policies/expression: migrate to raw python instead of jinja2 (#49)

* policies/expression: migrate to raw python instead of jinja2

* lib/expression: create base evaluator, custom subclass for policies

* core: rewrite propertymappings to use python

* providers/saml: update to new PropertyMappings

* sources/ldap: update to new PropertyMappings

* docs: update docs for new propertymappings

* root: remove jinja2

* root: re-add jinja to lock file as its implicitly required

passbook/core/models.py

@@ -5,14 +5,11 @@ from uuid import uuid4
 
 from django.contrib.auth.models import AbstractUser
 from django.contrib.postgres.fields import JSONField
-from django.core.exceptions import ValidationError
 from django.db import models
 from django.http import HttpRequest
 from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
 from guardian.mixins import GuardianUserMixin
-from jinja2 import Undefined
-from jinja2.exceptions import TemplateSyntaxError, UndefinedError
 from model_utils.managers import InheritanceManager
 from structlog import get_logger
 
@@ -206,30 +203,14 @@ class PropertyMapping(models.Model):
         self, user: Optional[User], request: Optional[HttpRequest], **kwargs
     ) -> Any:
         """Evaluate `self.expression` using `**kwargs` as Context."""
-        from passbook.policies.expression.evaluator import Evaluator
+        from passbook.core.expression import PropertyMappingEvaluator
 
-        evaluator = Evaluator()
+        evaluator = PropertyMappingEvaluator()
+        evaluator.set_context(user, request, **kwargs)
         try:
-            expression = evaluator.env.from_string(self.expression)
-        except TemplateSyntaxError as exc:
+            return evaluator.evaluate(self.expression)
+        except (ValueError, SyntaxError) as exc:
             raise PropertyMappingExpressionException from exc
-        try:
-            response = expression.render(user=user, request=request, **kwargs)
-            if isinstance(response, Undefined):
-                raise PropertyMappingExpressionException("Response was 'Undefined'")
-            return response
-        except UndefinedError as exc:
-            raise PropertyMappingExpressionException from exc
-
-    def save(self, *args, **kwargs):
-        from passbook.policies.expression.evaluator import Evaluator
-
-        evaluator = Evaluator()
-        try:
-            evaluator.env.from_string(self.expression)
-        except TemplateSyntaxError as exc:
-            raise ValidationError("Expression Syntax Error") from exc
-        return super().save(*args, **kwargs)
 
     def __str__(self):
         return f"Property Mapping {self.name}"