refactor: move kwargs resolution to render-time + cleanup (#594)

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

README.md

@@ -537,7 +537,7 @@ Component.render(
     context: Mapping | django.template.Context | None = None,
     args: List[Any] | None = None,
     kwargs: Dict[str, Any] | None = None,
-    slots: Dict[str, str | SafeString | SlotRenderFunc] | None = None,
+    slots: Dict[str, str | SafeString | SlotFunc] | None = None,
     escape_slots_content: bool = True
 ) -> str:
 ```
@@ -550,7 +550,7 @@ Component.render(
 
 - _`slots`_ - Component slot fills. This is the same as pasing `{% fill %}` tags to the component.
   Accepts a dictionary of `{ slot_name: slot_content }` where `slot_content` can be a string
-  or [`SlotRenderFunc`](#slotrenderfunc).
+  or [`SlotFunc`](#slotfunc).
 
 - _`escape_slots_content`_ - Whether the content from `slots` should be escaped. `True` by default to prevent XSS attacks. If you disable escaping, you should make sure that any content you pass to the slots is safe, especially if it comes from user input.
 
@@ -559,7 +559,7 @@ Component.render(
   - NOTE: In "isolated" mode, context is NOT accessible, and data MUST be passed via
     component's args and kwargs.
 
-#### `SlotRenderFunc`
+#### `SlotFunc`
 
 When rendering components with slots in `render` or `render_to_response`, you can pass either a string or a function.
 
@@ -602,24 +602,30 @@ that allow you to specify the types of args, kwargs, slots, and
 data.
 
 ```py
-from typing import NotRequired, Tuple, TypedDict
+from typing import NotRequired, Tuple, TypedDict, SlotFunc
 
-# Tuple
+# Positional inputs - Tuple
 Args = Tuple[int, str]
 
-# Mapping
+# Kwargs inputs - Mapping
 class Kwargs(TypedDict):
     variable: str
     another: int
     maybe_var: NotRequired[int]
 
-# Mapping
+# Data returned from `get_context_data` - Mapping
 class Data(TypedDict):
     variable: str
 
-# Mapping
+# The data available to the `my_slot` scoped slot
+class MySlotData(TypedDict):
+    value: int
+
+# Slot functions - Mapping
 class Slots(TypedDict):
-    my_slot: NotRequired[str]
+    # Use SlotFunc for slot functions.
+    # The generic specifies the `data` dictionary
+    my_slot: NotRequired[SlotFunc[MySlotData]]
 
 class Button(Component[Args, Kwargs, Data, Slots]):
     def get_context_data(self, variable, another):

src/django_components/__init__.py

@@ -19,6 +19,10 @@ from django_components.component_registry import (
     registry as registry,
 )
 from django_components.library import TagProtectedError as TagProtectedError
+from django_components.slots import (
+    SlotContent as SlotContent,
+    SlotFunc as SlotFunc,
+)
 from django_components.tag_formatter import (
     ComponentFormatter as ComponentFormatter,
     ShorthandComponentFormatter as ShorthandComponentFormatter,

src/django_components/attributes.py

@@ -4,37 +4,46 @@
 
 from typing import Any, Dict, List, Mapping, Optional, Tuple
 
-from django.template import Context, Node
+from django.template import Context
 from django.utils.html import conditional_escape, format_html
 from django.utils.safestring import SafeString, mark_safe
 
-from django_components.expression import Expression, safe_resolve
+from django_components.expression import RuntimeKwargPairs, RuntimeKwargs
+from django_components.node import BaseNode
 
 HTML_ATTRS_DEFAULTS_KEY = "defaults"
 HTML_ATTRS_ATTRS_KEY = "attrs"
 
 
-class HtmlAttrsNode(Node):
+class HtmlAttrsNode(BaseNode):
     def __init__(
         self,
-        attributes: Optional[Expression],
-        defaults: Optional[Expression],
-        kwargs: List[Tuple[str, Expression]],
+        kwargs: RuntimeKwargs,
+        kwarg_pairs: RuntimeKwargPairs,
+        node_id: Optional[str] = None,
     ):
-        self.attributes = attributes
-        self.defaults = defaults
-        self.kwargs = kwargs
+        super().__init__(nodelist=None, args=None, kwargs=kwargs, node_id=node_id)
+        self.kwarg_pairs = kwarg_pairs
 
     def render(self, context: Context) -> str:
         append_attrs: List[Tuple[str, Any]] = []
 
         # Resolve all data
-        for key, value in self.kwargs:
-            resolved_value = safe_resolve(value, context)
-            append_attrs.append((key, resolved_value))
+        kwargs = self.kwargs.resolve(context)
+        attrs = kwargs.pop(HTML_ATTRS_ATTRS_KEY, None) or {}
+        defaults = kwargs.pop(HTML_ATTRS_DEFAULTS_KEY, None) or {}
 
-        defaults = safe_resolve(self.defaults, context) or {} if self.defaults else {}
-        attrs = safe_resolve(self.attributes, context) or {} if self.attributes else {}
+        kwarg_pairs = self.kwarg_pairs.resolve(context)
+
+        for key, value in kwarg_pairs:
+            if (
+                key in [HTML_ATTRS_ATTRS_KEY, HTML_ATTRS_DEFAULTS_KEY]
+                or key.startswith(f"{HTML_ATTRS_ATTRS_KEY}:")
+                or key.startswith(f"{HTML_ATTRS_DEFAULTS_KEY}:")
+            ):
+                continue
+
+            append_attrs.append((key, value))
 
         # Merge it
         final_attrs = {**defaults, **attrs}

src/django_components/component.py

@@ -23,7 +23,7 @@ from typing import (
 from django.core.exceptions import ImproperlyConfigured
 from django.forms.widgets import Media
 from django.http import HttpRequest, HttpResponse
-from django.template.base import FilterExpression, Node, NodeList, Template, TextNode
+from django.template.base import NodeList, Template, TextNode
 from django.template.context import Context
 from django.template.exceptions import TemplateSyntaxError
 from django.template.loader import get_template
@@ -42,21 +42,23 @@ from django_components.context import (
     make_isolated_context_copy,
     prepare_context,
 )
-from django_components.expression import safe_resolve_dict, safe_resolve_list
+from django_components.expression import Expression, RuntimeKwargs, safe_resolve_list
 from django_components.logger import trace_msg
 from django_components.middleware import is_dependency_middleware_active
+from django_components.node import BaseNode
 from django_components.slots import (
     DEFAULT_SLOT_KEY,
+    SLOT_DATA_KWARG,
+    SLOT_DEFAULT_KWARG,
     FillContent,
     FillNode,
     SlotContent,
     SlotName,
     SlotRef,
-    SlotRenderedContent,
+    SlotResult,
     _nodelist_to_slot_render_func,
     resolve_slots,
 )
-from django_components.template_parser import process_aggregate_kwargs
 from django_components.utils import gen_id
 
 # TODO_DEPRECATE_V1 - REMOVE IN V1, users should use top-level import instead
@@ -571,7 +573,11 @@ class Component(Generic[ArgsType, KwargsType, DataType, SlotsType], metaclass=Co
                 )
             else:
 
-                def content_func(ctx: Context, kwargs: Dict[str, Any], slot_ref: SlotRef) -> SlotRenderedContent:
+                def content_func(  # type: ignore[misc]
+                    ctx: Context,
+                    kwargs: Dict[str, Any],
+                    slot_ref: SlotRef,
+                ) -> SlotResult:
                     rendered = content(ctx, kwargs, slot_ref)
                     return conditional_escape(rendered) if escape_content else rendered
 
@@ -583,25 +589,23 @@ class Component(Generic[ArgsType, KwargsType, DataType, SlotsType], metaclass=Co
         return slot_fills
 
 
-class ComponentNode(Node):
+class ComponentNode(BaseNode):
     """Django.template.Node subclass that renders a django-components component"""
 
     def __init__(
         self,
         name: str,
-        context_args: List[FilterExpression],
-        context_kwargs: Mapping[str, FilterExpression],
+        args: List[Expression],
+        kwargs: RuntimeKwargs,
         isolated_context: bool = False,
         fill_nodes: Optional[List[FillNode]] = None,
-        component_id: Optional[str] = None,
+        node_id: Optional[str] = None,
     ) -> None:
-        self.component_id = component_id or gen_id()
+        super().__init__(nodelist=NodeList(fill_nodes), args=args, kwargs=kwargs, node_id=node_id)
+
         self.name = name
-        self.context_args = context_args or []
-        self.context_kwargs = context_kwargs or {}
         self.isolated_context = isolated_context
         self.fill_nodes = fill_nodes or []
-        self.nodelist = NodeList(fill_nodes)
 
     def __repr__(self) -> str:
         return "<ComponentNode: {}. Contents: {!r}>".format(
@@ -610,16 +614,15 @@ class ComponentNode(Node):
         )
 
     def render(self, context: Context) -> str:
-        trace_msg("RENDR", "COMP", self.name, self.component_id)
+        trace_msg("RENDR", "COMP", self.name, self.node_id)
 
         component_cls: Type[Component] = registry.get(self.name)
 
         # Resolve FilterExpressions and Variables that were passed as args to the
         # component, then call component's context method
         # to get values to insert into the context
-        resolved_context_args = safe_resolve_list(self.context_args, context)
-        resolved_context_kwargs = safe_resolve_dict(self.context_kwargs, context)
-        resolved_context_kwargs = process_aggregate_kwargs(resolved_context_kwargs)
+        args = safe_resolve_list(context, self.args)
+        kwargs = self.kwargs.resolve(context)
 
         is_default_slot = len(self.fill_nodes) == 1 and self.fill_nodes[0].is_implicit
         if is_default_slot:
@@ -635,26 +638,25 @@ class ComponentNode(Node):
             for fill_node in self.fill_nodes:
                 # Note that outer component context is used to resolve variables in
                 # fill tag.
-                resolved_name = fill_node.name_fexp.resolve(context)
+                resolved_name = fill_node.name.resolve(context)
                 if resolved_name in fill_content:
                     raise TemplateSyntaxError(
                         f"Multiple fill tags cannot target the same slot name: "
                         f"Detected duplicate fill tag name '{resolved_name}'."
                     )
 
-                resolved_slot_default_var = fill_node.resolve_slot_default(context, self.name)
-                resolved_slot_data_var = fill_node.resolve_slot_data(context, self.name)
+                fill_kwargs = fill_node.resolve_kwargs(context, self.name)
                 fill_content[resolved_name] = FillContent(
                     content_func=_nodelist_to_slot_render_func(fill_node.nodelist),
-                    slot_default_var=resolved_slot_default_var,
-                    slot_data_var=resolved_slot_data_var,
+                    slot_default_var=fill_kwargs[SLOT_DEFAULT_KWARG],
+                    slot_data_var=fill_kwargs[SLOT_DATA_KWARG],
                 )
 
         component: Component = component_cls(
             registered_name=self.name,
             outer_context=context,
             fill_content=fill_content,
-            component_id=self.component_id,
+            component_id=self.node_id,
         )
 
         # Prevent outer context from leaking into the template of the component
@@ -663,11 +665,11 @@ class ComponentNode(Node):
 
         output = component._render(
             context=context,
-            args=resolved_context_args,
-            kwargs=resolved_context_kwargs,
+            args=args,
+            kwargs=kwargs,
         )
 
-        trace_msg("RENDR", "COMP", self.name, self.component_id, "...Done!")
+        trace_msg("RENDR", "COMP", self.name, self.node_id, "...Done!")
         return output
 
 

src/django_components/expression.py

@@ -1,50 +1,55 @@
-from typing import Any, Dict, List, Mapping, Optional, Union
+from typing import Any, Dict, List, Mapping, Optional, Tuple, Union
 
-from django.template import Context
+from django.template import Context, TemplateSyntaxError
 from django.template.base import FilterExpression, Parser
 
-
-class AggregateFilterExpression:
-    def __init__(self, dict: Dict[str, FilterExpression]) -> None:
-        self.dict = dict
+Expression = Union[FilterExpression]
+RuntimeKwargsInput = Dict[str, Expression]
+RuntimeKwargPairsInput = List[Tuple[str, Expression]]
 
 
-Expression = Union[FilterExpression, AggregateFilterExpression]
+class RuntimeKwargs:
+    def __init__(self, kwargs: RuntimeKwargsInput) -> None:
+        self.kwargs = kwargs
+
+    def resolve(self, context: Context) -> Dict[str, Any]:
+        resolved_kwargs = safe_resolve_dict(context, self.kwargs)
+        return process_aggregate_kwargs(resolved_kwargs)
 
 
-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
+class RuntimeKwargPairs:
+    def __init__(self, kwarg_pairs: RuntimeKwargPairsInput) -> None:
+        self.kwarg_pairs = kwarg_pairs
+
+    def resolve(self, context: Context) -> List[Tuple[str, Any]]:
+        resolved_kwarg_pairs: List[Tuple[str, Any]] = []
+        for key, kwarg in self.kwarg_pairs:
+            resolved_kwarg_pairs.append((key, kwarg.resolve(context)))
+
+        return resolved_kwarg_pairs
 
 
-def safe_resolve_list(args: List[Expression], context: Context) -> List:
-    return [safe_resolve(arg, context) for arg in args]
+def is_identifier(value: Any) -> bool:
+    if not isinstance(value, str):
+        return False
+    if not value.isidentifier():
+        return False
+    return True
+
+
+def safe_resolve_list(context: Context, args: List[Expression]) -> List:
+    return [arg.resolve(context) for arg in args]
 
 
 def safe_resolve_dict(
-    kwargs: Union[Mapping[str, Expression], Dict[str, Expression]],
     context: Context,
-) -> Dict:
-    return {key: safe_resolve(kwarg, context) for key, kwarg in kwargs.items()}
+    kwargs: Dict[str, Expression],
+) -> Dict[str, Any]:
+    result = {}
 
-
-def safe_resolve(context_item: Expression, context: Context) -> Any:
-    """Resolve FilterExpressions and Variables in context if possible. Return other items unchanged."""
-    if isinstance(context_item, AggregateFilterExpression):
-        return safe_resolve_dict(context_item.dict, context)
-
-    return context_item.resolve(context) if hasattr(context_item, "resolve") else context_item
+    for key, kwarg in kwargs.items():
+        result[key] = kwarg.resolve(context)
+    return result
 
 
 def resolve_string(
@@ -57,7 +62,90 @@ def resolve_string(
     return parser.compile_filter(s).resolve(context)
 
 
+def is_kwarg(key: str) -> bool:
+    return "=" in key
+
+
 def is_aggregate_key(key: str) -> bool:
     # NOTE: If we get a key that starts with `:`, like `:class`, we do not split it.
     # This syntax is used by Vue and AlpineJS.
     return ":" in key and not key.startswith(":")
+
+
+def process_aggregate_kwargs(kwargs: Mapping[str, Any]) -> Dict[str, Any]:
+    """
+    This function aggregates "prefixed" kwargs into dicts. "Prefixed" kwargs
+    start with some prefix delimited with `:` (e.g. `attrs:`).
+
+    Example:
+    ```py
+    process_component_kwargs({"abc:one": 1, "abc:two": 2, "def:three": 3, "four": 4})
+    # {"abc": {"one": 1, "two": 2}, "def": {"three": 3}, "four": 4}
+    ```
+
+    ---
+
+    We want to support a use case similar to Vue's fallthrough attributes.
+    In other words, where a component author can designate a prop (input)
+    which is a dict and which will be rendered as HTML attributes.
+
+    This is useful for allowing component users to tweak styling or add
+    event handling to the underlying HTML. E.g.:
+
+    `class="pa-4 d-flex text-black"` or `@click.stop="alert('clicked!')"`
+
+    So if the prop is `attrs`, and the component is called like so:
+    ```django
+    {% component "my_comp" attrs=attrs %}
+    ```
+
+    then, if `attrs` is:
+    ```py
+    {"class": "text-red pa-4", "@click": "dispatch('my_event', 123)"}
+    ```
+
+    and the component template is:
+    ```django
+    <div {% html_attrs attrs add:class="extra-class" %}></div>
+    ```
+
+    Then this renders:
+    ```html
+    <div class="text-red pa-4 extra-class" @click="dispatch('my_event', 123)" ></div>
+    ```
+
+    However, this way it is difficult for the component user to define the `attrs`
+    variable, especially if they want to combine static and dynamic values. Because
+    they will need to pre-process the `attrs` dict.
+
+    So, instead, we allow to "aggregate" props into a dict. So all props that start
+    with `attrs:`, like `attrs:class="text-red"`, will be collected into a dict
+    at key `attrs`.
+
+    This provides sufficient flexiblity to make it easy for component users to provide
+    "fallthrough attributes", and sufficiently easy for component authors to process
+    that input while still being able to provide their own keys.
+    """
+    processed_kwargs = {}
+    nested_kwargs: Dict[str, Dict[str, Any]] = {}
+    for key, val in kwargs.items():
+        if not is_aggregate_key(key):
+            processed_kwargs[key] = val
+            continue
+
+        # NOTE: Trim off the prefix from keys
+        prefix, sub_key = key.split(":", 1)
+        if prefix not in nested_kwargs:
+            nested_kwargs[prefix] = {}
+        nested_kwargs[prefix][sub_key] = val
+
+    # Assign aggregated values into normal input
+    for key, val in nested_kwargs.items():
+        if key in processed_kwargs:
+            raise TemplateSyntaxError(
+                f"Received argument '{key}' both as a regular input ({key}=...)"
+                f" and as an aggregate dict ('{key}:key=...'). Must be only one of the two"
+            )
+        processed_kwargs[key] = val
+
+    return processed_kwargs

src/django_components/node.py

@@ -5,6 +5,25 @@ from django.template.base import Node, NodeList, TextNode
 from django.template.defaulttags import CommentNode
 from django.template.loader_tags import ExtendsNode, IncludeNode, construct_relative_path
 
+from django_components.expression import Expression, RuntimeKwargs
+from django_components.utils import gen_id
+
+
+class BaseNode(Node):
+    """Shared behavior for our subclasses of Django's `Node`"""
+
+    def __init__(
+        self,
+        nodelist: Optional[NodeList] = None,
+        node_id: Optional[str] = None,
+        args: Optional[List[Expression]] = None,
+        kwargs: Optional[RuntimeKwargs] = None,
+    ):
+        self.nodelist = nodelist or NodeList()
+        self.node_id = node_id or gen_id()
+        self.args = args or []
+        self.kwargs = kwargs or RuntimeKwargs({})
+
 
 def nodelist_has_content(nodelist: NodeList) -> bool:
     for node in nodelist:

src/django_components/provide.py

@@ -1,17 +1,17 @@
-from typing import Dict, Optional
+from typing import Optional
 
 from django.template import Context
-from django.template.base import FilterExpression, Node, NodeList
+from django.template.base import NodeList
 from django.utils.safestring import SafeString
 
 from django_components.context import set_provided_context_var
-from django_components.expression import safe_resolve_dict
+from django_components.expression import RuntimeKwargs
 from django_components.logger import trace_msg
-from django_components.template_parser import process_aggregate_kwargs
+from django_components.node import BaseNode
 from django_components.utils import gen_id
 
 
-class ProvideNode(Node):
+class ProvideNode(BaseNode):
     """
     Implementation of the `{% provide %}` tag.
     For more info see `Component.inject`.
@@ -22,29 +22,29 @@ class ProvideNode(Node):
         name: str,
         nodelist: NodeList,
         node_id: Optional[str] = None,
-        provide_kwargs: Optional[Dict[str, FilterExpression]] = None,
+        kwargs: Optional[RuntimeKwargs] = None,
     ):
+        super().__init__(nodelist=nodelist, args=None, kwargs=kwargs, node_id=node_id)
+
         self.name = name
         self.nodelist = nodelist
         self.node_id = node_id or gen_id()
-        self.provide_kwargs = provide_kwargs or {}
+        self.kwargs = kwargs or RuntimeKwargs({})
 
     def __repr__(self) -> str:
-        return f"<Provide Node: {self.name}. Contents: {repr(self.nodelist)}. Data: {self.provide_kwargs}>"
+        return f"<Provide Node: {self.name}. Contents: {repr(self.nodelist)}. Data: {self.provide_kwargs.kwargs}>"
 
     def render(self, context: Context) -> SafeString:
         trace_msg("RENDR", "PROVIDE", self.name, self.node_id)
 
-        data = safe_resolve_dict(self.provide_kwargs, context)
-        # Allow user to use the var:key=value syntax
-        data = process_aggregate_kwargs(data)
+        kwargs = self.kwargs.resolve(context)
 
         # NOTE: The "provided" kwargs are meant to be shared privately, meaning that components
         # have to explicitly opt in by using the `Component.inject()` method. That's why we don't
         # add the provided kwargs into the Context.
         with context.update({}):
             # "Provide" the data to child nodes
-            set_provided_context_var(context, self.name, data)
+            set_provided_context_var(context, self.name, kwargs)
 
             output = self.nodelist.render(context)
 

src/django_components/slots.py

@@ -2,7 +2,8 @@ import difflib
 import json
 import re
 from collections import deque
-from typing import Any, Callable, Dict, List, Mapping, NamedTuple, Optional, Set, Tuple, Type, Union
+from dataclasses import dataclass
+from typing import Any, Dict, Generic, List, Mapping, NamedTuple, Optional, Protocol, Set, Tuple, Type, TypeVar, Union
 
 from django.template import Context, Template
 from django.template.base import FilterExpression, Node, NodeList, Parser, TextNode
@@ -16,26 +17,38 @@ from django_components.context import (
     _INJECT_CONTEXT_KEY_PREFIX,
     _ROOT_CTX_CONTEXT_KEY,
 )
-from django_components.expression import Expression, resolve_expression_as_identifier, safe_resolve_dict
+from django_components.expression import RuntimeKwargs, is_identifier
 from django_components.logger import trace_msg
-from django_components.node import NodeTraverse, nodelist_has_content, walk_nodelist
-from django_components.utils import gen_id
+from django_components.node import BaseNode, NodeTraverse, nodelist_has_content, walk_nodelist
+
+TSlotData = TypeVar("TSlotData", bound=Mapping, contravariant=True)
 
 DEFAULT_SLOT_KEY = "_DJANGO_COMPONENTS_DEFAULT_SLOT"
+SLOT_DATA_KWARG = "data"
+SLOT_DEFAULT_KWARG = "default"
+SLOT_REQUIRED_KEYWORD = "required"
+SLOT_DEFAULT_KEYWORD = "default"
 
-SlotRenderedContent = Union[str, SafeString]
-SlotRenderFunc = Callable[[Context, Dict[str, Any], "SlotRef"], SlotRenderedContent]
 
-# Type aliases
+# Public types
+SlotResult = Union[str, SafeString]
 
+
+class SlotFunc(Protocol, Generic[TSlotData]):
+    def __call__(self, ctx: Context, slot_data: TSlotData, slot_ref: "SlotRef") -> SlotResult: ...  # noqa E704
+
+
+SlotContent = Union[SlotResult, SlotFunc[TSlotData]]
+
+# Internal type aliases
 SlotId = str
 SlotName = str
 SlotDefaultName = str
 SlotDataName = str
-SlotContent = Union[str, SafeString, SlotRenderFunc]
 
 
-class FillContent(NamedTuple):
+@dataclass(frozen=True)
+class FillContent(Generic[TSlotData]):
     """
     This represents content set with the `{% fill %}` tag, e.g.:
 
@@ -50,7 +63,7 @@ class FillContent(NamedTuple):
     ```
     """
 
-    content_func: SlotRenderFunc
+    content_func: SlotFunc[TSlotData]
     slot_default_var: Optional[SlotDefaultName]
     slot_data_var: Optional[SlotDataName]
 
@@ -75,7 +88,8 @@ class Slot(NamedTuple):
     nodelist: NodeList
 
 
-class SlotFill(NamedTuple):
+@dataclass(frozen=True)
+class SlotFill(Generic[TSlotData]):
     """
     SlotFill describes what WILL be rendered.
 
@@ -85,7 +99,7 @@ class SlotFill(NamedTuple):
     name: str
     escaped_name: str
     is_filled: bool
-    content_func: SlotRenderFunc
+    content_func: SlotFunc[TSlotData]
     context_data: Mapping
     slot_default_var: Optional[SlotDefaultName]
     slot_data_var: Optional[SlotDataName]
@@ -110,22 +124,21 @@ class SlotRef:
         return mark_safe(self._slot.nodelist.render(self._context))
 
 
-class SlotNode(Node):
+class SlotNode(BaseNode):
     def __init__(
         self,
         name: str,
         nodelist: NodeList,
+        node_id: Optional[str] = None,
+        kwargs: Optional[RuntimeKwargs] = None,
         is_required: bool = False,
         is_default: bool = False,
-        node_id: Optional[str] = None,
-        slot_kwargs: Optional[Dict[str, Expression]] = None,
     ):
+        super().__init__(nodelist=nodelist, args=None, kwargs=kwargs, node_id=node_id)
+
         self.name = name
-        self.nodelist = nodelist
         self.is_required = is_required
         self.is_default = is_default
-        self.node_id = node_id or gen_id()
-        self.slot_kwargs = slot_kwargs or {}
 
     @property
     def active_flags(self) -> List[str]:
@@ -171,14 +184,14 @@ class SlotNode(Node):
         # Expose the kwargs that were passed to the `{% slot %}` tag. These kwargs
         # are made available through a variable name that was set on the `{% fill %}`
         # tag.
-        slot_kwargs = safe_resolve_dict(self.slot_kwargs, context)
+        kwargs = self.kwargs.resolve(context)
         data_var = slot_fill.slot_data_var
         if data_var:
             if not data_var.isidentifier():
                 raise TemplateSyntaxError(
                     f"Slot data alias in fill '{self.name}' must be a valid identifier. Got '{data_var}'"
                 )
-            extra_context[data_var] = slot_kwargs
+            extra_context[data_var] = kwargs
 
         # For the user-provided slot fill, we want to use the context of where the slot
         # came from (or current context if configured so)
@@ -187,7 +200,7 @@ class SlotNode(Node):
             # Render slot as a function
             # NOTE: While `{% fill %}` tag has to opt in for the `default` and `data` variables,
             #       the render function ALWAYS receives them.
-            output = slot_fill.content_func(used_ctx, slot_kwargs, slot_ref)
+            output = slot_fill.content_func(used_ctx, kwargs, slot_ref)
 
         trace_msg("RENDR", "SLOT", self.name, self.node_id, msg="...Done!")
         return output
@@ -208,7 +221,7 @@ class SlotNode(Node):
             raise ValueError(f"Unknown value for CONTEXT_BEHAVIOR: '{app_settings.CONTEXT_BEHAVIOR}'")
 
 
-class FillNode(Node):
+class FillNode(BaseNode):
     """
     Set when a `component` tag pair is passed template content that
     excludes `fill` tags. Nodes of this type contribute their nodelists to slots marked
@@ -217,19 +230,16 @@ class FillNode(Node):
 
     def __init__(
         self,
+        name: FilterExpression,
         nodelist: NodeList,
-        name_fexp: FilterExpression,
-        slot_default_var_fexp: Optional[FilterExpression] = None,
-        slot_data_var_fexp: Optional[FilterExpression] = None,
-        is_implicit: bool = False,
+        kwargs: RuntimeKwargs,
         node_id: Optional[str] = None,
+        is_implicit: bool = False,
     ):
-        self.node_id = node_id or gen_id()
-        self.nodelist = nodelist
-        self.name_fexp = name_fexp
-        self.slot_default_var_fexp = slot_default_var_fexp
+        super().__init__(nodelist=nodelist, args=None, kwargs=kwargs, node_id=node_id)
+
+        self.name = name
         self.is_implicit = is_implicit
-        self.slot_data_var_fexp = slot_data_var_fexp
         self.component_id: Optional[str] = None
 
     def render(self, context: Context) -> str:
@@ -240,33 +250,44 @@ class FillNode(Node):
         )
 
     def __repr__(self) -> str:
-        return f"<{type(self)} Name: {self.name_fexp}. Contents: {repr(self.nodelist)}.>"
+        return f"<{type(self)} Name: {self.name}. Contents: {repr(self.nodelist)}.>"
 
-    def resolve_slot_default(self, context: Context, component_name: Optional[str] = None) -> Optional[str]:
-        return self.resolve_fexp("slot default", self.slot_default_var_fexp, context, component_name)
+    def resolve_kwargs(self, context: Context, component_name: Optional[str] = None) -> Dict[str, Optional[str]]:
+        kwargs = self.kwargs.resolve(context)
 
-    def resolve_slot_data(self, context: Context, component_name: Optional[str] = None) -> Optional[str]:
-        return self.resolve_fexp("slot data", self.slot_data_var_fexp, context, component_name)
+        default_key = self._resolve_kwarg(kwargs, SLOT_DEFAULT_KWARG, "slot default", component_name)
+        data_key = self._resolve_kwarg(kwargs, SLOT_DATA_KWARG, "slot data", component_name)
 
-    def resolve_fexp(
+        # data and default cannot be bound to the same variable
+        if data_key and default_key and data_key == default_key:
+            raise RuntimeError(
+                f"Fill {self.name} received the same string for slot default ({SLOT_DEFAULT_KWARG}=...)"
+                f" and slot data ({SLOT_DATA_KWARG}=...)"
+            )
+
+        return {
+            SLOT_DEFAULT_KWARG: default_key,
+            SLOT_DATA_KWARG: data_key,
+        }
+
+    def _resolve_kwarg(
         self,
+        kwargs: Dict[str, Any],
+        key: str,
         name: str,
-        fexp: Optional[FilterExpression],
-        context: Context,
         component_name: Optional[str] = None,
     ) -> Optional[str]:
-        if not fexp:
+        if key not in kwargs:
             return None
 
-        try:
-            resolved_name = resolve_expression_as_identifier(context, fexp)
-        except ValueError as err:
-            raise TemplateSyntaxError(
-                f"Fill tag {name} '{fexp.var}' in component {component_name}"
-                f"does not resolve to a valid Python identifier."
-            ) from err
+        value = kwargs[key]
+        if not is_identifier(value):
+            raise RuntimeError(
+                f"Fill tag {name} in component {component_name}"
+                f"does not resolve to a valid Python identifier, got '{value}'"
+            )
 
-        return resolved_name
+        return value
 
 
 def parse_slot_fill_nodes_from_component_nodelist(
@@ -316,18 +337,18 @@ def _try_parse_as_named_fill_tag_set(
     ComponentNodeCls: Type[Node],
 ) -> List[FillNode]:
     result = []
-    seen_name_fexps: Set[str] = set()
+    seen_names: Set[str] = set()
     for node in nodelist:
         if isinstance(node, FillNode):
             # Check that, after we've resolved the names, that there's still no duplicates.
             # This makes sure that if two different variables refer to same string, we detect
             # them.
-            if node.name_fexp.token in seen_name_fexps:
+            if node.name.token in seen_names:
                 raise TemplateSyntaxError(
                     f"Multiple fill tags cannot target the same slot name: "
-                    f"Detected duplicate fill tag name '{node.name_fexp}'."
+                    f"Detected duplicate fill tag name '{node.name}'."
                 )
-            seen_name_fexps.add(node.name_fexp.token)
+            seen_names.add(node.name.token)
             result.append(node)
         elif isinstance(node, CommentNode):
             pass
@@ -357,7 +378,8 @@ def _try_parse_as_default_fill(
         return [
             FillNode(
                 nodelist=nodelist,
-                name_fexp=FilterExpression(json.dumps(DEFAULT_SLOT_KEY), Parser("")),
+                name=FilterExpression(json.dumps(DEFAULT_SLOT_KEY), Parser("")),
+                kwargs=RuntimeKwargs({}),
                 is_implicit=True,
             )
         ]
@@ -609,8 +631,8 @@ def _escape_slot_name(name: str) -> str:
     return escaped_name
 
 
-def _nodelist_to_slot_render_func(nodelist: NodeList) -> SlotRenderFunc:
-    def render_func(ctx: Context, slot_kwargs: Dict[str, Any], slot_ref: SlotRef) -> SlotRenderedContent:
+def _nodelist_to_slot_render_func(nodelist: NodeList) -> SlotFunc:
+    def render_func(ctx: Context, kwargs: Dict[str, Any], slot_ref: SlotRef) -> SlotResult:
         return nodelist.render(ctx)
 
-    return render_func
+    return render_func  # type: ignore[return-value]

src/django_components/template_parser.py

@@ -5,7 +5,7 @@ Based on Django Slippers v0.6.2 - https://github.com/mixxorz/slippers/blob/main/
 """
 
 import re
-from typing import Any, Dict, List, Mapping, Tuple
+from typing import Any, Dict, List, Tuple
 
 from django.template.base import (
     FILTER_ARGUMENT_SEPARATOR,
@@ -205,88 +205,3 @@ def parse_bits(
             % (name, ", ".join("'%s'" % p for p in unhandled_params))
         )
     return args, kwargs
-
-
-def process_aggregate_kwargs(kwargs: Mapping[str, Any]) -> Dict[str, Any]:
-    """
-    This function aggregates "prefixed" kwargs into dicts. "Prefixed" kwargs
-    start with some prefix delimited with `:` (e.g. `attrs:`).
-
-    Example:
-    ```py
-    process_component_kwargs({"abc:one": 1, "abc:two": 2, "def:three": 3, "four": 4})
-    # {"abc": {"one": 1, "two": 2}, "def": {"three": 3}, "four": 4}
-    ```
-
-    ---
-
-    We want to support a use case similar to Vue's fallthrough attributes.
-    In other words, where a component author can designate a prop (input)
-    which is a dict and which will be rendered as HTML attributes.
-
-    This is useful for allowing component users to tweak styling or add
-    event handling to the underlying HTML. E.g.:
-
-    `class="pa-4 d-flex text-black"` or `@click.stop="alert('clicked!')"`
-
-    So if the prop is `attrs`, and the component is called like so:
-    ```django
-    {% component "my_comp" attrs=attrs %}
-    ```
-
-    then, if `attrs` is:
-    ```py
-    {"class": "text-red pa-4", "@click": "dispatch('my_event', 123)"}
-    ```
-
-    and the component template is:
-    ```django
-    <div {% html_attrs attrs add:class="extra-class" %}></div>
-    ```
-
-    Then this renders:
-    ```html
-    <div class="text-red pa-4 extra-class" @click="dispatch('my_event', 123)" ></div>
-    ```
-
-    However, this way it is difficult for the component user to define the `attrs`
-    variable, especially if they want to combine static and dynamic values. Because
-    they will need to pre-process the `attrs` dict.
-
-    So, instead, we allow to "aggregate" props into a dict. So all props that start
-    with `attrs:`, like `attrs:class="text-red"`, will be collected into a dict
-    at key `attrs`.
-
-    This provides sufficient flexiblity to make it easy for component users to provide
-    "fallthrough attributes", and sufficiently easy for component authors to process
-    that input while still being able to provide their own keys.
-    """
-    processed_kwargs = {}
-    nested_kwargs: Dict[str, Dict[str, Any]] = {}
-    for key, val in kwargs.items():
-        if not is_aggregate_key(key):
-            processed_kwargs[key] = val
-            continue
-
-        # NOTE: Trim off the prefix from keys
-        prefix, sub_key = key.split(":", 1)
-        if prefix not in nested_kwargs:
-            nested_kwargs[prefix] = {}
-        nested_kwargs[prefix][sub_key] = val
-
-    # Assign aggregated values into normal input
-    for key, val in nested_kwargs.items():
-        if key in processed_kwargs:
-            raise TemplateSyntaxError(
-                f"Received argument '{key}' both as a regular input ({key}=...)"
-                f" and as an aggregate dict ('{key}:key=...'). Must be only one of the two"
-            )
-        processed_kwargs[key] = val
-
-    return processed_kwargs
-
-
-def is_aggregate_key(key: str) -> bool:
-    # NOTE: If we get a key that starts with `:`, like `:class`, we do not split it.
-    # This syntax is used by Vue and AlpineJS.
-    return ":" in key and not key.startswith(":")

src/django_components/templatetags/component_tags.py

@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Callable, Dict, List, NamedTuple, Optional, Set, Tuple, Union
+from typing import TYPE_CHECKING, Callable, Dict, List, NamedTuple, Optional, Set, Union
 
 import django.template
 from django.template.base import FilterExpression, NodeList, Parser, Token
@@ -6,11 +6,19 @@ from django.template.exceptions import TemplateSyntaxError
 from django.utils.safestring import SafeString, mark_safe
 
 from django_components.app_settings import ContextBehavior, app_settings
-from django_components.attributes import HtmlAttrsNode
+from django_components.attributes import HTML_ATTRS_ATTRS_KEY, HTML_ATTRS_DEFAULTS_KEY, HtmlAttrsNode
 from django_components.component import RENDERED_COMMENT_TEMPLATE, ComponentNode
 from django_components.component_registry import ComponentRegistry
 from django_components.component_registry import registry as component_registry
-from django_components.expression import AggregateFilterExpression, Expression, resolve_string
+from django_components.expression import (
+    Expression,
+    RuntimeKwargPairs,
+    RuntimeKwargs,
+    RuntimeKwargsInput,
+    is_aggregate_key,
+    is_kwarg,
+    resolve_string,
+)
 from django_components.logger import trace_msg
 from django_components.middleware import (
     CSS_DEPENDENCY_PLACEHOLDER,
@@ -18,9 +26,17 @@ from django_components.middleware import (
     is_dependency_middleware_active,
 )
 from django_components.provide import ProvideNode
-from django_components.slots import FillNode, SlotNode, parse_slot_fill_nodes_from_component_nodelist
+from django_components.slots import (
+    SLOT_DATA_KWARG,
+    SLOT_DEFAULT_KEYWORD,
+    SLOT_DEFAULT_KWARG,
+    SLOT_REQUIRED_KEYWORD,
+    FillNode,
+    SlotNode,
+    parse_slot_fill_nodes_from_component_nodelist,
+)
 from django_components.tag_formatter import get_tag_formatter
-from django_components.template_parser import is_aggregate_key, parse_bits, process_aggregate_kwargs
+from django_components.template_parser import parse_bits
 from django_components.utils import gen_id, is_str_wrapped_in_quotes
 
 if TYPE_CHECKING:
@@ -32,12 +48,6 @@ if TYPE_CHECKING:
 register = django.template.Library()
 
 
-SLOT_REQUIRED_OPTION_KEYWORD = "required"
-SLOT_DEFAULT_OPTION_KEYWORD = "default"
-SLOT_DATA_ATTR = "data"
-SLOT_DEFAULT_ATTR = "default"
-
-
 def _get_components_from_registry(registry: ComponentRegistry) -> List["Component"]:
     """Returns a list unique components from the registry."""
 
@@ -123,7 +133,7 @@ def slot(parser: Parser, token: Token) -> SlotNode:
         parser,
         bits,
         params=["name"],
-        flags=[SLOT_DEFAULT_OPTION_KEYWORD, SLOT_REQUIRED_OPTION_KEYWORD],
+        flags=[SLOT_DEFAULT_KEYWORD, SLOT_REQUIRED_KEYWORD],
         keywordonly_kwargs=True,
         repeatable_kwargs=False,
         end_tag="endslot",
@@ -136,10 +146,10 @@ def slot(parser: Parser, token: Token) -> SlotNode:
     slot_node = SlotNode(
         name=data.name,
         nodelist=body,
-        is_required=tag.flags[SLOT_REQUIRED_OPTION_KEYWORD],
-        is_default=tag.flags[SLOT_DEFAULT_OPTION_KEYWORD],
         node_id=tag.id,
-        slot_kwargs=tag.kwargs,
+        kwargs=tag.kwargs,
+        is_required=tag.flags[SLOT_REQUIRED_KEYWORD],
+        is_default=tag.flags[SLOT_DEFAULT_KEYWORD],
     )
 
     trace_msg("PARSE", "SLOT", data.name, tag.id, "...Done!")
@@ -162,24 +172,23 @@ def fill(parser: Parser, token: Token) -> FillNode:
         parser,
         bits,
         params=["name"],
-        keywordonly_kwargs=[SLOT_DATA_ATTR, SLOT_DEFAULT_ATTR],
+        keywordonly_kwargs=[SLOT_DATA_KWARG, SLOT_DEFAULT_KWARG],
         repeatable_kwargs=False,
         end_tag="endfill",
     )
-    data = _parse_fill_args(parser, tag)
+    slot_name = tag.named_args["name"]
 
-    trace_msg("PARSE", "FILL", str(data.slot_name), tag.id)
+    trace_msg("PARSE", "FILL", str(slot_name), tag.id)
 
     body = tag.parse_body()
     fill_node = FillNode(
         nodelist=body,
-        name_fexp=data.slot_name,
-        slot_default_var_fexp=data.slot_default_var,
-        slot_data_var_fexp=data.slot_data_var,
+        name=slot_name,
         node_id=tag.id,
+        kwargs=tag.kwargs,
     )
 
-    trace_msg("PARSE", "FILL", str(data.slot_name), tag.id, "...Done!")
+    trace_msg("PARSE", "FILL", str(slot_name), tag.id, "...Done!")
     return fill_node
 
 
@@ -216,7 +225,9 @@ def component(parser: Parser, token: Token, tag_name: str) -> ComponentNode:
         repeatable_kwargs=False,
         end_tag=end_tag,
     )
-    data = _parse_component_args(parser, tag)
+
+    # Check for isolated context keyword
+    isolated_context = tag.flags["only"] or app_settings.CONTEXT_BEHAVIOR == ContextBehavior.ISOLATED
 
     trace_msg("PARSE", "COMP", result.component_name, tag.id)
 
@@ -225,16 +236,16 @@ def component(parser: Parser, token: Token, tag_name: str) -> ComponentNode:
 
     # Tag all fill nodes as children of this particular component instance
     for node in fill_nodes:
-        trace_msg("ASSOC", "FILL", node.name_fexp, node.node_id, component_id=tag.id)
+        trace_msg("ASSOC", "FILL", node.name, node.node_id, component_id=tag.id)
         node.component_id = tag.id
 
     component_node = ComponentNode(
         name=result.component_name,
-        context_args=tag.args,
-        context_kwargs=tag.kwargs,
-        isolated_context=data.isolated_context,
+        args=tag.args,
+        kwargs=tag.kwargs,
+        isolated_context=isolated_context,
         fill_nodes=fill_nodes,
-        component_id=tag.id,
+        node_id=tag.id,
     )
 
     trace_msg("PARSE", "COMP", result.component_name, tag.id, "...Done!")
@@ -264,7 +275,7 @@ def provide(parser: Parser, token: Token) -> ProvideNode:
         name=data.key,
         nodelist=body,
         node_id=tag.id,
-        provide_kwargs=tag.kwargs,
+        kwargs=tag.kwargs,
     )
 
     trace_msg("PARSE", "PROVIDE", data.key, tag.id, "...Done!")
@@ -305,17 +316,16 @@ def html_attrs(parser: Parser, token: Token) -> HtmlAttrsNode:
         "html_attrs",
         parser,
         bits,
-        params=["attrs", "defaults"],
-        optional_params=["attrs", "defaults"],
+        params=[HTML_ATTRS_ATTRS_KEY, HTML_ATTRS_DEFAULTS_KEY],
+        optional_params=[HTML_ATTRS_ATTRS_KEY, HTML_ATTRS_DEFAULTS_KEY],
         flags=[],
         keywordonly_kwargs=True,
         repeatable_kwargs=True,
     )
 
     return HtmlAttrsNode(
-        attributes=tag.kwargs.get("attrs"),
-        defaults=tag.kwargs.get("defaults"),
-        kwargs=[(key, val) for key, val in tag.kwarg_pairs if key != "attrs" and key != "defaults"],
+        kwargs=tag.kwargs,
+        kwarg_pairs=tag.kwarg_pairs,
     )
 
 
@@ -324,10 +334,10 @@ class ParsedTag(NamedTuple):
     name: str
     bits: List[str]
     flags: Dict[str, bool]
-    args: List[FilterExpression]
-    named_args: Dict[str, FilterExpression]
-    kwargs: Dict[str, Expression]
-    kwarg_pairs: List[Tuple[str, Expression]]
+    args: List[Expression]
+    named_args: Dict[str, Expression]
+    kwargs: RuntimeKwargs
+    kwarg_pairs: RuntimeKwargPairs
     is_inline: bool
     parse_body: Callable[[], NodeList]
 
@@ -380,17 +390,13 @@ def _parse_tag(
             seen_kwargs.add(key)
 
     for bit in bits:
-        # Extract flags, which are like keywords but without the value part
-        if bit in parsed_flags:
-            parsed_flags[bit] = True
-            continue
-        else:
-            bits_without_flags.append(bit)
+        value = bit
+        bit_is_kwarg = is_kwarg(bit)
 
         # Record which kwargs we've seen, to detect if kwargs were passed in
         # as both aggregate and regular kwargs
-        if "=" in bit:
-            key = bit.split("=")[0]
+        if bit_is_kwarg:
+            key, value = bit.split("=", 1)
 
             # Also pick up on aggregate keys like `attr:key=val`
             if is_aggregate_key(key):
@@ -399,6 +405,14 @@ def _parse_tag(
             else:
                 mark_kwarg_key(key, False)
 
+        else:
+            # Extract flags, which are like keywords but without the value part
+            if value in parsed_flags:
+                parsed_flags[value] = True
+                continue
+
+        bits_without_flags.append(bit)
+
     bits = bits_without_flags
 
     # To support optional args, we need to convert these to kwargs, so `parse_bits`
@@ -415,7 +429,7 @@ def _parse_tag(
         new_params = []
         new_kwargs = []
         for index, bit in enumerate(bits):
-            if "=" in bit or not len(params_to_sort):
+            if is_kwarg(bit) or not len(params_to_sort):
                 # Pass all remaining bits (including current one) as kwargs
                 new_kwargs.extend(bits[index:])
                 break
@@ -436,31 +450,13 @@ def _parse_tag(
             params = [param for param in params_to_sort if param not in optional_params]
 
     # Parse args/kwargs that will be passed to the fill
-    args, raw_kwarg_pairs = parse_bits(
+    args, kwarg_pairs = parse_bits(
         parser=parser,
         bits=bits,
         params=[] if isinstance(params, bool) else params,
         name=tag_name,
     )
 
-    # Post-process args/kwargs - Mark special cases like aggregate dicts
-    # or dynamic expressions
-    pre_aggregate_kwargs: Dict[str, FilterExpression] = {}
-    kwarg_pairs: List[Tuple[str, Expression]] = []
-    for key, val in raw_kwarg_pairs:
-        # NOTE: If a tag allows mutliple kwargs, and we provide a same aggregate key
-        # multiple times (e.g. `attr:class="hidden" and `attr:class="another"`), then
-        # we take only the last instance.
-        if is_aggregate_key(key):
-            pre_aggregate_kwargs[key] = val
-        else:
-            kwarg_pairs.append((key, val))
-    aggregate_kwargs: Dict[str, Dict[str, FilterExpression]] = process_aggregate_kwargs(pre_aggregate_kwargs)
-
-    for key, agg_dict in aggregate_kwargs.items():
-        entry = (key, AggregateFilterExpression(agg_dict))
-        kwarg_pairs.append(entry)
-
     # Allow only as many positional args as given
     if params != True and len(args) > len(params):  # noqa F712
         raise TemplateSyntaxError(f"Tag '{tag_name}' received unexpected positional arguments: {args[len(params):]}")
@@ -472,7 +468,7 @@ def _parse_tag(
         named_args = {}
 
     # Validate kwargs
-    kwargs: Dict[str, Expression] = {}
+    kwargs: RuntimeKwargsInput = {}
     extra_keywords: Set[str] = set()
     for key, val in kwarg_pairs:
         # Check if key allowed
@@ -506,8 +502,8 @@ def _parse_tag(
         flags=parsed_flags,
         args=args,
         named_args=named_args,
-        kwargs=kwargs,
-        kwarg_pairs=kwarg_pairs,
+        kwargs=RuntimeKwargs(kwargs),
+        kwarg_pairs=RuntimeKwargPairs(kwarg_pairs),
         # NOTE: We defer parsing of the body, so we have the chance to call the tracing
         # loggers before the parsing. This is because, if the body contains any other
         # tags, it will trigger their tag handlers. So the code called AFTER
@@ -526,20 +522,6 @@ def _parse_tag_body(parser: Parser, end_tag: str, inline: bool) -> NodeList:
     return body
 
 
-class ParsedComponentTag(NamedTuple):
-    isolated_context: bool
-
-
-def _parse_component_args(
-    parser: Parser,
-    tag: ParsedTag,
-) -> ParsedComponentTag:
-    # Check for isolated context keyword
-    isolated_context = tag.flags["only"] or app_settings.CONTEXT_BEHAVIOR == ContextBehavior.ISOLATED
-
-    return ParsedComponentTag(isolated_context=isolated_context)
-
-
 class ParsedSlotTag(NamedTuple):
     name: str
 
@@ -548,7 +530,10 @@ def _parse_slot_args(
     parser: Parser,
     tag: ParsedTag,
 ) -> ParsedSlotTag:
-    slot_name = tag.named_args["name"].token
+    slot_name_expr = tag.named_args["name"]
+    if not isinstance(slot_name_expr, FilterExpression):
+        raise TemplateSyntaxError(f"Slot name must be string literal, got {slot_name_expr}")
+    slot_name = slot_name_expr.token
     if not is_str_wrapped_in_quotes(slot_name):
         raise TemplateSyntaxError(f"'{tag.name}' name must be a string 'literal', got {slot_name}.")
 
@@ -557,46 +542,6 @@ def _parse_slot_args(
     return ParsedSlotTag(name=slot_name)
 
 
-class ParsedFillTag(NamedTuple):
-    slot_name: FilterExpression
-    slot_default_var: Optional[FilterExpression]
-    slot_data_var: Optional[FilterExpression]
-
-
-def _parse_fill_args(
-    parser: Parser,
-    tag: ParsedTag,
-) -> ParsedFillTag:
-    slot_name_fexp = tag.named_args["name"]
-
-    # Extract known kwargs
-    slot_data_var_fexp: Optional[FilterExpression] = tag.kwargs.get(SLOT_DATA_ATTR)
-    if slot_data_var_fexp and not is_str_wrapped_in_quotes(slot_data_var_fexp.token):
-        raise TemplateSyntaxError(
-            f"Value of '{SLOT_DATA_ATTR}' in '{tag.name}' tag must be a string literal, got '{slot_data_var_fexp}'"
-        )
-
-    slot_default_var_fexp: Optional[FilterExpression] = tag.kwargs.get(SLOT_DEFAULT_ATTR)
-    if slot_default_var_fexp and not is_str_wrapped_in_quotes(slot_default_var_fexp.token):
-        raise TemplateSyntaxError(
-            f"Value of '{SLOT_DEFAULT_ATTR}' in '{tag.name}' tag must be a string literal,"
-            f" got '{slot_default_var_fexp}'"
-        )
-
-    # data and default cannot be bound to the same variable
-    if slot_data_var_fexp and slot_default_var_fexp and slot_data_var_fexp.token == slot_default_var_fexp.token:
-        raise TemplateSyntaxError(
-            f"'{tag.name}' received the same string for slot default ({SLOT_DEFAULT_ATTR}=...)"
-            f" and slot data ({SLOT_DATA_ATTR}=...)"
-        )
-
-    return ParsedFillTag(
-        slot_name=slot_name_fexp,
-        slot_default_var=slot_default_var_fexp,
-        slot_data_var=slot_data_var_fexp,
-    )
-
-
 class ParsedProvideTag(NamedTuple):
     key: str
 
@@ -605,9 +550,12 @@ def _parse_provide_args(
     parser: Parser,
     tag: ParsedTag,
 ) -> ParsedProvideTag:
-    provide_key = tag.named_args["name"].token
+    provide_key_expr = tag.named_args["name"]
+    if not isinstance(provide_key_expr, FilterExpression):
+        raise TemplateSyntaxError(f"Provide key must be string literal, got {provide_key_expr}")
+    provide_key = provide_key_expr.token
     if not is_str_wrapped_in_quotes(provide_key):
-        raise TemplateSyntaxError(f"'{tag.name}' key must be a string 'literal'.")
+        raise TemplateSyntaxError(f"'{tag.name}' key must be a string 'literal', got {provide_key}")
 
     provide_key = resolve_string(provide_key, parser)
 

tests/test_expression.py

@@ -0,0 +1,60 @@
+"""Catch-all for tests that use template tags and don't fit other files"""
+
+from typing import Dict
+
+from django.template import Context, Template
+from django.template.base import Parser
+
+from django_components.expression import safe_resolve_dict, safe_resolve_list
+
+from .django_test_setup import setup_test_config
+from .testutils import BaseTestCase
+
+setup_test_config({"autodiscover": False})
+
+
+engine = Template("").engine
+default_parser = Parser("", engine.template_libraries, engine.template_builtins)
+
+
+def make_context(d: Dict):
+    ctx = Context(d)
+    ctx.template = Template("")
+    return ctx
+
+
+#######################
+# TESTS
+#######################
+
+
+class ResolveTests(BaseTestCase):
+    def test_safe_resolve(self):
+        expr = default_parser.compile_filter("var_abc")
+
+        ctx = make_context({"var_abc": 123})
+        self.assertEqual(
+            expr.resolve(ctx),
+            123,
+        )
+
+        ctx2 = make_context({"var_xyz": 123})
+        self.assertEqual(expr.resolve(ctx2), "")
+
+    def test_safe_resolve_list(self):
+        exprs = [default_parser.compile_filter(f"var_{char}") for char in "abc"]
+
+        ctx = make_context({"var_a": 123, "var_b": [{}, {}]})
+        self.assertEqual(
+            safe_resolve_list(ctx, exprs),
+            [123, [{}, {}], ""],
+        )
+
+    def test_safe_resolve_dict(self):
+        exprs = {char: default_parser.compile_filter(f"var_{char}") for char in "abc"}
+
+        ctx = make_context({"var_a": 123, "var_b": [{}, {}]})
+        self.assertEqual(
+            safe_resolve_dict(ctx, exprs),
+            {"a": 123, "b": [{}, {}], "c": ""},
+        )

tests/test_template_parser.py

@@ -2,8 +2,12 @@ from django.template import Context, Template
 from django.template.base import Parser
 
 from django_components import Component, registry, types
-from django_components.component import safe_resolve_dict, safe_resolve_list
-from django_components.template_parser import is_aggregate_key, process_aggregate_kwargs
+from django_components.expression import (
+    is_aggregate_key,
+    process_aggregate_kwargs,
+    safe_resolve_dict,
+    safe_resolve_list,
+)
 from django_components.templatetags.component_tags import _parse_tag
 
 from .django_test_setup import setup_test_config
@@ -18,9 +22,9 @@ class ParserTest(BaseTestCase):
         tag = _parse_tag("component", Parser(""), bits, params=["num", "var"], keywordonly_kwargs=True)
 
         ctx = {"myvar": {"a": "b"}, "val2": 1}
-        args = safe_resolve_list(tag.args, ctx)
-        named_args = safe_resolve_dict(tag.named_args, ctx)
-        kwargs = safe_resolve_dict(tag.kwargs, ctx)
+        args = safe_resolve_list(ctx, tag.args)
+        named_args = safe_resolve_dict(ctx, tag.named_args)
+        kwargs = tag.kwargs.resolve(ctx)
 
         self.assertListEqual(args, [42, {"a": "b"}])
         self.assertDictEqual(named_args, {"num": 42, "var": {"a": "b"}})
@@ -38,8 +42,8 @@ class ParserTest(BaseTestCase):
         tag = _parse_tag("component", Parser(""), bits, keywordonly_kwargs=True)
 
         ctx = Context({"date": 2024, "bzz": "fzz"})
-        args = safe_resolve_list(tag.args, ctx)
-        kwargs = safe_resolve_dict(tag.kwargs, ctx)
+        args = safe_resolve_list(ctx, tag.args)
+        kwargs = tag.kwargs.resolve(ctx)
 
         self.assertListEqual(args, [])
         self.assertDictEqual(

tests/test_templatetags_slot_fill.py

@@ -822,8 +822,8 @@ class ScopedSlotTest(BaseTestCase):
             {% endcomponent %}
         """
         with self.assertRaisesMessage(
-            TemplateSyntaxError,
-            "'fill' received the same string for slot default (default=...) and slot data (data=...)",
+            RuntimeError,
+            'Fill "my_slot" received the same string for slot default (default=...) and slot data (data=...)',
         ):
             Template(template).render(Context())