mmm-mode crashes on gitit doc

[conal]

The following Markdown doc crashes mmm-mode breaks mmm-mode:

---
title: gitit doc
...


```
ham
```

More than three hyphens below, and mmm-mode crashes.

----

Note that in gitit pages, meta-data blocks end with three dots, not three hyphens.

The crash happens even when no mmm classes are added. In the scratch buffer:

mmm-classes-alist
((universal :front "{%\\([a-zA-Z-]+\\)%}" :back "{%/~1%}" :insert ((47 universal "Submode: " @ "{%" str "%}" @ "
" _ "
" @ "{%/" str "%}" @)) :match-submode mmm-univ-get-mode :save-matches 1))

I got mmm-mode version 0.5.4 from MELPA within the last few days.

Backtrace:

Debugger entered--Lisp error: (wrong-type-argument integer-or-marker-p nil)
  markdown-match-inline-generic("\\(?:\\`\\|[^\\]\\)\\(\\(`+\\)\\(\\(?:.\\|\n[^\n]\\)*?[^`]\\)\\(\\2\\)\\)\\(?:[^`]\\|\\'\\)" 145)
  markdown-match-code(145)
  font-lock-fontify-keywords-region(1 145 nil)
  font-lock-default-fontify-region(1 145 nil)
  font-lock-fontify-region(1 145 nil)
  byte-code("\212\303 �\304\216\305ed   #\210\306 \210\307\211�+\207" [save-match-data-internal verbose font-lock-fontified match-data ((byte-code "\301�\302\"\207" [save-match-data-internal set-match-data evaporate] 3)) font-lock-fontify-region font-lock-after-fontify-buffer t] 4)
  font-lock-default-fontify-buffer()
  font-lock-fontify-buffer()
  font-lock-initial-fontify()
  font-lock-mode(1)
  font-lock-refresh-defaults()
  markdown-reload-extensions()
  markdown-mode()
  mmm-update-mode-info(markdown-mode)
  mmm-mode-on()
  mmm-mode(nil)
  call-interactively(mmm-mode record nil)
  command-execute(mmm-mode record)
  execute-extended-command(nil "mmm-mode")
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)

[dgutov]

Hi! Sorry for the late reply.

The problem here seems to be than markdown-get-enclosing-fenced-block-construct returns a list where the second element is nil. This expression:

(save-match-data
 (set-match-data (markdown-text-property-at-point 'markdown-yaml-metadata-begin))
 (markdown-get-fenced-block-from-start 'markdown-yaml-metadata-begin))

returns (1 98) when you have 3 dashes at the end, and (1 nil) when you have four dashes. markdown-match-inline-generic uses the result with goto-char and fails as above.

Not sure why this is not a problem without mmm-mode, though. Maybe ask the maintainer of markdown-mode?

[conal]

Thanks very much for the help, and sorry that I incorrectly flagged it as an mmm-mode issue. I'll take it up with the markdown-mode maintainer as you suggested.

[dgutov]

Thanks very much for the help, and sorry that I incorrectly flagged it as an mmm-mode issue.

There's probably something we could be doing better in mmm-mode, but it'll take more in-depth knowledge to determine what.

I'll take it up with the markdown-mode maintainer as you suggested.

Thanks!