fix: strip illegal XML chars from rendered output#653
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Add XML 1.0 illegal-character sanitization to template rendering and core property rendering so control/noncharacter code points injected via context values no longer break DOCX XML parsing. The change uses a regex-based fast path and preserves valid XML whitespace controls. Also adds a regression test template/script covering body text, escaped content, header/footer, and core properties.
Update the illegal XML character regex to better match XML 1.0 constraints by covering the full DEL/C1 control range (`\x7f-\x9f`) and excluding UTF-16 surrogate code points (`\ud800-\udfff`). This prevents invalid characters from leaking into generated document XML.
fix: strip illegal XML chars from rendered output
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This pull request improves the robustness of XML output by ensuring that any XML-1.0-illegal characters injected through context values are stripped from rendered output. This prevents document corruption due to invalid XML characters and adds a test to verify this behavior.
XML character sanitization:
_ILLEGAL_XML_CHARS_REand a helper function_strip_illegal_xml_charsto remove illegal XML-1.0 characters from rendered output, mirroring the approach used in other libraries like openpyxl._strip_illegal_xml_charsinrender_xml_partandrender_propertiesto sanitize all rendered XML strings and core properties before they are parsed or written, preventing any single bad character from corrupting the output.Testing:
tests/illegal_xml_chars.pyto verify that XML-1.0-illegal characters injected through context values are correctly stripped from all relevant parts of the document.