markup parse and tests

Author: willmcgugan

src/textual/content.py

@@ -271,6 +271,7 @@ def styled(
         return new_content
 
     def __eq__(self, other: object) -> bool:
+        """Compares text only, so that markup doesn't effect sorting."""
         if isinstance(other, str):
             return self.plain == other
         elif isinstance(other, Content):
@@ -284,6 +285,25 @@ def __lt__(self, other: object) -> bool:
             return self.plain < other.plain
         return NotImplemented
 
+    def is_same(self, content: Content) -> bool:
+        """Compare to another Content object.
+
+        Two Content objects are the same if their text and spans match.
+        Note that if you use the `==` operator to compare Content instances, it will only consider the plain text.
+
+
+        Args:
+            content: Content instance.
+
+        Returns:
+            `True` if this is identical to `content`, otherwise False
+        """
+        if self is content:
+            return True
+        if self.plain != content.plain:
+            return False
+        return self.spans == content.spans
+
     def get_optimal_width(
         self,
         rules: RulesMap,

src/textual/css/tokenizer.py

@@ -283,7 +283,7 @@ def get_token(self, expect: Expect) -> Token:
             match = expect.match(line, col_no)
 
         if match is None:
-            error_line = line[col_no:].rstrip()
+            error_line = line[col_no:]
             error_message = (
                 f"{expect.description} (found {error_line.split(';')[0]!r})."
             )