Fallback to text lexer when lexer not found

CHANGELOG.md

@@ -13,7 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- Add missing `end` keyword argument to `Text.from_markup`
+- Add missing `end` keyword argument to `Text.from_markup` https://github.com/Textualize/rich/pull/2095
+- Fallback to text lexer when no lexer guessed https://github.com/Textualize/rich/pull/2133
 - Fixed issue with decoding ANSI reset https://github.com/Textualize/rich/issues/2112
 
 ## [12.0.1] - 2022-03-22

rich/traceback.py

@@ -12,6 +12,7 @@
 from pygments.token import Comment, Keyword, Name, Number, Operator, String
 from pygments.token import Text as TextToken
 from pygments.token import Token
+from pygments.util import ClassNotFound
 
 from . import pretty
 from ._loop import loop_last
@@ -521,10 +522,10 @@ def _guess_lexer(cls, filename: str, code: str) -> str:
             first_line = code[:new_line_index] if new_line_index != -1 else code
             if first_line.startswith("#!") and "python" in first_line.lower():
                 return "python"
-        lexer_name = (
-            cls.LEXERS.get(ext) or guess_lexer_for_filename(filename, code).name
-        )
-        return lexer_name
+        try:
+            return cls.LEXERS.get(ext) or guess_lexer_for_filename(filename, code).name
+        except ClassNotFound:
+            return "text"
 
     @group()
     def _render_stack(self, stack: Stack) -> RenderResult:

tests/test_traceback.py

@@ -237,6 +237,16 @@ def test_guess_lexer():
     assert Traceback._guess_lexer("foo", "foo\nbnar") == "text"
 
 
+def test_guess_lexer_yaml_j2():
+    # https://github.com/Textualize/rich/issues/2018
+    code = """\
+foobar:
+    something: {{ raiser() }}
+    else: {{ 5 + 5 }}
+    """
+    assert Traceback._guess_lexer("test.yaml.j2", code) == "text"
+
+
 def test_recursive():
     def foo(n):
         return bar(n)