feat: support functools.partial handlers

Handlers can now be wrapped by `functools.partial`,
and take arbitrary arguments.

Author: Sacrimento

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/), and this project
 adheres to [Semantic Versioning](https://semver.org/).
 
+## [Unreleased]
+
+- [unreleased]: https://github.com/rogdham/bigxml/compare/v0.10.0...HEAD
+
+### :rocket: Added
+
+- Support `functools.partial` handlers
+
 ## [0.10.0] - 2023-04-22
 
 [0.10.0]: https://github.com/rogdham/bigxml/compare/v0.9.0...v0.10.0

docs/src/handlers.md

@@ -6,6 +6,11 @@ The methods `iter_from` and `return_from` take _handlers_ as arguments.
 
 A handler can be a generator function taking a _node_ as an argument.
 
+!!! Tip
+
+    A handler can take more than a node argument, by using `functools.partial`.
+    See [this recipe](recipes.md#arbitrary-handler-args) for examples.
+
 Such functions are usually decorated with `xml_handle_element` or `xml_handle_text`, to
 restrict the type of nodes they are called with.
 
@@ -97,6 +102,11 @@ argument is supplied with the encountered node:
     <__main__.Cart object...> for user Alice
     <__main__.Cart object...> for user Bob
 
+!!! Tip
+
+    `__init__` can take more than a node argument, by using `functools.partial`.
+    See [this recipe](recipes.md#arbitrary-handler-args) for examples.
+
 ### Class methods as sub-handlers
 
 The methods decorated with `xml_handle_element` or `xml_handle_text` are used as

docs/src/recipes.md

@@ -125,9 +125,7 @@ the `__post_init__` method:
 !!! Warning
 
     The `node` attribute is an `InitVar`, so that it is passed to `__post_init__` but
-    not stored in class attributes. It must be the only mandatory field, since the class
-    is automatically instantiated with only one argument (the node). For more details,
-    see [class handlers](handlers.md#classes).
+    not stored in class attributes.
 
 ## Yielding data in a class `__init__` {: #yield-in-init }
 
@@ -178,6 +176,43 @@ Instead, you can define a custom `xml_handler` method:
     product: 9780099580485
     END cart parsing for user Bob
 
+## Passing arbitrary arguments to handlers {: #arbitrary-handler-args}
+
+You may want to pass arbitrary arguments to your handlers. This is achievable by
+using `functools.partial`.
+
+For example, let's say you only want to yield fast vehicles from this vehicle file:
+
+    :::xml filename=vehicles.xml
+    <vehicles>
+        <vehicle speed="300">Train</vehicle>
+        <vehicle speed="30">Boat</vehicle>
+        <vehicle speed="80">Car</vehicle>
+        <vehicle speed="900">Plane</vehicle>
+    </vehicles>
+
+You can pass the desired speed threshold directly to the handler
+by using `functools.partial`:
+
+    :::python
+    >>> from functools import partial
+    >>> @xml_handle_element("vehicles", "vehicle")
+    ... def handler(speed_threshold, node):
+    ...     if int(node.attributes['speed']) > speed_threshold:
+    ...         yield node.text
+
+    >>> with open("vehicles.xml", "rb") as stream:
+    ...     for vehicle in Parser(stream).iter_from(partial(handler, 150)):
+    ...         print(vehicle)
+    Train
+    Plane
+
+!!! Warning
+
+    If the parameter is positional-only, it must come before the `node` argument.
+
+This behavior also work for class (and dataclasses) handlers.
+
 ## Streams without root {: #no-root }
 
 In some cases, you may be parsing a stream of XML elements that follow each other

src/bigxml/handler_creator.py

@@ -1,4 +1,5 @@
 from dataclasses import is_dataclass
+from functools import partial
 from inspect import getmembers, isclass
 from typing import (
     TYPE_CHECKING,
@@ -55,7 +56,12 @@ class _HandlerTree:
     def __init__(self, path: Tuple[str, ...] = ()) -> None:
         self.path: Tuple[str, ...] = path
         self.children: Dict[str, _HandlerTree] = {}
-        self.handler: Optional[Callable[..., Iterable[object]]] = None
+        self.handler: Optional[
+            Union[
+                Callable[..., Iterable[object]],
+                partial[Callable[..., Iterable[object]]],
+            ]
+        ] = None
 
     def add_handler(
         self,
@@ -126,9 +132,14 @@ def handle(
         self, node: Union["XMLElement", "XMLText"]
     ) -> Optional[Iterable[object]]:
         if self.handler:
-            if isclass(self.handler):
-                return self._handle_from_class(self.handler, node)
-            return self.handler(node)
+            if isclass(
+                self.handler.func if isinstance(self.handler, partial) else self.handler
+            ):
+                return self._handle_from_class(cast(Type[Any], self.handler), node)
+            return cast(
+                Callable[[Union["XMLElement", "XMLText"]], Iterable[object]],
+                self.handler,
+            )(node)
 
         child: Optional[_HandlerTree] = None
         namespace = getattr(node, "namespace", None)

src/bigxml/marks.py

@@ -1,17 +1,25 @@
+from functools import partial
 from typing import Tuple
 
 __ATTR_MARK_NAME = "_xml_handlers_on"
 
 
+def _unwrap_partials(obj: object) -> object:
+    if isinstance(obj, partial):
+        return obj.func
+    return obj
+
+
 def has_marks(obj: object) -> bool:
-    return hasattr(obj, __ATTR_MARK_NAME)
+    return hasattr(_unwrap_partials(obj), __ATTR_MARK_NAME)
 
 
 def get_marks(obj: object) -> Tuple[Tuple[str, ...], ...]:
-    return getattr(obj, __ATTR_MARK_NAME, ())
+    return getattr(_unwrap_partials(obj), __ATTR_MARK_NAME, ())
 
 
 def add_mark(obj: object, mark: Tuple[str, ...]) -> None:
+    obj = _unwrap_partials(obj)
     marks = get_marks(obj)
     marks += (mark,)
     setattr(obj, __ATTR_MARK_NAME, marks)

tests/unit/test_handler_creator.py

@@ -149,6 +149,24 @@ def catchall(
     test_create_handler(catchall)
 
 
+@cases(
+    (("a",), "foo: catchall", "a"),
+    (("{foo}a",), "foo: catchall", "{foo}a"),
+    (("d0", "d1"), "foo: catchall", "d0"),
+    (("d0", "d1", "d2"), "foo: catchall", "d0"),
+    ((":text:",), "foo: catchall", ":text:"),
+)
+def test_one_partial_catchall(test_create_handler: TEST_CREATE_HANDLER_TYPE) -> None:
+    def catchall(
+        ctx: str, node: Union[XMLElement, XMLText]
+    ) -> Iterator[Tuple[str, Union[XMLElement, XMLText]]]:
+        yield (f"{ctx}: catchall", node)
+
+    partial_handler = partial(catchall, "foo")
+
+    test_create_handler(partial_handler)
+
+
 @cases(
     (("a",), "0", "a"),
     (("{foo}a",), "1", "{foo}a"),
@@ -448,6 +466,20 @@ class Handler:
     assert isinstance(items[0], Handler)
 
 
+def test_partial_class_without_subhandler() -> None:
+    @xml_handle_element("x")
+    class Handler:
+        def __init__(self, ctx: str) -> None:
+            self.ctx = ctx
+
+    partial_handler = partial(Handler, "foo")
+    nodes = create_nodes("x", "y")
+    handler = create_handler(partial_handler)
+    items = list(handler(nodes[0]))
+    assert len(items) == 1
+    assert isinstance(items[0], Handler)
+
+
 @pytest.mark.parametrize("init_mandatory", [False, True])
 @pytest.mark.parametrize("init_optional", [False, True])
 def test_class_init(init_mandatory: bool, init_optional: bool) -> None:
@@ -581,6 +613,21 @@ def __init__(self, node: XMLElement, answer: int) -> None:
     assert "Add a default value for dataclass fields" not in str(excinfo.value)
 
 
+def test_partial_class_multiple_mandatory_parameters() -> None:
+    @xml_handle_element("x")
+    class Handler:
+        def __init__(self, before: str, node: XMLElement, after: str) -> None:
+            pass
+
+    partial_handler = partial(Handler, "before", after="after")
+    nodes = create_nodes("x", "y")
+    handler = create_handler(partial_handler)
+    items = list(handler(nodes[0]))
+
+    assert len(items) == 1
+    assert isinstance(items[0], Handler)
+
+
 def test_dataclass_init_two_mandatory_parameters() -> None:
     @xml_handle_element("x")
     @dataclass
@@ -598,6 +645,23 @@ class Handler:
     assert "Add a default value for dataclass fields" in str(excinfo.value)
 
 
+def test_partial_dataclass_two_mandatory_parameters() -> None:
+    @xml_handle_element("x")
+    @dataclass
+    class Handler:
+        before: str
+        node: XMLElement
+        after: str
+
+    partial_handler = partial(Handler, "before", after="after")
+    nodes = create_nodes("x", "y")
+    handler = create_handler(partial_handler)
+    items = list(handler(nodes[0]))
+
+    assert len(items) == 1
+    assert isinstance(items[0], Handler)
+
+
 def test_class_init_crash() -> None:
     @xml_handle_element("x")
     class Handler:

tests/unit/test_handler_marker.py

@@ -1,3 +1,4 @@
+from functools import partial
 from typing import Iterator, Union
 
 import pytest
@@ -15,6 +16,16 @@ def fct(node: XMLElement) -> Iterator[str]:
     assert get_marks(fct) == (("abc", "def"),)
 
 
+def test_one_marker_element_on_partial_func() -> None:
+    @xml_handle_element("abc", "def")
+    def fct(ctx: str, node: XMLElement) -> Iterator[str]:
+        yield f"{ctx}: <{node.text}>"
+
+    partial_fct = partial(fct, "foo")
+
+    assert get_marks(partial_fct) == (("abc", "def"),)
+
+
 def test_one_maker_element_on_method() -> None:
     class Klass:
         def __init__(self, multiplier: int) -> None:

tests/unit/test_marks.py

@@ -1,3 +1,5 @@
+from functools import partial
+
 import pytest
 
 from bigxml.marks import add_mark, get_marks, has_marks
@@ -20,3 +22,21 @@ class Markable:
     add_mark(obj, ("def", "ghi", "jkl"))
     assert has_marks(obj)
     assert get_marks(obj) == (("abc",), ("def", "ghi", "jkl"))
+
+
+def test_marks_on_partial() -> None:
+    class Markable:
+        pass
+
+    obj = partial(Markable, "foo")
+
+    assert not has_marks(obj)
+    assert not get_marks(obj)
+
+    add_mark(obj, ("abc",))
+    assert has_marks(obj)
+    assert get_marks(obj) == (("abc",),)
+
+    add_mark(obj, ("def", "ghi", "jkl"))
+    assert has_marks(obj)
+    assert get_marks(obj) == (("abc",), ("def", "ghi", "jkl"))