How can I make emacs' cperl-mode indent all statement continuations by only one level?

Question

In emacs' cperl-mode, lines that continute a statement from a previous line are indented by one level:

my $var
  = (1+1)
  * (2+2)
  / (3+3);

However, if the statement does not begin at zero indentation because it is inside a block, then if you break your statement onto a third line, you get another level of indentation, and so on:

sub break_my_indentation {
  my $var
    = (1+1)
      * (2+2)
        / (3+3);
  return "Indentation is broken.";
}

Is there any way to fix this so that statements are indented the same way inside blocks as they are outside? I would like the second example to look like this:

sub fix_my_indentation {
  my $var
    = (1+1)
    * (2+2)
    / (3+3);
  return "Indentation is fixed.";
}

Answer 1

I confirm that the behavior you describe is present, but, from reading the sources and running under the debugger, it is not obvious that there is a customization which gets you the behavior you (and I) want.

Therefore I think this is a bug in cperl-mode.

The fix is:

=== modified file 'lisp/progmodes/cperl-mode.el'
--- lisp/progmodes/cperl-mode.el    2012-12-01 05:09:12 +0000
+++ lisp/progmodes/cperl-mode.el    2012-12-26 16:29:19 +0000
@@ -3120,7 +3121,9 @@ and closing parentheses and brackets."
     ((eq 'continuation (elt i 0))
      ;; [continuation statement-start char-after is-block is-brace]
      (goto-char (elt i 1))     ; statement-start
-     (+ (if (memq (elt i 2) (append "}])" nil)) ; char-after
+     (+ (if (or (memq (elt i 2) (append "}])" nil)) ; char-after
+                     (eq 'continuation ; do not repeat cperl-close-paren-offset
+                         (elt (cperl-sniff-for-indent parse-data) 0)))
         0          ; Closing parenth
           cperl-continued-statement-offset)
         (if (or (elt i 3)      ; is-block

Please test this patch; if you are happy with it, I will add a customization to enable it.

Answer 2

cperl-mode don't have this problem by default. By default, it indents like this :

my $var
  = (1+1)
  * (2+2)
  / (3+3);

You have a customization that prevents cperl-mode to indent correctly. See cperl-indent-rules-alist variable for configuration of the indent.

Answer 3

As @jerome-radix suggests, the problem you're experiencing doesn't happen with cperl-mode by default. The problem could certainly by in cperl-indent-rules-alist, but there are a number of other places to look.

What version of the mode are you using? C-h v cperl-version RET

When debugging this kind of question you need to start with a couple of basic things to see if you can reproduce the error. First let everyone know what M-x emacs-version you are running. Then eliminate your own customizations from the equation by running emacs -q to avoid loading your init file at startup:

--no-init-file, -q          load neither ~/.emacs nor default.el

If you can still reproduce the problem with your own init file turned off, then go a step further and turn it off at the system level with emacs -Q:

--quick, -Q                 equivalent to:
                              -q --no-site-file --no-site-lisp --no-splash