replace-regex to remove first element from camel case function name - regex

Question

I have code like this:
<?= $this->Article->getShowComments(); ?>
and need to convert it to
{{ Article.showComments }}
everything is easy with simple regex: exception .getFooBar to .fooBar, how can I do this in Elisp, is there something like replace using a function like in javascript?

Answer 1

Set case-fold-search to nil:
M-x set-variable RET case-fold-search RET nil
Now, use the following command for the transformation:
M-x replace-regexp RET \_<\(?:[a-z0-9]\|\s_\)+\([A-Z]\) RET \,(downcase \1)
The first argument is the regexp to search for, the second is the replacement text.
The regexp is a little complicated, but essentially matches a symbol starting (\_< is symbol start) with either lowercase letters or digits ([a-z0-9]) or non-word symbol characters (\s_), followed by a single uppercase letter [A-Z]. The first non-grouping parenthesis \(?:…\) just groups the or-operator \|.
The second parenthesis around the uppercase letter is grouping, which creates the “reference” \1 for use in our replacement text.
We wrap the reference to the matched uppercase letter into the function downcase to convert it to lowercase. The \, in the replacement text just tells Emacs, that the following text is a proper sexp to be evaluated and not just a simple string.
Edit 1) The rx variant of this RE is probably easier to understand:
(and symbol-start
(one-or-more (or (any "a-z" "0-9") (syntax symbol)))
(group-n 1 (any "A-Z"))
Unfortunately you can't use RX expressions in replace-match.
Edit 2) replace-regexp is intended for interactive use only. It should not be used non-interactively, i.e. from Emacs Lisp. Notably, when used non-interactively, this function will not compile the replacement text, so the special \, escape will not work!
From Emacs Lisp, use re-search-forward and replace-match:
(let ((case-fold-search nil)
(regexp (rx symbol-start
(one-or-more (or (any "a-z" "0-9") (syntax symbol)))
(group-n 1 (any "A-Z")))))
(while (re-search-forward regexp nil 'no-error)
(replace-match (downcase (match-string 1)) 'fixed-case 'literal)))
Make sure to wrap this in with-current-buffer to make it operate on the right buffer.

Answer 2

Here's what I've got in my attic for this:
(defun CamelCase->underscore (str)
(mapconcat 'identity (CamelCase->list str) "_"))
(defun CamelCase->list (str)
(let ((case-fold-search nil)
(pos 0)
words)
(while (string-match ".[^A-Z]*" str pos)
(let ((word (downcase (match-string-no-properties 0 str))))
(if (> (length word) 1)
(push word words)
(setq words (cons (concat (car words) word)
(cdr words)))))
(setq pos (match-end 0)))
(reverse words)))
(CamelCase->underscore "getShowComments")
;; => "get_show_comments"
Just needs a bit of adapting for your case.
And here's the adaptation:
(defun CamelCase->something (str)
(let ((case-fold-search nil)
(pos 0)
words)
(while (string-match ".[^A-Z]*" str pos)
(let ((word (match-string-no-properties 0 str)))
(if (> (length word) 1)
(push word words)
(setq words (cons (concat (car words) word)
(cdr words)))))
(setq pos (match-end 0)))
(setq words (cdr (reverse words)))
(mapconcat 'identity
(cons (downcase (car words)) (cdr words))
"")))