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strictures(3)	      User Contributed Perl Documentation	 strictures(3)

NAME
       strictures - Turn on strict and make most warnings fatal

SYNOPSIS
	 use strictures	2;

       is equivalent to

	 use strict;
	 use warnings FATAL => 'all';
	 use warnings NONFATAL => qw(
	   exec
	   recursion
	   internal
	   malloc
	   newline
	   experimental
	   deprecated
	   portable
	 );
	 no warnings 'once';

       except when called from a file which matches:

	 (caller)[1] =~	/^(?:t|xt|lib|blib)[\\\/]/

       and when	either ".git", ".svn", ".hg", or ".bzr"	is present in the
       current directory (with the intention of	only forcing extra tests on
       the author side)	-- or when ".git", ".svn", ".hg", or ".bzr" is present
       two directories up along	with "dist.ini"	(which would indicate we are
       in a "dzil test"	operation, via Dist::Zilla) -- or when the
       "PERL_STRICTURES_EXTRA" environment variable is set, in which case it
       also does the equivalent	of

	 no indirect 'fatal';
	 no multidimensional;
	 no bareword::filehandles;

       Note that "PERL_STRICTURES_EXTRA" may at	some point add even more
       tests, with only	a minor	version	increase, but any changes to the
       effect of "use strictures" in normal mode will involve a	major version
       bump.

       If any of the extra testing modules are not present, strictures will
       complain	loudly,	once, via "warn()", and	then shut up. But you really
       should consider installing them,	they're	all great anti-footgun tools.

DESCRIPTION
       I've been writing the equivalent	of this	module at the top of my	code
       for about a year	now. I figured it was time to make it shorter.

       Things like the importer	in "use	Moose" don't help me because they turn
       warnings	on but don't make them fatal --	which from my point of view is
       useless because I want an exception to tell me my code isn't warnings-
       clean.

       Any time	I see a	warning	from my	code, that indicates a mistake.

       Any time	my code	encounters a mistake, I	want a crash --	not spew to
       STDERR and then unknown (and probably undesired)	subsequent behaviour.

       I also want to ensure that obvious coding mistakes, like	indirect
       object syntax (and not so obvious mistakes that cause things to
       accidentally compile as such) get caught, but not at the	cost of	an XS
       dependency and not at the cost of blowing things	up on another machine.

       Therefore, strictures turns on additional checking, but only when it
       thinks it's running in a	test file in a VCS checkout -- although	if
       this causes undesired behaviour this can	be overridden by setting the
       "PERL_STRICTURES_EXTRA" environment variable.

       If additional useful author side	checks come to mind, I'll add them to
       the "PERL_STRICTURES_EXTRA" code	path only -- this will result in a
       minor version increase (e.g. 1.000000 to	1.001000 (1.1.0) or similar).
       Any fixes only to the mechanism of this code will result	in a sub-
       version increase	(e.g. 1.000000 to 1.000001 (1.0.1)).

CATEGORY SELECTIONS
       strictures does not enable fatal	warnings for all categories.

       exec
	   Includes a warning that can cause your program to continue running
	   unintentionally after an internal fork.  Not	safe to	fatalize.

       recursion
	   Infinite recursion will end up overflowing the stack	eventually
	   anyway.

       internal
	   Triggers deep within	perl, in places	that are not safe to trap.

       malloc
	   Triggers deep within	perl, in places	that are not safe to trap.

       newline
	   Includes a warning for using	stat on	a valid	but suspect filename,
	   ending in a newline.

       experimental
	   Experimental	features are used intentionally.

       deprecated
	   Deprecations	will inherently	be added to in the future in
	   unexpected ways, so making them fatal won't be reliable.

       portable
	   Doesn't indicate an actual problem with the program,	only that it
	   may not behave properly if run on a different machine.

       once
	   Can't be fatalized.	Also triggers very inconsistently, so we just
	   disable it.

VERSIONS
       Depending on the	version	of strictures requested, different warnings
       will be enabled.	 If no specific	version	is requested, the current
       version's behavior will be used.	 Versions can be requested using
       perl's standard mechanism:

	 use strictures	2;

       Or, by passing in a "version" option:

	 use strictures	version	=> 2;

   VERSION 2
       Equivalent to:

	 use strict;
	 use warnings FATAL => 'all';
	 use warnings NONFATAL => qw(
	   exec
	   recursion
	   internal
	   malloc
	   newline
	   experimental
	   deprecated
	   portable
	 );
	 no warnings 'once';

	 # and if in dev mode:
	 no indirect 'fatal';
	 no multidimensional;
	 no bareword::filehandles;

       Additionally, any warnings created by modules using warnings::register
       or "warnings::register_categories()" will not be	fatalized.

   VERSION 1
       Equivalent to:

	 use strict;
	 use warnings FATAL => 'all';
	 # and if in dev mode:
	 no indirect 'fatal';
	 no multidimensional;
	 no bareword::filehandles;

METHODS
   import
       This method does	the setup work described above in "DESCRIPTION".
       Optionally accepts a "version" option to	request	a specific version's
       behavior.

   VERSION
       This method traps the "strictures->VERSION(1)" call produced by a use
       line with a version number on it	and does the version check.

EXTRA TESTING RATIONALE
       Every so	often, somebody	complains that they're deploying via "git
       pull" and that they don't want strictures to enable itself in this case
       -- and that setting "PERL_STRICTURES_EXTRA" to 0	isn't acceptable
       (additional ways	to disable extra testing would be welcome but the
       discussion never	seems to get that far).

       In order	to allow us to skip a couple of	stages and get straight	to a
       productive conversation,	here's my current rationale for	turning	the
       extra testing on	via a heuristic:

       The extra testing is all	stuff that only	ever blows up at compile time;
       this is intentional. So the oft-raised concern that it's	different code
       being tested is only sort of the	case --	none of	the modules involved
       affect the final	optree to my knowledge,	so the author gets some
       additional compile time crashes which he/she then fixes,	and the	rest
       of the testing is completely valid for all environments.

       The point of the	extra testing -- especially "no	indirect" -- is	to
       catch mistakes that newbie users	won't even realise are mistakes
       without help. For example,

	 foo { ... };

       where foo is an & prototyped sub	that you forgot	to import -- this is
       pernicious to track down	since all seems	fine until it gets called and
       you get a crash.	Worse still, you can fail to have imported it due to a
       circular	require, at which point	you have a load	order dependent	bug
       which I've seen before now only show up in production due to tiny
       differences between the production and the development environment. I
       wrote <http://shadow.cat/blog/matt-s-trout/indirect-but-still-fatal/>
       to explain this particular problem before strictures itself existed.

       As such,	in my experience so far	strictures' extra testing has avoided
       production versus development differences, not caused them.

       Additionally, strictures' policy	is very	much "try and provide as much
       protection as possible for newbies -- who won't think about whether
       there's an option to turn on or not" -- so having only the environment
       variable	is not sufficient to achieve that (I get to explain that you
       need to add "use	strict"	at least once a	week on	freenode #perl --
       newbies sometimes completely skip steps because they don't understand
       that that step is important).

       I make no claims	that the heuristic is perfect -- it's already been
       evolved significantly over time,	especially for 1.004 where we changed
       things to ensure	it only	fires on files in your checkout	(rather	than
       strictures-using	modules	you happened to	have installed,	which was just
       silly). However,	I hope the above clarifies why a heuristic approach is
       not only	necessary but desirable	from a point of	view of	providing new
       users with as much safety as possible, and will allow any future
       discussion on the subject to focus on "how do we	minimise annoyance to
       people deploying	from checkouts intentionally".

SEE ALSO
       o   indirect

       o   multidimensional

       o   bareword::filehandles

COMMUNITY AND SUPPORT
   IRC channel
       irc.perl.org #toolchain

       (or bug 'mst' in	query on there or freenode)

   Git repository
       Gitweb is on http://git.shadowcat.co.uk/	and the	clone URL is:

	 git clone git://git.shadowcat.co.uk/p5sagit/strictures.git

       The web interface to the	repository is at:

	 http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=p5sagit/strictures.git

AUTHOR
       mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>

CONTRIBUTORS
       Karen Etheridge (cpan:ETHER) <ether@cpan.org>

       Mithaldu	- Christian Walde (cpan:MITHALDU) <walde.christian@gmail.com>

       haarg - Graham Knop (cpan:HAARG)	<haarg@haarg.org>

COPYRIGHT
       Copyright (c) 2010 the strictures "AUTHOR" and "CONTRIBUTORS" as	listed
       above.

LICENSE
       This library is free software and may be	distributed under the same
       terms as	perl itself.

perl v5.32.1			  2019-03-10			 strictures(3)

NAME | SYNOPSIS | DESCRIPTION | CATEGORY SELECTIONS | VERSIONS | METHODS | EXTRA TESTING RATIONALE | SEE ALSO | COMMUNITY AND SUPPORT | AUTHOR | CONTRIBUTORS | COPYRIGHT | LICENSE

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