_cls) in _VALIDATOR_MAP:
+        if module and validator_name == name:
+            return validator_cls
+
+
+def get_current_validator():
+    """
+    Return the default validator based on the value of an environment variable.
+    """
+    validator_name = os.environ.get("NBFORMAT_VALIDATOR", "jsonschema")
+    return _validator_for_name(validator_name)

nbformat/tests/base.py

@@ -12,9 +12,10 @@
 class TestsBase(unittest.TestCase):
     """Base tests class."""
 
-    def fopen(self, f, mode=u'r',encoding='utf-8'):
-        return io.open(os.path.join(self._get_files_path(), f), mode, encoding=encoding)
+    @classmethod
+    def fopen(cls, f, mode=u'r',encoding='utf-8'):
+        return io.open(os.path.join(cls._get_files_path(), f), mode, encoding=encoding)
 
-
-    def _get_files_path(self):
+    @classmethod
+    def _get_files_path(cls):
         return os.path.dirname(__file__)

nbformat/tests/many_tracebacks.ipynb

@@ -0,0 +1,46 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "NameError",
+     "evalue": "name 'iAmNotDefined' is not defined",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-22-56e1109ae320>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0miAmNotDefined\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mNameError\u001b[0m: name 'iAmNotDefined' is not defined"
+     ]
+    }
+   ],
+   "source": [
+    "# Imagine this cell called a function which runs things on a cluster and you have an error"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.8.5"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}