Construct fragment via fragment[].

This change makes the fragment consistent with elements by using
__getitem__ to specify child nodes.

See #93 for discussion.

Author: pelme

docs/usage.md

@@ -98,8 +98,8 @@ Fragments allow you to wrap a group of nodes (not necessarily elements) so that
 they can be rendered without a wrapping element.
 
 ```pycon
->>> from htpy import p, i, Fragment
->>> content = Fragment("Hello ", None, i["world!"])
+>>> from htpy import p, i, fragment
+>>> content = fragment["Hello ", None, i["world!"]]
 >>> print(content)
 Hello <i>world!</i>
 
@@ -404,8 +404,8 @@ Just like [render_node()](#render-elements-without-a-parent-orphans), there is
 without a parent:
 
 ```pycon
->>> from htpy import li, iter_node
->>> for chunk in iter_node([li["a"], li["b"]]):
+>>> from htpy import li, Fragment
+>>> for chunk in fragment[li["a"], li["b"]]:
 ...     print(f"got a chunk: {chunk!r}")
 ...
 got a chunk: '<li>'

htpy/__init__.py

@@ -197,8 +197,7 @@ def _iter_node_context(x: Node, context_dict: dict[Context[t.Any], t.Any]) -> It
             )
         yield from _iter_node_context(x.func(context_value), context_dict)
     elif isinstance(x, Fragment):
-        for node in x._nodes:  # pyright: ignore [reportPrivateUsage]
-            yield from _iter_node_context(node, context_dict)
+        yield from _iter_node_context(x._node, context_dict)  # pyright: ignore
     elif isinstance(x, str | _HasHtml):
         yield str(_escape(x))
     elif isinstance(x, int):
@@ -348,17 +347,15 @@ def __repr__(self) -> str:
 
 
 class Fragment:
-    """A collection of nodes without a wrapping element.
+    """A collection of nodes without a wrapping element."""
 
-    >>> content = Fragment("Hello ", None, i["world!"])
-    >>> print(content)
-    Hello <i>world!</i>
-    """
+    __slots__ = ("_node", "_allow_init")
 
-    __slots__ = ("_nodes",)
+    def __init__(self, node: Node) -> None:
+        if not hasattr(self, "_allow_init"):
+            raise TypeError("Cannot instantiate Fragment directly. Use fragment[x] instead.")
 
-    def __init__(self, *nodes: Node) -> None:
-        self._nodes = nodes
+        self._node = node
 
     def __iter__(self) -> Iterator[str]:
         return iter_node(self)
@@ -368,14 +365,27 @@ def __str__(self) -> str:
 
     __html__ = __str__
 
+    def __getitem__(self, node: Node) -> Fragment:
+        return _create_fragment(node)
+
+
+def _create_fragment(node: Node) -> Fragment:
+    instance = Fragment.__new__(Fragment)
+    instance._allow_init = True  # type: ignore
+    instance.__init__(node)  # type: ignore
+    return instance
+
+
+fragment = _create_fragment(None)
+
 
 def render_node(node: Node) -> _Markup:
     return _Markup("".join(iter_node(node)))
 
 
 def comment(text: str) -> Fragment:
     escaped_text = text.replace("--", "")
-    return Fragment(_Markup(f"<!-- {escaped_text} -->"))
+    return fragment[_Markup(f"<!-- {escaped_text} -->")]
 
 
 @t.runtime_checkable

tests/test_context.py

@@ -5,7 +5,7 @@
 import markupsafe
 import pytest
 
-from htpy import Context, Fragment, Node, div
+from htpy import Context, Node, div, fragment
 
 if t.TYPE_CHECKING:
     from .conftest import RenderFixture
@@ -116,6 +116,6 @@ def test_context_passed_via_fragment(render: RenderFixture) -> None:
     def echo(value: str) -> str:
         return value
 
-    result = div[ctx.provider("foo", Fragment(echo()))]
+    result = div[ctx.provider("foo", fragment[echo()])]
 
     assert render(result) == ["<div>", "foo", "</div>"]

tests/test_fragment.py

@@ -1,16 +1,17 @@
 import markupsafe
+import pytest
 
-from htpy import Fragment, i, p
+from htpy import Fragment, fragment, i, p
 
 from .conftest import RenderFixture
 
 
 def test_render_direct() -> None:
-    assert str(Fragment("Hello ", None, i["World"])) == "Hello <i>World</i>"
+    assert str(fragment["Hello ", None, i["World"]]) == "Hello <i>World</i>"
 
 
 def test_render_as_child(render: RenderFixture) -> None:
-    assert render(p["Say: ", Fragment("Hello ", None, i["World"]), "!"]) == [
+    assert render(p["Say: ", fragment["Hello ", None, i["World"]], "!"]) == [
         "<p>",
         "Say: ",
         "Hello ",
@@ -22,12 +23,16 @@ def test_render_as_child(render: RenderFixture) -> None:
     ]
 
 
+def test_plain_fragment(render: RenderFixture) -> None:
+    assert render(fragment) == []
+
+
 def test_render_nested(render: RenderFixture) -> None:
-    assert render(Fragment(Fragment("Hel", "lo "), "World")) == ["Hel", "lo ", "World"]
+    assert render(fragment[fragment["Hel", "lo "], "World"]) == ["Hel", "lo ", "World"]
 
 
 def test_render_chunks(render: RenderFixture) -> None:
-    assert render(Fragment("Hello ", None, i["World"])) == [
+    assert render(fragment["Hello ", None, i["World"]]) == [
         "Hello ",
         "<i>",
         "World",
@@ -36,8 +41,15 @@ def test_render_chunks(render: RenderFixture) -> None:
 
 
 def test_safe() -> None:
-    assert markupsafe.escape(Fragment(i["hi"])) == "<i>hi</i>"
+    assert markupsafe.escape(fragment[i["hi"]]) == "<i>hi</i>"
 
 
 def test_iter() -> None:
-    assert list(Fragment("Hello ", None, i["World"])) == ["Hello ", "<i>", "World", "</i>"]
+    assert list(fragment["Hello ", None, i["World"]]) == ["Hello ", "<i>", "World", "</i>"]
+
+
+def test_direct_init_typeerror() -> None:
+    with pytest.raises(
+        TypeError, match=r"Cannot instantiate Fragment directly\. Use fragment\[x\] instead"
+    ):
+        Fragment(None)