Merge branch 'css' into scroll-view

src/textual/css/stylesheet.py

@@ -285,7 +285,7 @@ class Stylesheet:
         _check_rule = self._check_rule
 
         # Collect the rules defined in the stylesheet
-        for rule in self.rules:
+        for rule in reversed(self.rules):
             for specificity in _check_rule(rule, node):
                 for key, rule_specificity, value in rule.styles.extract_rules(
                     specificity
@@ -301,6 +301,7 @@ class Stylesheet:
                 for name, specificity_rules in rule_attributes.items()
             },
         )
+
         self.replace_rules(node, node_rules, animate=animate)
 
         node.component_styles.clear()

src/textual/widgets/__init__.py

@@ -1,23 +1,42 @@
-from ._datatable import DataTable
+from __future__ import annotations
-from ._footer import Footer
+from importlib import import_module
-from ._header import Header
+import typing
-from ._button import Button
-from ._placeholder import Placeholder
-from ._static import Static
-from ._tree_control import TreeControl, TreeClick, TreeNode, NodeID
-from ._directory_tree import DirectoryTree, FileClick
 
+from ..case import camel_to_snake
+
+if typing.TYPE_CHECKING:
+    from ..widget import Widget
+
+
+# ⚠️For any new built-in Widget we create, not only we have to add them to the following list, but also to the
+# `__init__.pyi` file in this same folder - otherwise text editors and type checkers won't be able to "see" them.
 __all__ = [
     "Button",
     "DataTable",
     "DirectoryTree",
-    "FileClick",
     "Footer",
     "Header",
     "Placeholder",
     "Static",
-    "TreeClick",
     "TreeControl",
-    "TreeNode",
-    "NodeID",
 ]
+
+
+_WIDGETS_LAZY_LOADING_CACHE: dict[str, type[Widget]] = {}
+
+# Let's decrease startup time by lazy loading our Widgets:
+def __getattr__(widget_class: str) -> type[Widget]:
+    try:
+        return _WIDGETS_LAZY_LOADING_CACHE[widget_class]
+    except KeyError:
+        pass
+
+    if widget_class not in __all__:
+        raise ImportError(f"Package 'textual.widgets' has no class '{widget_class}'")
+
+    widget_module_path = f"._{camel_to_snake(widget_class)}"
+    module = import_module(widget_module_path, package="textual.widgets")
+    class_ = getattr(module, widget_class)
+
+    _WIDGETS_LAZY_LOADING_CACHE[widget_class] = class_
+    return class_

src/textual/widgets/__init__.pyi

@@ -0,0 +1,8 @@
+# This stub file must re-export every classes exposed in the __init__.py's `__all__` list:
+from ._button import Button as Button
+from ._directory_tree import DirectoryTree as DirectoryTree
+from ._footer import Footer as Footer
+from ._header import Header as Header
+from ._placeholder import Placeholder as Placeholder
+from ._static import Static as Static
+from ._tree_control import TreeControl as TreeControl

tests/css/test_stylesheet.py

@@ -7,6 +7,98 @@ from textual.color import Color
 from textual.css._help_renderables import HelpText
 from textual.css.stylesheet import Stylesheet, StylesheetParseError
 from textual.css.tokenizer import TokenizeError
+from textual.dom import DOMNode
+from textual.geometry import Spacing
+
+
+def _make_stylesheet(css: str) -> Stylesheet:
+    stylesheet = Stylesheet()
+    stylesheet.source["test.css"] = css
+    stylesheet.parse()
+    return stylesheet
+
+
+def test_stylesheet_apply_highest_specificity_wins():
+    """#ids have higher specificity than .classes"""
+    css = "#id {color: red;} .class {color: blue;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(classes="class", id="id")
+    stylesheet.apply(node)
+
+    assert node.styles.color == Color(255, 0, 0)
+
+
+def test_stylesheet_apply_doesnt_override_defaults():
+    css = "#id {color: red;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(id="id")
+    stylesheet.apply(node)
+
+    assert node.styles.margin == Spacing.all(0)
+    assert node.styles.box_sizing == "border-box"
+
+
+def test_stylesheet_apply_highest_specificity_wins_multiple_classes():
+    """When we use two selectors containing only classes, then the selector
+    `.b.c` has greater specificity than the selector `.a`"""
+    css = ".b.c {background: blue;} .a {background: red; color: lime;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(classes="a b c")
+    stylesheet.apply(node)
+
+    assert node.styles.background == Color(0, 0, 255)
+    assert node.styles.color == Color(0, 255, 0)
+
+
+def test_stylesheet_many_classes_dont_overrule_id():
+    """#id is further to the left in the specificity tuple than class, and
+    a selector containing multiple classes cannot take priority over even a
+    single class."""
+    css = "#id {color: red;} .a.b.c.d {color: blue;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(classes="a b c d", id="id")
+    stylesheet.apply(node)
+
+    assert node.styles.color == Color(255, 0, 0)
+
+
+def test_stylesheet_last_rule_wins_when_same_rule_twice_in_one_ruleset():
+    css = "#id {color: red; color: blue;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(id="id")
+    stylesheet.apply(node)
+
+    assert node.styles.color == Color(0, 0, 255)
+
+
+def test_stylesheet_rulesets_merged_for_duplicate_selectors():
+    css = "#id {color: red; background: lime;} #id {color:blue;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(id="id")
+    stylesheet.apply(node)
+
+    assert node.styles.color == Color(0, 0, 255)
+    assert node.styles.background == Color(0, 255, 0)
+
+
+def test_stylesheet_apply_takes_final_rule_in_specificity_clash():
+    """.a and .b both contain background and have same specificity, so .b wins
+    since it was declared last - the background should be blue."""
+    css = ".a {background: red; color: lime;} .b {background: blue;}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(classes="a b", id="c")
+    stylesheet.apply(node)
+
+    assert node.styles.color == Color(0, 255, 0)  # color: lime
+    assert node.styles.background == Color(0, 0, 255)  # background: blue
+
+
+def test_stylesheet_apply_empty_rulesets():
+    """Ensure that we don't crash when working with empty rulesets"""
+    css = ".a {} .b {}"
+    stylesheet = _make_stylesheet(css)
+    node = DOMNode(classes="a b")
+    stylesheet.apply(node)
 
 
 @pytest.mark.parametrize(