filling block comments produces "unexpected end of comment block" error

[holtzermann17]

I open a new mode Lean buffer and put in contents as follows:

/- xxx xxxx xx.xxxxx xx xxxx xx xxxxxx xxx xxxxxxxxx xxxxxxxxx xxxxx, xxxxx xxxxx xxx xxxx xxxxxxxx xxxxxxxxxxxxx. -/

Then push M-q with the cursor anywhere on that line. I get:

/- xxx xxxx xx.xxxxx xx xxxx xx xxxxxx xxx xxxxxxxxx xxxxxxxxx xxxxx,
/- xxxxx xxxxx xxx xxxx xxxxxxxx xxxxxxxxxxxxx. -/

Flycheck now notices an error, unexpected end of comment block (lean-checker) (details via M-x flycheck-list-errors on the second line).

---

This behaviour could be improved, though I'm not immediately sure what the programming solution is, the expected output would be

/- xxx xxxx xx.xxxxx xx xxxx xx xxxxxx xxx xxxxxxxxx xxxxxxxxx xxxxx,
   xxxxx xxxxx xxx xxxx xxxxxxxx xxxxxxxxxxxxx. -/

[holtzermann17]

It looks like this is the relevant documentation page:
https://www.gnu.org/software/emacs/manual/html_node/emacs/Adaptive-Fill.html#Adaptive-Fill

You can specify more complex ways of choosing a fill prefix automatically by setting the variable adaptive-fill-function to a function.

[holtzermann17]

Well, this solves it without writing any code.

M-x package-install RET filladapt RET

(require 'filladapt)
(add-hook 'lean-mode-hook #'filladapt-mode)

[holtzermann17]

Actually, this is also needed:

(setq filladapt-token-table
      '(("^" beginning-of-line)
        (">+" citation->)
        ("\\(\\w\\|[0-9]\\)[^'`\"< 	
]*>[ 	]*" supercite-citation)
        (";+" lisp-comment)
        ;; Added this line
        ("--" lisp-comment)
        ("#+" sh-comment)
        ("%+" postscript-comment)
        ("///*" c++-comment)
        ("@c[ 	]" texinfo-comment)
        ("@comment[ 	]" texinfo-comment)
        ("\\\\item[ 	]" bullet)
        ("[0-9]+\\.[ 	]" bullet)
        ("[0-9]+\\(\\.[0-9]+\\)+[ 	]" bullet)
        ("[A-Za-z]\\.[ 	]" bullet)
        ("(?[0-9]+)[ 	]" bullet)
        ("(?[A-Za-z])[ 	]" bullet)
        ("[0-9]+[A-Za-z]\\.[ 	]" bullet)
        ("(?[0-9]+[A-Za-z])[ 	]" bullet)
        ("[-~*+]+[ 	]" bullet)
        ("o[ 	]" bullet)
        ("[ 	]+" space)
        ("$" end-of-line)))