feat: Scoped slots + Updated docs (#495)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/django_components/expression.py

@@ -0,0 +1,46 @@
+from typing import Any, Dict, List, Mapping, Optional, Union
+
+from django.template import Context
+from django.template.base import FilterExpression, Parser
+
+
+def resolve_expression_as_identifier(
+    context: Context,
+    fexp: FilterExpression,
+) -> str:
+    resolved = fexp.resolve(context)
+    if not isinstance(resolved, str):
+        raise ValueError(
+            f"FilterExpression '{fexp}' was expected to resolve to string, instead got '{type(resolved)}'"
+        )
+    if not resolved.isidentifier():
+        raise ValueError(
+            f"FilterExpression '{fexp}' was expected to resolve to valid identifier, instead got '{resolved}'"
+        )
+    return resolved
+
+
+def safe_resolve_list(args: List[FilterExpression], context: Context) -> List:
+    return [safe_resolve(arg, context) for arg in args]
+
+
+def safe_resolve_dict(
+    kwargs: Union[Mapping[str, FilterExpression], Dict[str, FilterExpression]],
+    context: Context,
+) -> Dict:
+    return {key: safe_resolve(kwarg, context) for key, kwarg in kwargs.items()}
+
+
+def safe_resolve(context_item: FilterExpression, context: Context) -> Any:
+    """Resolve FilterExpressions and Variables in context if possible. Return other items unchanged."""
+    return context_item.resolve(context) if hasattr(context_item, "resolve") else context_item
+
+
+def resolve_string(
+    s: str,
+    parser: Optional[Parser] = None,
+    context: Optional[Mapping[str, Any]] = None,
+) -> str:
+    parser = parser or Parser([])
+    context = context or {}
+    return parser.compile_filter(s).resolve(context)