Split classes and add reading the current validator from environment …

…variable

.travis.yml

@@ -16,8 +16,6 @@ install:
     - pip freeze
 script:
     - py.test -v --cov nbformat nbformat
-    - pip uninstall fastjsonschema --yes
-    - py.test -v --cov nbformat nbformat
 after_success:
     - codecov
 matrix:

appveyor.yml

@@ -23,8 +23,6 @@ build: off
 # to run your custom scripts instead of automatic tests
 test_script:
   - 'py.test -v --cov nbformat nbformat'
-  - 'pip uninstall fastjsonschema --yes'
-  - 'py.test -v --cov nbformat nbformat'
 
 on_success:
   - codecov

nbformat/json_compat.py

@@ -5,6 +5,9 @@
 libraries.
 """
 
+import os
+
+import jsonschema
 from jsonschema import Draft4Validator as _JsonSchemaValidator
 from jsonschema import ValidationError
 
@@ -16,32 +19,56 @@
     _JsonSchemaException = ValidationError
 
 
-class Validator:
-    """
-    Common validator wrapper to provide a uniform usage of other schema validation
-    libraries.
-    """
+class JsonSchemaValidator:
+    name = "jsonschema"
 
     def __init__(self, schema):
         self._schema = schema
-
-        # Validation libraries
-        self._jsonschema = _JsonSchemaValidator(schema)  # Default
-        self._fastjsonschema_validate = fastjsonschema.compile(schema) if fastjsonschema else None
+        self._default_validator = _JsonSchemaValidator(schema)  # Default
+        self._validator = self._default_validator
 
     def validate(self, data):
-        """
-        Validate the schema of ``data``.
-
-        Will use ``fastjsonschema`` if available.
-        """
-        if fastjsonschema:
-            try:
-                self._fastjsonschema_validate(data)
-            except _JsonSchemaException as e:
-                raise ValidationError(e.message)
-        else:
-            self._jsonschema.validate(data)
+        self._default_validator.validate(data)
 
     def iter_errors(self, data, schema=None):
-        return self._jsonschema.iter_errors(data, schema)
+        return self._default_validator.iter_errors(data, schema)
+
+
+class FastJsonSchemaValidator(JsonSchemaValidator):
+    name = "fastjsonschema"
+
+    def __init__(self, schema):
+        super().__init__(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)
+
+
+_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 current 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__)