Consolidated file validation

pre_commit/clientlib/validate_base.py

@@ -0,0 +1,51 @@
+
+import jsonschema
+import jsonschema.exceptions
+import os.path
+import yaml
+
+from pre_commit import git
+
+
+def get_validator(
+    default_filename,
+    json_schema,
+    exception_type,
+    additional_validation_strategy=lambda obj: None,
+):
+    """Returns a function which will validate a yaml file for correctness
+
+    Args:
+        default_filename - Default filename to look for if none is specified
+        json_schema - JSON schema to validate file with
+        exception_type - Error type to raise on failure
+        additional_validation_strategy - Strategy for additional validation of
+            the object read from the file.  The function should either raise
+            exception_type on failure.
+    """
+
+    def validate(filename=None):
+        filename = filename or os.path.join(git.get_root(), default_filename)
+
+        if not os.path.exists(filename):
+            raise exception_type('File {0} does not exist'.format(filename))
+
+        file_contents = open(filename, 'r').read()
+
+        try:
+            obj = yaml.load(file_contents)
+        except Exception as e:
+            raise exception_type(
+                'File {0} is not a valid yaml file'.format(filename), e,
+            )
+
+        try:
+            jsonschema.validate(obj, json_schema)
+        except jsonschema.exceptions.ValidationError as e:
+            raise exception_type(
+                'File {0} is not a valid file'.format(filename), e,
+            )
+
+        additional_validation_strategy(obj)
+
+    return validate