Why is autoheader crashing with web-mode?

Question

I got a situation here, that I couldn't get resolved with the maintainer of web-mode. So I'm asking here, if anyone knows a good suggestion.

Ok, what I have here: GNU Emacs GUI (version 24.4.51.1 (x86_64-w64-mingw32) compiled from Harroogan Emacs.) Packages web-mode and header2.el. If you need more detail about header2, see right answer here on StackExchange. It's a great package, I really recommend it.

Situation:

header2.el lets you define file headers for different types of file (C, shell, EmacsLisp, and so on). You can automatically insert a header when you open a new file buffer.

I ran into crashes, when I use web-mode in combination with header2.el. This is tested with an empty Emacs configuration (emacs -q).

When I use header2.el in combination with PHP-mode, JS-mode, and HTML-mode, I don't run into crashes and everything works fine.

Action:

First, you need to configure your emacs.d, in order to get the packages.

(setq user-emacs-directory "C:/Dropbox/Emacs/.emacs.d/")
(add-to-list 'load-path "C:\\Dropbox\\Emacs\\.emacs.d\\")

Then do load the packages Web-mode and header2.

(require 'header2)
(require 'web-mode) 

Then you need to configure the header, and set it up to be automatic created when create a new file:

(setq php-tag "<?php \n \n")
(setq html-close-tag " --> \n") 

(defsubst my/header-title ()
(insert
(if (eq major-mode 'php-mode)
php-tag
" \n")
(concat comment-start  " File " (buffer-name))
(if (eq major-mode 'web-mode)
html-close-tag
" \n")
"\n"))

(setq make-header-hook '(my/header-title))

(autoload 'auto-update-file-header "header2")
(add-hook 'write-file-hooks 'auto-update-file-header)

(autoload 'auto-make-header "header2")
(add-hook 'html-mode-hook 'auto-make-header) 
(add-hook 'web-mode-hook 'auto-make-header) 
(add-hook 'php-mode-hook 'auto-make-header) 
(add-hook 'js-mde-hook 'auto-make-header)  

Errornous behavior:

I create in Emacs a new file, called foobar.php. I get the header automatically inserted for me. And I can type around and press RET. Everything works fine. Same for foobar.js and foobar.html

Then I add (add-to-list 'auto-mode-alist '("\\.html\\'" . web-mode)) to my setup. This means that when I open a HTML file, Web-mode will be enabled as a major mode.

I restart Emacs. Then I create a new file, called foobar.html. The .html-filetype is hooked on web-mode. When typing some characters and press RET, this causes Emacs to freeze. Nothing is appearing in the *Messages*-buffer. This will not happen, when I don't add the .html extension to the Web-mode on auto-mode-alist, and get html-modeinstead.

Notice that autoheader is not a minor mode. It's a action hook, that insert the text when you enter a major mode. So I'm puzzled why it lets unrecoverrable crashing Emacs. It's a fairly simple package, after all.

Any suggestion would be appreciated.

Answer 1

I couldn't reproduce the crash, instead my development emacs just froze. However, it froze exactly when you said yours crashed, so I'll assume the problem is the same.

This is an infinite loop (i.e. bug) in web-mode-markup-indentation-origin. Here's is the basic run-down on what's going on.

We have the following loop: (stripped of the code that doesn't matter)

(while continue
  (forward-line -1)
  (back-to-indentation)
  (setq continue 
    (not (bobp))))

Your template has a leading space on the first line.

This means Emacs will back up to the first line, then:

1. Try to backup another line (no-op)
2. Go back-to-indentation (i.e. after the first space)
3. Check if it's at the beginning of the buffer. (it's not, point = 2)

There are other termination conditions in the loop, but they never apply. This is pretty tricky since it's tied to whitespace, which part of why it's so hard to track down. (How many files do you know that start with whitespace?)

It sounds like you already have a bug open, so I've not opened one.