Add test for hargs:sexpression-p

[matsl]

What

Add test for hargs:sexpression-p.

Why

When reading through the doc string it struck me that it was not a perfect match for the functionality. So I decided to write some tests to verify the behavior. Here it is.

What looked wrong is that the doc string says the following:

If point follows an sexpression end character, the preceding sexpression is returned.  
If point precedes an sexpression start character, the following sexpression is returned.  
Otherwise, the innermost sexpression

As can be seen from the test the cases for point preceding the start character does not seems to work as expected.

Then I noticed that this function is only used in one place so maybe overkill to spent to much time on it but it felt like a generic function so might be worth fixing anyway!?

[rswgnu]

You are right, there was a bug in hargs:sexpression-p. To fix your PR here, you'll have to replace that function with the version below and then update your test function with the version below as well.

(defun hargs:sexpression-p (&optional no-recurse)
  "Return an sexpression at point as a string.
If point follows an sexpression end character, the preceding sexpression
is returned.  If point precedes an sexpression start character, the
following sexpression is returned.  Otherwise, the innermost sexpression
that point is within is returned or nil if none."
  (let ((not-quoted
	 '(condition-case ()
	      (not (and (eq (char-syntax (char-after (- (point) 2))) ?\\)
			(not (eq (char-syntax (char-after (- (point) 3))) ?\\))))
	    (error t))))
    (save-excursion
      (ignore-errors
	(cond ((and (eq (char-syntax (preceding-char)) ?\))
		    ;; Ignore quoted end chars.
		    (eval not-quoted))
	       (buffer-substring (point)
				 (progn (forward-sexp -1) (point))))
	      ((and (eq (char-syntax (following-char)) ?\()
		    ;; Ignore quoted begin chars.
		    (eval not-quoted))
	       (buffer-substring (point)
				 (progn (forward-sexp) (point))))
	      (no-recurse nil)
	      (t (save-excursion (up-list 1) (hargs:sexpression-p t))))))))


(ert-deftest hargs-tests--sexpression-p ()
  "Verify behavior of `hargs:sexpression-p'."
  (with-temp-buffer
    (insert " (setq var (+ 1 2))  ")
    ;; pos ->123456789012345678901
    (dolist (v '((1 nil nil)
                 (2 "(setq var (+ 1 2))" "(setq var (+ 1 2))")
                 (3 "(setq var (+ 1 2))" nil)
                 (4 "(setq var (+ 1 2))" nil)
                 (11 "(setq var (+ 1 2))" nil)
                 (12 "(+ 1 2)" "(+ 1 2)")
                 (13 "(+ 1 2)" nil)
                 (18 "(+ 1 2)" nil)
                 (19 "(+ 1 2)" "(+ 1 2)")
                 (20 "(setq var (+ 1 2))" "(setq var (+ 1 2))")
                 (21 nil nil)))
      (goto-char (car v))
      (should (string= (cadr v) (hargs:sexpression-p)))
      (should (string= (caddr v) (hargs:sexpression-p t))))))