Allow conditional rendering based on bool.

Technically this commit just avoids rendering True and False. It allows
for using short-circuiting `and` for conditional rendering.

docs/usage.md

@@ -43,9 +43,13 @@ and safe to directly insert variable data via f-strings:
 
 ### Conditional Rendering
 
-`None` will not render anything. This can be useful to conditionally render some content.
+`True`, `False` and `None` will not render anything. Python's `and` and `or`
+operators will
+[short-circuit](https://docs.python.org/3/library/stdtypes.html#boolean-operations-and-or-not).
+You can use this to conditionally render content with inline `and` and
+`or`.
 
-```pycon title="Conditional rendering"
+```pycon title="Conditional rendering with a value that may be None"
 
 >>> from htpy import div, b
 >>> error = None
@@ -55,14 +59,33 @@ and safe to directly insert variable data via f-strings:
 <div></div>
 
 >>> error = 'Enter a valid email address.'
->>> print(div[error and b[error]])
+>>> print(div[has_error and b[error_message]])
 <div><b>Enter a valid email address.</b></div>
 
 # Inline if/else can also be used:
 >>> print(div[b[error] if error else None])
 <div><b>Enter a valid email address.</b></div>
 ```
 
+```pycon title="Conditional rendering based on a bool variable"
+>>> from htpy import div
+>>> is_happy = True
+>>> print(div[is_happy and "😄"])
+<div>😄</div>
+
+>>> is_sad = False
+>>> print(div[is_sad and "😔"])
+<div></div>
+
+>>> is_allowed = True
+>>> print(div[is_allowed or "Access denied!"])
+<div></div>
+
+>>> is_allowed = False
+>>> print(div[is_allowed or "Access denied!"])
+<div>Access denied</div>
+```
+
 ### Loops / Iterating Over Children
 
 You can pass a list, tuple or generator to generate multiple children:

htpy/__init__.py

@@ -110,6 +110,12 @@ def iter_node(x: Node) -> Iterator[str]:
     if x is None:
         return
 
+    if x is True:
+        return
+
+    if x is False:
+        return
+
     if isinstance(x, BaseElement):
         yield from x
     elif isinstance(x, str) or hasattr(x, "__html__"):
@@ -227,7 +233,9 @@ def __html__(self) -> str: ...
 
 _ClassNamesDict: TypeAlias = dict[str, bool]
 _ClassNames: TypeAlias = Iterable[str | None | bool | _ClassNamesDict] | _ClassNamesDict
-Node: TypeAlias = None | str | BaseElement | _HasHtml | Iterable["Node"] | Callable[[], "Node"]
+Node: TypeAlias = (
+    None | bool | str | BaseElement | _HasHtml | Iterable["Node"] | Callable[[], "Node"]
+)
 
 Attribute: TypeAlias = None | bool | str | _HasHtml | _ClassNames
 

tests/test_children.py

@@ -104,8 +104,9 @@ def test_custom_element() -> None:
     assert str(el) == "<my-custom-element></my-custom-element>"
 
 
-def test_ignore_none() -> None:
-    assert str(div[None]) == "<div></div>"
+@pytest.mark.parametrize("ignored_value", [None, True, False])
+def test_ignored(ignored_value: Any) -> None:
+    assert str(div[ignored_value]) == "<div></div>"
 
 
 def test_iter() -> None:
@@ -197,7 +198,7 @@ def test_callable_in_generator() -> None:
     assert str(div[((lambda: "hi") for _ in range(1))]) == "<div>hi</div>"
 
 
-@pytest.mark.parametrize("not_a_child", [1234, True, False, b"foo", object(), object])
+@pytest.mark.parametrize("not_a_child", [1234, b"foo", object(), object, 1, 0])
 def test_invalid_child(not_a_child: Any) -> None:
     with pytest.raises(ValueError, match="is not a valid child element"):
         str(div[not_a_child])