Re: Interpretation of a space in regexp isearch?

[Juri Linkov]

> 1. Info mode has its own variable `Info-search-whitespace-regexp'.
> Why is it necessary?  I guess there's a reason (which I don't know by
> now)

`Info-search-whitespace-regexp' is used in the regexp-based `Info-search'.
Its default value is the same as for `search-whitespace-regexp'
(actually it could inherit the default value directly from the value of
`search-whitespace-regexp').

> so it seems that your change should also affect to this variable.

Yes, these changes affect this variable.  The condition that checks for
`isearch-regexp' should be removed from `Info-search' like in the patch
below (could be installed after resolving other problems).

> 2. Why don't you include \n and \r by default in the regexp?  IMO
> that'd be TRT for most users.

The default value of `search-whitespace-regexp' is "\\s-+"
that means it matches whitespace including \n and \r by default.
However, some modes override this default whitespace syntax
where newlines are not whitespace.  For example, in Lisp
a newline ends a comment.  But currently you can't search
in comments without regard to line breaks anyway.
To implement this, `search-whitespace-regexp' should also
ignore the semicolon that starts a comment.

> 3.  Why should this feature be limited to _incremental_ searches?  I
> don't think it should.  The documentation states this limitation (see
> [1][2][3]) but according to the tests I've done, non-incremental
> searches also take `search-whitespace-regexp' into account.

By the term "non-incremental searches" do you mean
`M-x nonincremental-search-forward RET' or `C-s RET'?

PS: The patch for info.el:

=== modified file 'lisp/info.el'
--- lisp/info.el        2012-08-25 20:00:40 +0000
+++ lisp/info.el        2012-08-28 08:27:44 +0000
@@ -328,7 +328,7 @@ (defcustom Info-breadcrumbs-depth 4
   :type 'integer
   :group 'info)
 
-(defcustom Info-search-whitespace-regexp "\\s-+"
+(defcustom Info-search-whitespace-regexp search-whitespace-regexp
   "If non-nil, regular expression to match a sequence of whitespace chars.
 This applies to Info search for regular expressions.
 You might want to use something like \"[ \\t\\r\\n]+\" instead.
@@ -1892,9 +1892,7 @@ (defun Info-search (regexp &optional bou
                      (or (null found)
                          (not (run-hook-with-args-until-failure
                                'isearch-filter-predicates beg-found found))))
-           (let ((search-spaces-regexp
-                  (if (or (not isearch-mode) isearch-regexp)
-                      Info-search-whitespace-regexp)))
+           (let ((search-spaces-regexp Info-search-whitespace-regexp))
              (if (if backward
                      (re-search-backward regexp bound t)
                    (re-search-forward regexp bound t))
@@ -1914,9 +1912,7 @@ (defun Info-search (regexp &optional bou
          (if (null Info-current-subfile)
              (if isearch-mode
                  (signal 'search-failed (list regexp "at the end of manual"))
-               (let ((search-spaces-regexp
-                      (if (or (not isearch-mode) isearch-regexp)
-                          Info-search-whitespace-regexp)))
+               (let ((search-spaces-regexp Info-search-whitespace-regexp))
                  (if backward
                      (re-search-backward regexp)
                    (re-search-forward regexp))))
@@ -1975,9 +1971,7 @@ (defun Info-search (regexp &optional bou
                            (or (null found)
                                (not (run-hook-with-args-until-failure
                                      'isearch-filter-predicates beg-found 
found))))
-                 (let ((search-spaces-regexp
-                        (if (or (not isearch-mode) isearch-regexp)
-                            Info-search-whitespace-regexp)))
+                 (let ((search-spaces-regexp Info-search-whitespace-regexp))
                    (if (if backward
                            (re-search-backward regexp nil t)
                          (re-search-forward regexp nil t))