Re: New ELPA package ada-lite

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I'd like to add a package ada-lite-mode to ELPA; code attached.  The
> intent is to be a mode for Ada files that's easier to install than the
> current ELPA ada-mode.

Sounds good, as long as the other ada-mode will be modified to (require
and) derive from (or extend) ada-lite.

Currently, if both ada-mode and ada-lite packages are installed and
activated, their autoloads will fight for the top spot of
`auto-mode-alist`.

A few more comments about the code:

> ;; To use ada-lite-mode for Ada files, put the following in your
> ;; emacs startup:
     ^^^^^
     Emacs


> ;; (require 'ada-lite-mode)

That shouldn't be necessary if the package is installed "the normal way".

> (defun ada-lite-font-lock-keywords ()
>   "Ada mode value for `font-lock-keywords'."
>   (list
>    (list (concat "\\_<" (regexp-opt ada-lite-keywords t) "\\_>") '(0 font-lock-keyword-face))
>    ))

I'd have split this into two to fit into the usual 80 columns.

> (defun ada-lite-syntax-propertize (start end)
>   "For `syntax-propertize-function'.
> Assign `syntax-table' properties in region START .. END.
> In particular, character constants are set to have string syntax."
>   ;; (info "(elisp)Syntax Properties")
>   ;;
>   ;; called from `syntax-propertize', inside save-excursion with-silent-modifications
>   (let ((inhibit-read-only t)
> 	(inhibit-point-motion-hooks t))

`inhibit-point-motion-hooks` is t (and obsolete) since Emacs-25.
And `inhibit-read-only` should already be t since we're within
`with-silent-modifications`.

>     (goto-char start)
>     (save-match-data

Why?

>       (while (re-search-forward
> 	      (concat
> 	       "[^[:alnum:])]\\('\\)[^'\n]\\('\\)"; 1, 2: character literal, not attribute
> 	       "\\|[^[:alnum:])]\\('''\\)"; 3: character literal '''
> 	       )
> 	      end t)
> 	;; syntax-propertize-extend-region-functions is set to
> 	;; syntax-propertize-wholelines by default. We assume no
> 	;; coding standard will permit a character literal at the
> 	;; start of a line (not preceded by whitespace).
> 	(cond
> 	 ((match-beginning 1)
> 	  (put-text-property
> 	   (match-beginning 1) (match-end 1) 'syntax-table '(7 . ?'))
> 	  (put-text-property
> 	   (match-beginning 2) (match-end 2) 'syntax-table '(7 . ?')))
> 	 ((match-beginning 3)
> 	  (put-text-property
> 	   (match-beginning 3) (1+ (match-beginning 3)) 'syntax-table '(7 . ?'))
> 	  (put-text-property
> 	   (1- (match-end 3)) (match-end 3) 'syntax-table '(7 . ?')))
> 	 )))))

I think

    (syntax-propertize-rules
     ("[^[:alnum:])]\\('\\)[^'\n]\\('\\)"
      (1 "\"'")
      (2 "\"'")
     ("[^[:alnum:])]\\('\\)'\\('\\)"
      (1 "\"'")
      (2 "\"'"))

would do basically the same, but:

- Is there a specific reason why you preferred to code it by hand
  (speed maybe?)
- The second char in "\"'" is unused (it's only used for open/close
  parentheses-like thingies).

You could merge the two into:

    (syntax-propertize-rules
     ("[^[:alnum:])]\\('\\)\\(?:'\\|[^'\n]\\)\\('\\)"
      (1 "\"")
      (2 "\""))


> (define-derived-mode ada-lite-mode prog-mode "ada-lite"

There's an autoload cookie missing here.

>   (set (make-local-variable 'syntax-propertize-function) #'ada-lite-syntax-propertize)
>   (syntax-ppss-flush-cache (point-min));; reparse with new function

Why/when have you found this explicit flush to be necessary?

>   (set (make-local-variable 'parse-sexp-ignore-comments) t)
>   (set (make-local-variable 'parse-sexp-lookup-properties) t)
>   (set 'case-fold-search t); Ada is case insensitive
>   (set 'completion-ignore-case t)
>   (set (make-local-variable 'comment-start) "--")
>   (set (make-local-variable 'comment-end) "")
>   (set (make-local-variable 'comment-start-skip) "---*[ \t]*")
>   (set (make-local-variable 'comment-multi-line) nil)

You can use `setq-local` on all of those.

> (defcustom ada-lite-server-exec nil
>   "Location of an Ada language server.
> If non-nil, should be an absolute path to an executable for the
> server; this allows specifying a development version. See
> `ada-lite-find-server' for default behaviour.")

A `defcustom` without :type is like a meringue without double cream,
(or like a churro without dulce de leche, depending on your religion).

> 		   (expand-file-name
> 		    (concat (file-name-directory gnat)
> 			    "../libexec/gnatstudio/als"))))))

Why not just

	   (expand-file-name "../libexec/gnatstudio/als"
	                     (file-name-directory gnat))))))

?

> (defun ada-lite-find-project (_dir)
>   "If ada-lite-mode, return ada-lite project.
> For `project-find-functions'"
>   (and (eq major-mode 'ada-lite-mode)

I recommend (derived-mode-p 'ada-lite-mode) instead?

> (if (featurep 'eglot)
>     (add-to-list 'eglot-server-programs (cons 'ada-lite-mode #'ada-lite-find-server))
>   (eval-after-load "eglot" '(add-to-list 'eglot-server-programs (cons 'ada-lite-mode #'ada-lite-find-server))))

AFAIK

   (with-eval-after-load 'eglot
     (add-to-list 'eglot-server-programs
                  (cons 'ada-lite-mode #'ada-lite-find-server)))

should do the same (including run the code right away if the feature
is already provided).


        Stefan