Set classes (#2160)

* Setting classes

* changelog

* docstrings

* test bad identifiers

* Update CHANGELOG.md

Co-authored-by: Dave Pearson <davep@davep.org>

* Add return of self

---------

Co-authored-by: Dave Pearson <davep@davep.org>

tests/test_dom.py

@@ -45,6 +45,39 @@ def test_validate():
         node.toggle_class("1")
 
 
+def test_classes_setter():
+    node = DOMNode(classes="foo bar")
+    assert node.classes == frozenset({"foo", "bar"})
+    node.classes = "baz egg"
+    assert node.classes == frozenset({"baz", "egg"})
+    node.classes = ""
+    assert node.classes == frozenset({})
+
+
+def test_classes_setter_iterable():
+    node = DOMNode(classes="foo bar")
+    assert node.classes == frozenset({"foo", "bar"})
+    node.classes = "baz", "egg"
+    assert node.classes == frozenset({"baz", "egg"})
+    node.classes = []
+    assert node.classes == frozenset({})
+
+
+def test_classes_set_classes():
+    node = DOMNode(classes="foo bar")
+    assert node.classes == frozenset({"foo", "bar"})
+    node.set_classes("baz egg")
+    assert node.classes == frozenset({"baz", "egg"})
+    node.set_classes([])
+    assert node.classes == frozenset({})
+    node.set_classes(["paul"])
+    assert node.classes == frozenset({"paul"})
+    with pytest.raises(BadIdentifier):
+        node.classes = "foo 25"
+    with pytest.raises(BadIdentifier):
+        node.classes = ["foo", "25"]
+
+
 def test_inherited_bindings():
     """Test if binding merging is done correctly when (not) inheriting bindings."""
 

tests/test_query.py

@@ -152,6 +152,25 @@ def test_query_classes():
     # Now, let's check there are *no* children with the test class.
     assert len(app.query(".test")) == 0
 
+    # Add classes via set_classes
+    app.query(ClassTest).set_classes("foo bar")
+    assert (len(app.query(".foo"))) == CHILD_COUNT
+    assert (len(app.query(".bar"))) == CHILD_COUNT
+
+    # Reset classes
+    app.query(ClassTest).set_classes("")
+    assert (len(app.query(".foo"))) == 0
+    assert (len(app.query(".bar"))) == 0
+
+    # Repeat, to check setting empty iterable
+    app.query(ClassTest).set_classes("foo bar")
+    assert (len(app.query(".foo"))) == CHILD_COUNT
+    assert (len(app.query(".bar"))) == CHILD_COUNT
+
+    app.query(ClassTest).set_classes([])
+    assert (len(app.query(".foo"))) == 0
+    assert (len(app.query(".bar"))) == 0
+
     # Add the test class to everything and then check again.
     app.query(ClassTest).add_class("test")
     assert len(app.query(".test")) == CHILD_COUNT