Add option to validate templates using jinja2schema

Use jinja2schema to validate templates when --validate-templates
is passed in.

Closes thanethomson#99

statik/cmdline.py

@@ -160,6 +160,12 @@ def main():
         help='Display version info for Statik',
         action='store_true',
     )
+
+    group_info.add_argument(
+        '--validate-templates',
+        help='Validate that variables used in jinja templates are actually available to be used.',
+        action='store_true',
+    )
     args = parser.parse_args()
 
     error_context = StatikErrorContext()
@@ -215,7 +221,8 @@ def main():
                 output_path=output_path,
                 in_memory=False,
                 safe_mode=args.safe_mode,
-                error_context=error_context
+                error_context=error_context,
+                validate_templates=args.validate_templates
             )
 
         if args.upload and args.upload == 'SFTP':

statik/generator.py

@@ -8,8 +8,8 @@
 ]
 
 
-def generate(input_path, output_path=None, in_memory=False, safe_mode=False, error_context=None):
+def generate(input_path, output_path=None, in_memory=False, safe_mode=False, error_context=None, validate_templates=False):
     """Executes the Statik site generator using the given parameters.
     """
-    project = StatikProject(input_path, safe_mode=safe_mode, error_context=error_context)
+    project = StatikProject(input_path, validate_templates=validate_templates, safe_mode=safe_mode, error_context=error_context)
     return project.generate(output_path=output_path, in_memory=in_memory)

statik/project.py

@@ -47,6 +47,7 @@ def __init__(self, path, **kwargs):
         """
         self.error_context = kwargs.pop('error_context', None)
         self.error_context = self.error_context or StatikErrorContext()
+        self.validate_templates = kwargs.pop('validate_templates', False)
 
         if 'config' in kwargs and isinstance(kwargs['config'], dict):
             logger.debug("Loading project configuration from constructor arguments")
@@ -248,7 +249,8 @@ def process_views(self):
                     view.process(
                         self.db,
                         safe_mode=self.safe_mode,
-                        extra_context=self.project_context
+                        extra_context=self.project_context,
+                        validate_templates=self.validate_templates
                     )
                 )
             except StatikError as exc:

statik/utils.py

@@ -9,8 +9,10 @@
 import stat
 from copy import deepcopy, copy
 import shutil
+import re
 
 import six
+from jinja2schema import to_json_schema, infer
 
 if six.PY3:
     import importlib.util
@@ -44,6 +46,7 @@
     'find_first_file_with_ext',
     'uncapitalize',
     'find_duplicates_in_array',
+    'validate_jinja_template',
 ]
 
 DEFAULT_CONFIG_CONTENT = """project-name: Your project name
@@ -382,3 +385,27 @@ def find_duplicates_in_array(array):
                 duplicates.append(item)
 
     return duplicates
+
+
+def validate_jinja_template(template, ctx):
+    """Checks that variables used in templates are actually available to be used in context.
+    Logs a warning if a variable used in the template is not found in the context.
+
+    Args:
+        template: Path to the template to check
+        ctx: dictionary of the variables in context
+    """
+    tag_re = re.compile(r'(<!--.*?-->|<[^>]*>)')
+    with open(template) as file:
+        stripped_template = tag_re.sub('', file.read())
+        try:
+            result = to_json_schema(infer(stripped_template))
+            for item in result['required']:
+                if item not in list(ctx.keys()):
+                    logger.warning("'%s' was used in a template, "
+                                   "but it's not available to be used. Template: %s"
+                                   % (item, template))
+        except Exception as e:
+            logger.warning(
+                "Template validation failed (likely an issue with jinja2schema): %s: %s",
+                template, e)

statik/views.py

@@ -10,6 +10,7 @@
 from statik.errors import *
 from statik.utils import *
 from statik.context import StatikContext
+from statik.utils import validate_jinja_template
 
 import logging
 
@@ -248,9 +249,12 @@ def __repr__(self):
     def __str__(self):
         return repr(self)
 
-    def render(self, context, db=None, safe_mode=False, extra_context=None):
+    def render(self, context, db=None, safe_mode=False, extra_context=None, validate_templates=False):
         ctx = context.build(db=db, safe_mode=safe_mode, extra=extra_context)
         logger.debug("Rendering view %s with context: %s", self.view_name, ctx)
+        if validate_templates:
+            validate_jinja_template(self.template.filename, ctx)
+
         return dict_from_path(
             self.path.render(),
             final_value=self.template.render(ctx)
@@ -279,7 +283,7 @@ def __repr__(self):
     def __str__(self):
         return repr(self)
 
-    def render(self, context, db=None, safe_mode=False, extra_context=None):
+    def render(self, context, db=None, safe_mode=False, extra_context=None, validate_templates=False):
         """Renders the given context using the specified database, returning a dictionary
         containing path segments and rendered view contents."""
         if not db:
@@ -302,6 +306,8 @@ def render(self, context, db=None, safe_mode=False, extra_context=None):
                 extra=extra_ctx
             )
             inst_path = self.path.render(inst=inst, context=ctx)
+            if validate_templates:
+                validate_jinja_template(self.template.filename, ctx)
             rendered_view = self.template.render(ctx)
             rendered_views = deep_merge_dict(
                 rendered_views,
@@ -387,13 +393,14 @@ def __repr__(self):
     def __str__(self):
         return repr(self)
 
-    def process(self, db, safe_mode=False, extra_context=None):
+    def process(self, db, safe_mode=False, extra_context=None, validate_templates=False):
         """Deprecated. Rather use StatikView.render()."""
         return self.renderer.render(
             self.context,
             db,
             safe_mode=safe_mode,
-            extra_context=extra_context
+            extra_context=extra_context,
+            validate_templates=validate_templates
         )
 
     def render(self, db, safe_mode=False, extra_context=None):

tests/modular/test_utils.py

@@ -7,7 +7,6 @@
 
 from statik.utils import *
 
-
 TEST_XML = """
 <div class="something">
     Hello world!
@@ -85,6 +84,15 @@ def test_get_url_file_ext(self):
             ''
         )
 
+    def test_validate_jinja_template(self):
+        from mock import patch, mock_open
+        with patch("statik.utils.logger.warning") as mock_logger:
+            with patch("statik.utils.open", mock_open(read_data="{{ baz }}")):
+                validate_jinja_template('/path/to/somewhere', {'posts': 'foo'})
+                mock_logger.assert_called_with("'baz' was used in a template, "
+                                               "but it's not available to be used. "
+                                               "Template: /path/to/somewhere")
+
 
 if __name__ == "__main__":
     unittest.main()