fix css reload

sandbox/uber.css

@@ -1,7 +1,7 @@
 #uber1 {
   layout: vertical;
 
-  background: dark_green;
+  background: green;
   overflow: hidden auto;
   border: heavy white;
 }

sandbox/uber.py

@@ -37,7 +37,7 @@ class BasicApp(App):
         await self.dispatch_key(event)
 
     def action_quit(self):
-        self.panic(self.screen.tree)
+        self.panic(self.app.tree)
 
     def action_dump(self):
         self.panic(str(self.app.registry))

src/textual/app.py

@@ -330,10 +330,10 @@ class App(Generic[ReturnType], DOMNode):
     async def _on_css_change(self) -> None:
         """Called when the CSS changes (if watch_css is True)."""
         if self.css_file is not None:
-            stylesheet = Stylesheet(variables=self.get_css_variables())
+
             try:
                 time = perf_counter()
-                stylesheet.read(self.css_file)
+                self.stylesheet.read(self.css_file)
                 elapsed = (perf_counter() - time) * 1000
                 self.log(f"loaded {self.css_file} in {elapsed:.0f}ms")
             except Exception as error:
@@ -342,7 +342,6 @@ class App(Generic[ReturnType], DOMNode):
                 self.log(error)
             else:
                 self.reset_styles()
-                self.stylesheet = stylesheet
                 self.stylesheet.update(self)
                 self.screen.refresh(layout=True)
 
@@ -506,7 +505,9 @@ class App(Generic[ReturnType], DOMNode):
             if self.css_file is not None:
                 self.stylesheet.read(self.css_file)
             if self.css is not None:
-                self.stylesheet.parse(self.css, path=f"<{self.__class__.__name__}>")
+                self.stylesheet.add_source(
+                    self.css, path=f"<{self.__class__.__name__}>"
+                )
         except Exception as error:
             self.on_exception(error)
             self._print_error_renderables()

src/textual/css/parse.py

@@ -340,7 +340,7 @@ if __name__ == "__main__":
     console = Console()
     stylesheet = Stylesheet()
     try:
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
     except StylesheetParseError as e:
         console.print(e.errors)
     print(stylesheet)

src/textual/css/stylesheet.py

@@ -101,21 +101,23 @@ class StylesheetErrors:
 @rich.repr.auto
 class Stylesheet:
     def __init__(self, *, variables: dict[str, str] | None = None) -> None:
-        self.rules: list[RuleSet] = []
+        self._rules: list[RuleSet] | None = None
         self.variables = variables or {}
-        self.source: list[tuple[str, str]] = []
+        self.source: dict[str, str] = {}
 
     def __rich_repr__(self) -> rich.repr.Result:
         yield self.rules
 
     @property
-    def css(self) -> str:
-        return "\n\n".join(rule_set.css for rule_set in self.rules)
+    def rules(self) -> list[RuleSet]:
+        if self._rules is None:
+            self.parse()
+        assert self._rules is not None
+        return self._rules
 
     @property
-    def any_errors(self) -> bool:
-        """Check if there are any errors."""
-        return any(rule.errors for rule in self.rules)
+    def css(self) -> str:
+        return "\n\n".join(rule_set.css for rule_set in self.rules)
 
     @property
     def error_renderable(self) -> StylesheetErrors:
@@ -129,6 +131,28 @@ class Stylesheet:
         """
         self.variables = variables
 
+    def _parse_rules(self, css: str, path: str) -> list[RuleSet]:
+        """Parse CSS and return rules.
+
+
+        Args:
+            css (str): String containing Textual CSS.
+            path (str): Path to CSS or unique identifier
+
+        Raises:
+            StylesheetError: If the CSS is invalid.
+
+        Returns:
+            list[RuleSet]: List of RuleSets.
+        """
+        try:
+            rules = list(parse(css, path, variables=self.variables))
+        except TokenizeError:
+            raise
+        except Exception as error:
+            raise StylesheetError(f"failed to parse css; {error}")
+        return rules
+
     def read(self, filename: str) -> None:
         """Read Textual CSS file.
 
@@ -146,19 +170,10 @@ class Stylesheet:
             path = os.path.abspath(filename)
         except Exception as error:
             raise StylesheetError(f"unable to read {filename!r}; {error}")
-        try:
-            rules = list(parse(css, path, variables=self.variables))
-        except TokenizeError:
-            raise
-        except Exception as error:
-            raise StylesheetError(f"failed to parse {filename!r}; {error!r}")
-        else:
-            self.source.append((css, path))
-        self.rules.extend(rules)
-        if self.any_errors:
-            raise StylesheetParseError(self.error_renderable)
+        self.source[path] = css
+        self._rules = None
 
-    def parse(self, css: str, *, path: str = "") -> None:
+    def add_source(self, css: str, path: str | None = None) -> None:
         """Parse CSS from a string.
 
         Args:
@@ -169,28 +184,30 @@ class Stylesheet:
             StylesheetError: If the CSS could not be read.
             StylesheetParseError: If the CSS is invalid.
         """
-        if (css, path) in self.source:
+
+        if path is None:
+            path = str(hash(css))
+        if path in self.source and self.source[path] == css:
+            # Path already in source, and CSS is identical
             return
-        try:
-            rules = list(parse(css, path, variables=self.variables))
-        except TokenizeError:
-            raise
-        except Exception as error:
-            raise StylesheetError(f"failed to parse css; {error}")
-        else:
-            self.source.append((css, path))
-        self.rules.extend(rules)
-        if self.any_errors:
-            raise StylesheetParseError(self.error_renderable)
 
-    def _clone(self, stylesheet: Stylesheet) -> None:
-        """Replace this stylesheet contents with another.
+        self.source[path] = css
+        self._rules = None
 
-        Args:
-            stylesheet (Stylesheet): A Stylesheet.
+    def parse(self) -> None:
+        """Parse the source in the stylesheet.
+
+        Raises:
+            StylesheetParseError: If there are any CSS related errors.
         """
-        self.rules = stylesheet.rules.copy()
-        self.source = stylesheet.source.copy()
+        rules: list[RuleSet] = []
+        add_rules = rules.extend
+        for path, css in self.source.items():
+            css_rules = self._parse_rules(css, path)
+            if any(rule.errors for rule in css_rules):
+                raise StylesheetParseError(self.error_renderable)
+            add_rules(css_rules)
+        self._rules = rules
 
     def reparse(self) -> None:
         """Re-parse source, applying new variables.
@@ -202,9 +219,10 @@ class Stylesheet:
         """
         # Do this in a fresh Stylesheet so if there are errors we don't break self.
         stylesheet = Stylesheet(variables=self.variables)
-        for css, path in self.source:
-            stylesheet.parse(css, path=path)
-        self._clone(stylesheet)
+        for path, css in self.source.items():
+            stylesheet.add_source(css, path)
+        self._rules = None
+        self.source = stylesheet.source
 
     @classmethod
     def _check_rule(cls, rule: RuleSet, node: DOMNode) -> Iterable[Specificity3]:
@@ -403,7 +421,7 @@ if __name__ == "__main__":
     """
 
     stylesheet = Stylesheet()
-    stylesheet.parse(CSS)
+    stylesheet.add_source(CSS)
 
     print(stylesheet.css)
 

src/textual/widget.py

@@ -68,10 +68,6 @@ class Widget(DOMNode):
 
     can_focus: bool = False
 
-    DEFAULT_STYLES = """
-
-    """
-
     CSS = """
     """
 
@@ -127,7 +123,9 @@ class Widget(DOMNode):
             app (App): App instance.
         """
         # Parser the Widget's CSS
-        self.app.stylesheet.parse(self.CSS, path=f"<{self.__class__.__name__}>")
+        self.app.stylesheet.add_source(
+            self.CSS, f"{__file__}:<{self.__class__.__name__}>"
+        )
 
     def get_box_model(self, container: Size, viewport: Size) -> BoxModel:
         """Process the box model for this widget.

src/textual/widgets/_button.py

@@ -24,8 +24,8 @@ class Button(Widget, can_focus=True):
         color: $text-primary;
         content-align: center middle;
         border: tall $primary-lighten-3;                
-        margin: 1;
-        min-width:16;
+        
+        margin: 1 0;
         text-style: bold;
     }
 

tests/css/test_parse.py

@@ -864,7 +864,7 @@ class TestParseLayout:
         css = "#some-widget { layout: dock; }"
 
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
         assert isinstance(styles.layout, DockLayout)
@@ -874,7 +874,7 @@ class TestParseLayout:
 
         stylesheet = Stylesheet()
         with pytest.raises(StylesheetParseError) as ex:
-            stylesheet.parse(css)
+            stylesheet.add_source(css)
 
         assert ex.value.errors is not None
 
@@ -886,7 +886,7 @@ class TestParseText:
         }
         """
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
         assert styles.color == Color.parse("green")
@@ -897,7 +897,7 @@ class TestParseText:
         }
         """
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
         assert styles.background == Color.parse("red")
@@ -933,7 +933,7 @@ class TestParseOffset:
         }}
         """
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
 
@@ -972,7 +972,7 @@ class TestParseOffset:
         }}
         """
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
 
@@ -1002,7 +1002,7 @@ class TestParseTransition:
         }}
         """
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
 
@@ -1017,7 +1017,7 @@ class TestParseTransition:
     def test_no_delay_specified(self):
         css = f"#some-widget {{ transition: offset-x 1 in_out_cubic; }}"
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         styles = stylesheet.rules[0].styles
 
@@ -1032,7 +1032,7 @@ class TestParseTransition:
 
         stylesheet = Stylesheet()
         with pytest.raises(StylesheetParseError) as ex:
-            stylesheet.parse(css)
+            stylesheet.add_source(css)
 
         stylesheet_errors = stylesheet.rules[0].errors
 
@@ -1056,7 +1056,7 @@ class TestParseOpacity:
     def test_opacity_to_styles(self, css_value, styles_value):
         css = f"#some-widget {{ opacity: {css_value} }}"
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
         assert stylesheet.rules[0].styles.opacity == styles_value
         assert not stylesheet.rules[0].errors
@@ -1066,7 +1066,7 @@ class TestParseOpacity:
         stylesheet = Stylesheet()
 
         with pytest.raises(StylesheetParseError):
-            stylesheet.parse(css)
+            stylesheet.add_source(css)
         assert stylesheet.rules[0].errors
 
 
@@ -1074,7 +1074,7 @@ class TestParseMargin:
     def test_margin_partial(self):
         css = "#foo {margin: 1; margin-top: 2; margin-right: 3; margin-bottom: -1;}"
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
         assert stylesheet.rules[0].styles.margin == Spacing(2, 3, -1, 1)
 
 
@@ -1082,5 +1082,5 @@ class TestParsePadding:
     def test_padding_partial(self):
         css = "#foo {padding: 1; padding-top: 2; padding-right: 3; padding-bottom: -1;}"
         stylesheet = Stylesheet()
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
         assert stylesheet.rules[0].styles.padding == Spacing(2, 3, -1, 1)

tests/css/test_stylesheet.py

@@ -42,7 +42,7 @@ def test_color_property_parsing(css_value, expectation, expected_color):
     )
 
     with expectation:
-        stylesheet.parse(css)
+        stylesheet.add_source(css)
 
     if expected_color:
         css_rule = stylesheet.rules[0]