Image `alt` text loses backslash escapes

[kdeldycke]

What version of myst-parser are you using?

5.1.0

What version dependencies are you using?

• markdown-it-py 4.2.0
• docutils 0.22.4
• Python 3.14.7

What operating system are you using?

Mac

Describe the Bug

The alt attribute of an image loses every backslash escape and every entity of its alt text: ![C:\Python26](x.png) gives alt="C:ython26".

renderInlineAsText reads text tokens only. An escape or an entity inside an image is a text_special token with no children:

MyST-Parser/myst_parser/mdit_to_docutils/base.py

Lines 453 to 468 in 2871eb9

	def renderInlineAsText(self, tokens: list[SyntaxTreeNode]) -> str: # noqa: N802
	"""Special kludge for image `alt` attributes to conform CommonMark spec.
	Don't try to use it! Spec requires to show `alt` content with stripped markup,
	instead of simple escaping.
	"""
	result = ""
	for token in tokens or []:
	if token.type == "text":
	result += token.content
	# elif token.type == "image":
	# result += self.renderInlineAsText(token.children)
	else:
	result += self.renderInlineAsText(token.children or [])
	return result

markdown-it 15.0.0 fixed the token side: markdown-it/markdown-it@974e2d7 makes text_join convert those tokens to text inside image alt text. markdown-it-py 4.2.0 does not have that change.

Expected Behavior

alt="a * b", alt="a & b" and alt="C:\Python26".

To Reproduce

from docutils.core import publish_parts
from myst_parser.parsers.docutils_ import Parser

for src in (
    r"![a \* b](x.png)",
    "![a & b](x.png)",
    r"![C:\Python26](x.png)",
    r"[a \* b & c](https://example.com)",
):
    print(publish_parts(src, parser=Parser(), writer_name="html5")["body"], end="")

Output:

<p><img alt="a  b" src="x.png" /></p>
<p><img alt="a  b" src="x.png" /></p>
<p><img alt="C:ython26" src="x.png" /></p>
<p><a class="reference external" href="https://example.com">a * b &amp; c</a></p>

[kdeldycke]

This is related to:

• Backslash escapes and entities are deleted from image alt text hukkin/mdformat#599
• Image alt text loses backslash escapes and entities markdown-it-py#445