From feadec307da148af70cf87013c99771ca4db91e4 Mon Sep 17 00:00:00 2001 From: Phillip Lord Date: Fri, 7 Aug 2015 22:12:59 +0100 Subject: [PATCH] Improve error signalling for seq-subseq. The existing behaviour for seq-subseq is to error when indexes are too large, but to silently ignore numbers which are too negative for lists. String and vector handling errors in both cases. This has been regularlised. Error signalling behaviour has been explicitly added to the docstring of seq-subseq, and also to cl-subseq which largely defers to seq-subseq (and is therefore also impacted by this change). Tests have been added for these exceptional cases, as well as one non exceptional base case. --- lisp/emacs-lisp/cl-extra.el | 4 +++- lisp/emacs-lisp/seq.el | 7 ++++++- test/automated/seq-tests.el | 7 ++++++- 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/lisp/emacs-lisp/cl-extra.el b/lisp/emacs-lisp/cl-extra.el index 101864d3721..9742014db0c 100644 --- a/lisp/emacs-lisp/cl-extra.el +++ b/lisp/emacs-lisp/cl-extra.el @@ -518,7 +518,9 @@ This sets the values of: `cl-most-positive-float', `cl-most-negative-float', (defun cl-subseq (seq start &optional end) "Return the subsequence of SEQ from START to END. If END is omitted, it defaults to the length of the sequence. -If START or END is negative, it counts from the end." +If START or END is negative, it counts from the end. +Signal an error if START or END are outside of the sequence (i.e +too large if positive or too small if negative)" (declare (gv-setter (lambda (new) (macroexp-let2 nil new new diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el index 9eed36eb68c..038b20e3b5e 100644 --- a/lisp/emacs-lisp/seq.el +++ b/lisp/emacs-lisp/seq.el @@ -221,12 +221,17 @@ TESTFN is used to compare elements, or `equal' if TESTFN is nil." (defun seq-subseq (seq start &optional end) "Return the subsequence of SEQ from START to END. If END is omitted, it defaults to the length of the sequence. -If START or END is negative, it counts from the end." +If START or END is negative, it counts from the end. + +Signal an error if START or END are outside of the sequence (i.e +too large if positive or too small if negative)" (cond ((or (stringp seq) (vectorp seq)) (substring seq start end)) ((listp seq) (let (len (errtext (format "Bad bounding indices: %s, %s" start end))) (and end (< end 0) (setq end (+ end (setq len (seq-length seq))))) (if (< start 0) (setq start (+ start (or len (setq len (seq-length seq)))))) + (unless (>= start 0) + (error "%s" errtext)) (when (> start 0) (setq seq (nthcdr (1- start) seq)) (or seq (error "%s" errtext)) diff --git a/test/automated/seq-tests.el b/test/automated/seq-tests.el index 3643ce53cb0..74c0700759e 100644 --- a/test/automated/seq-tests.el +++ b/test/automated/seq-tests.el @@ -187,7 +187,12 @@ Evaluate BODY for each created sequence. (should-not (seq-subseq '(1 2 3) 3)) (should (seq-subseq '(1 2 3) -3)) (should-error (seq-subseq '(1 2 3) 1 4)) - (should (seq-subseq '(1 2 3) 1 3))) + (should (seq-subseq '(1 2 3) 1 3)) + (should-error (seq-subseq '() -1)) + (should-error (seq-subseq [] -1)) + (should-error (seq-subseq "" -1)) + (should-not (seq-subseq '() 0)) + (should-error(seq-subseq '() 0 -1))) (ert-deftest test-seq-concatenate () (with-test-sequences (seq '(2 4 6)) -- 2.39.5