[0] is being considered a markup tag

[kuhnchris]

Have you checked closed issues? (https://github.com/Textualize/textual/issues?q=is%3Aissue+is%3Aclosed) Yes

Have you checked against the most recent version of Textual? (https://pypi.org/search/?q=textual) Yes

The bug

• Trying to create a Static with markup=True with predefined text "[0] Hello World".
  => Crash

• Trying to escape the text results in a non-escaped string.
  => Crash

According to McGugan:

[0] shouldn't be considered a tag and shouldn't need escaping. If it is throwing a markup error, that is a bug. Please file an issue.

Error:

MarkupError: Expected markup style value (found '0] Hello World!').

MRE:

from textual.app import App
from textual.widgets import Footer, Static
from textual.markup import escape
class TextualApp(App):

    DEFAULT_CSS = """
    /* any needed CSS  here */
    """

    def compose(self):
        yield Static(escape("[0] Hello World!"))
        yield Footer()

    # code that causes a bug here

textual diagnose:

<!-- This is valid Markdown, please paste the following directly in to a GitHub issue -->
# Textual Diagnostics

## Versions

| Name    | Value  |
|---------|--------|
| Textual | 3.1.1  |
| Rich    | 14.0.0 |

## Python

| Name           | Value                                |
|----------------|--------------------------------------|
| Version        | 3.12.9                               |
| Implementation | CPython                              |
| Compiler       | GCC 13.2.1 20240309                  |
| Executable     | /home/kuhnchris/test/venv/bin/python |

## Operating System

| Name    | Value                                             |
|---------|---------------------------------------------------|
| System  | Linux                                             |
| Release | 6.12.21-0-lts                                     |
| Version | #1-Alpine SMP PREEMPT_DYNAMIC 2025-04-01 11:09:17 |

## Terminal

| Name                 | Value          |
|----------------------|----------------|
| Terminal Application | *Unknown*      |
| TERM                 | xterm-256color |
| COLORTERM            | truecolor      |
| FORCE_COLOR          | *Not set*      |
| NO_COLOR             | *Not set*      |

## Rich Console options

| Name           | Value                |
|----------------|----------------------|
| size           | width=289, height=98 |
| legacy_windows | False                |
| min_width      | 1                    |
| max_width      | 289                  |
| is_terminal    | True                 |
| encoding       | utf-8                |
| max_height     | 98                   |
| justify        | None                 |
| overflow       | None                 |
| no_wrap        | False                |
| highlight      | None                 |
| markup         | None                 |
| height         | None                 |

Technical workaround:
(by David Fokkema)

import re

escape("[1]", _escape=re.compile(r"(\\*)(\[[a-z0-9#/@][^[]*?])").sub)

(by kuhnchris)

outputText.replace("[", "\\[")

Full Stack log (textual run --dev):

fullStackTrace.txt

[github-actions]

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

• Does Textual support images?
• Why doesn't Textual look good on macOS?

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

This is an automated reply, generated by FAQtory

[python-and-novella]

The uppercase also should be considered:

from textual.app import App
from textual.widgets import Static
from textual.markup import escape
import re

class MyApp(App):
    def on_mount(self):
        self.widgets = [ 
                Static(escape('[0 W] Hello World!',re.compile(r'(\\*)(\[[0-9a-zA-Z#/@][^[]*?])').sub)),
            ]
        self.mount_all(self.widgets)

if __name__ == '__main__':
    app = MyApp()
    app.run()