[BUG]: textual[syntax] does not install tree-sitter on Python 3.9 and syntax highlighting silently does not work

[Kalebe16]

Summary

On Python 3.9, installing textual[syntax] does not install tree-sitter, and syntax highlighting in TextArea.code_editor(...) does not work.

There is no error — it simply falls back to plain text without highlighting.

If I manually install tree-sitter, I then get:

RuntimeError: SyntaxAwareDocument unavailable - tree-sitter is not installed.

Steps to reproduce

python3.9 -m venv venv
source venv/bin/activate
pip install textual==8.0 "textual[syntax]"

from textual.app import App, ComposeResult
from textual.widgets import TextArea

class Demo(App):
    def compose(self) -> ComposeResult:
        yield TextArea.code_editor(
            '{ "a": 1 }',
            language="json",
            theme="monokai",
        )

Demo().run()

Environment

• python-3.9
• textual-8.0
• Os (ubuntu)

[github-actions]

We found the following entries in the FAQ which you may find helpful:

• How can I select and copy text in a Textual app?
• Why do some key combinations never make it to my app?
• How can I set a translucent app background?
• Why doesn't Textual support ANSI themes?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This project is developed and maintained by Will McGugan. Consider sponsoring Will's work on this project (and others).

This is an automated reply, generated by FAQtory

[TomJGooding]

Textual requires tree-sitter >= 0.25.0 which dropped support for Python 3.9.

The TextArea falls back to plain text by design, rather than crashing programs where tree-sitter can't be installed.

[Kalebe16]

Thanks for the clarification!

Would it make sense to document that syntax highlighting requires Python >= 3.10?

[github-actions]

I hope I solved your issue!

Consider sponsoring my work to continue to maintain and develop Textual.

• Will McGugan