The added unescape function unescapes escape sequences, transforming them back to their represented characters. The following escape sequences are supported:

• Standard C escape sequences:

  • \n for newline (LF)
  • \t for horizontal tab (HT)
  • \r for carriage return (CR)
  • \b for backspace (BS)
  • \f for formfeed (FF)
  • \v for vertical tab (VT)
  • \' for single quote (')
  • \" for double quote (")
  • \\ for backslash ()
  • \? for question mark (?)
  • \a for alert (bell, BEL)

• Hexadecimal escape codes:

  • \xH... where H... is one or more hexadecimal digits (0-9, A-F, a-f), allowing for the encoding of arbitrary utf32 characters.

If an escape sequence is not recognized, or if the hexadecimal escape does not form a valid Unicode character, the function generates an exception.

Fixes:
#12460
https://emqx.atlassian.net/browse/EMQX-11847

Release version: v/e5.?

Summary

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• [] Added property-based tests for code which performs user input validation
• Changed lines covered in coverage report
• Change log has been added to changes/(ce|ee)/(feat|perf|fix|breaking)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• Created PR to emqx-docs if documentation update is required, or link to a follow-up jira ticket
• [] Schema changes are backward compatible