[emacs-w3m:13082] Re: always text/plain on ASCII text

In [emacs-w3m:13081]
On Thu, 24 Jan 2019 06:08:05 -0500, Boruch Baum wrote:
> Katsumi-san,

> I made an attempt to create a defcustom for the variable. The following
> seemed good but fails to match. Any ideas?

> (defcustom my-test nil

First of all, please don't use defcutom for w3m-content-type-alist
because its default value inherits the value of mailcap-mime-data
that inherits the contents of user's ~/.mailcap file.  So, the
default value will vary and the use of defcustom is unsuitable with
it (I've made mailcap-mime-data defcustom'd in Emacs mistakenly
 once before but withdrawn).

Anyway, there are three reasons your custom type mismatching.

1. emacs-w3m bug

(defvar w3m-content-type-alist
[...]
	   ("application/x-bzip2" "\\.bz2\\'" nil nil nil)
	   ("application/x-gzip" "\\.gz\\'" nil nil nil)))

  Maybe those `nil' nil nil' should be fixed to `nil nil'.

2. Too much parens

  (group    :tag "External command and parameters\n"  :indent 16
    (string :format "Command: %v")
    (repeat :tag "Command parameters"
      (string :format "Command parameter: %v\n")))

  This matches ("command" ("param"..)), not ("command" "param"..).

3. No `nil' choice in the 2nd, 3rd, and 4th items

Here is a version that works.  Try:

(setq my-test
      (assoc-delete-all "\\`application/x-[bg]zip2?\\'"
			(copy-sequence w3m-content-type-alist)
			(lambda (a b) (string-match b a))))

and M-x customize-option RET my-test RET.

(defcustom my-test nil
  "doc string"
  :group 'w3m
  :type
  '(repeat
    (group
     :indent 12
     (string :tag "Mimetype")
     (radio (const nil) (string :tag "Regexp of suffix"))
     (choice :tag "Method" :indent 16
	     (const nil)
	     (function :tag "Lisp function")
	     (cons :tag "External command and parameters\n" :indent 16
		   (string :format "Command: %v")
		   (repeat :tag "Command parameters"
			   (radio :format "\n%v"
				  (const file) (const url) string))))
     (choice :tag "Override"
	     (const nil)
	     (function :tag "Lisp function" :format "Lisp function: %v\n")
	     (string   :tag "Content type" :format "Content type: %v\n\n")))))