=head1 NAME

mod_perl Coding Style Guide

=head1 Description

This document explains the coding style used in the core mod_perl
development and which should be followed by all core developers.

=head1 Coding Style Guide

We try hard to code mod_perl using an identical style. Because
everyone in the team should be able to read and understand the code as
quickly and easily as possible. Some will have to adjust their habits
for the benefit of all.

=over 4

=item * C code

mod_perl's C code follows the Apache style guide:
http://dev.apache.org/styleguide.html

=item * XS code

C code inside XS modules also follows the Apache style guide.

=item * Perl code

mod_perl's Perl code also follows the Apache style guide, in terms of
indentation, braces, etc. Style issues not covered by Apache style of
guide should be looked up in the I<perlstyle> manpage.

=back

Here are the rough guidelines with more stress on the Perl coding
style.

=over 4

=item Indentation and Tabs

Do use 4 characters indentation.

Do NOT use tabs.

Here is how to setup your editor to do the right thing:

=over

=item * x?emacs: cperl-mode

  .xemacs/custom.el:
  ------------------
  (custom-set-variables
     '(cperl-indent-level 4)
     '(cperl-continued-statement-offset 4)
     '(cperl-tab-always-indent t)
     '(indent-tabs-mode nil)
  )

=item * vim

  .vimrc:
  -------
  set expandtab " replaces any tab keypress with the appropriate number of spaces
  set tabstop=4 " sets tabs to 4 spaces

=back


=item Block Braces

Do use a style similar to K&R style, not the same. The following
example is the best guide:

Do:

   sub foo {
       my ($self, $cond, $baz, $taz) = @_;
  
       if ($cond) {
           bar();
       }
       else {
           $self->foo("one", 2, "...");
       }
  
       return $self;
   }

Don't:

   sub foo
   {
       my ($self,$bar,$baz,$taz)=@_;
       if( $cond )
       {
           &bar();
       } else { $self->foo ("one",2,"..."); }
       return $self;
   }

=item Lists and Arrays

Whenever you create a list or an array, always add a comma after the
last item. The reason for doing this is that it's highly probable that
new items will be appended to the end of the list in the future. If
the comma is missing and this isn't noticed, there will be an error.

Do:

  my @list = (
      "item1",
      "item2",
      "item3",
  );


Don't:

  my @list = (
      "item1",
      "item2",
      "item3"
  );

=item Last Statement in the Block

The same goes for C<;> in the last statement of the block. Almost
always add it even if it's not required, so when you add a new
statement you don't have to remember to add C<;> on a previous line.

Do:

  sub foo {
      statement1;
      statement2;
      statement3;
  }

Don't:

  sub foo {
      statement1;
      statement2;
      statement3
  }

=back



=head1 Function and Variable Prefixes Convention

=over 4

=item modperl_

The prefix for mod_perl C API functions.

=item MP_

The prefix for mod_perl C macros.

=item mpxs_

The prefix for mod_perl XS utility functions.

=item mp_xs_

The prefix for mod_perl I<generated> XS utility functions.

=item MPXS_

The prefix for mod_perl XSUBs with an XS() prototype.

=back







=head1 Coding Guidelines

The following are the Perl coding guidelines:


=head2 Global Variables

=over 4

=item avoid globals in general

=item avoid $&, $', $`

See C<Devel::SawAmpersand>'s I<README> that explains the evilness.
Under mod_perl everybody suffers when one is seen anywhere since the
interpreter is never shutdown.

=back


=head2 Modules

=over 4

=item Exporting/Importing

Avoid too much exporting/importing (glob aliases eat up memory)

When you do wish to import from a module try to use an explicit list or
tag whenever possible, e.g.:

  use POSIX qw(strftime);

When you do not wish to import from a module, always use an empty list
to avoid any import, e.g.:

  use IO::File ();

(explain how to use Apache2::Status to find imported/exported
functions)

=back


=head2 Methods

=over 4

=item indirect vs direct method calls

Avoid indirect method calls, e.g.

Do:

  CGI::Cookie->new

Don't:

  new CGI::Cookie

=back




=head2 Inheritance

=over 4

=item Avoid inheriting from certain modules

Exporter.
To avoid inheriting B<AutoLoader::AUTOLOAD>

Do:

  *import = \&Exporter::import;

Don't:

  @MyClass::ISA = qw(Exporter);

=back





=head2 Symbol tables

=over 4

=item %main::

stay away from C<main::> to avoid namespace clashes

=back

=head2 Use of $_ in loops

Avoid using C<$_> in loops unless it's a short loop and you don't call
any subs from within the loop. If the loop started as short and then
started to grow make sure to remove the use of C<$_>:

Do:

  for my $idx (1..100) {
      ....more than few lines...
      foo($idx);
      ....
  }

Don't:

   for (1..100) {
       ....more than a few statements...
       foo();
       ....
   }

Because foo() might change C<$_> if foo()'s author didn't localize C<$_>.

This is OK:

   for (1..100) {
       .... a few statements with no subs called
       # do something with $_
       ....
   }





=head1 Maintainers

Maintainer is the person(s) you should contact with updates,
corrections and patches.

Stas Bekman E<lt>stas *at* stason.orgE<gt>

=head1 Authors

=over

=item * 

Doug MacEachernE<lt>dougm (at) covalent.netE<gt>

=item *

Stas Bekman E<lt>stas (at) stason.orgE<gt>

=back

Only the major authors are listed above. For contributors see the
Changes file.

=cut

