3 RT::StyleGuide - RT Style Guide
7 All code and documentation that is submitted to be included in the RT
8 distribution should follow the style in this document. This is not to
9 try to stifle your creativity, but to make life easier for everybody who
10 has to work with your code, and to aid those who are not quite sure how
13 These conventions below apply to perl modules, web programs, and
14 command-line programs, specifically, but also might apply to some
15 degree to any Perl code written for use in RT.
17 Note that these are all guidelines, not unbreakable rules. If you have
18 a really good need to break one of the rules herein, however, then it is
19 best to ask on the B<rt-devel> mailing list first.
21 Note that with much of this document, it is not so much the Right Way as
22 it is Our Way. We need to have conventions in order to make life easier
23 for everyone. So don't gripe, and just follow it, because you didn't
24 get a good grade in "Plays Well With Others" in kindergarten and you
25 want to make up for it now.
27 If you have any questions, please ask us on the B<rt-devel> mailing list:
29 http://www.bestpractical.com/rt/lists.html
31 We don't always follow this guide. We are making changes throughout
32 our code to be in line with it. But just because we didn't do
33 it yet, that is no excuse. Do it anyway. :-)
35 This document is subject to change at the whims of the core RT team.
36 We hope to add any significant changes at the bottom of the document.
39 =head1 CODING PRINCIPLES
43 We code everything to perl 5.6.1. Some features require advanced unicode
44 features in perl 5.8.0. It is acceptable that unicode features work only for
45 US-ASCII on perl 5.6.1.
50 All modules will be documented using the POD examples in the module
51 boilerplate. The function, purpose, use of the module will be
52 explained, and each public API will be documented with name,
53 description, inputs, outputs, side effects, etc.
55 If an array or hash reference is returned, document the size of the
56 array (including what each element is, as appropriate) and name each key
57 in the hash. For complex data structures, map out the structure as
58 appropriate (e.g., name each field returned for each column from a DB
59 call; yes, this means you shouldn't use "SELECT *", which you shouldn't
62 Also document what kind of data returned values are. Is it an integer,
63 a block of HTML, a boolean?
65 All command-line program options will be documented using the
66 boilerplate code for command-line programs, which doesn't yet exist.
67 Each available function, switch, etc. should be documented, along
68 with a statement of function, purpose, use of the program. Do not
69 use the same options as another program, for a different purpose.
71 All web templates should be documented with a statement of function,
72 purpose, and use in a mason comment block.
74 Any external documents, and documentation for command-line programs and
75 modules, should be written in POD, where appropriate. From there, they
76 can be translated to many formats with the various pod2* translators.
77 Read the perlpod manpage before writing any POD, because although POD is
78 not difficult, it is not what most people are used to. It is not a
79 regular markup language; it is just a way to make easy documentation
80 for translating to other formats. Read, and understand, the perlpod
81 manpage, and ask us or someone else who knows if you have any questions.
86 Our distribution versions use tuples, where the first number is the
87 major revision, the second number is the version, and third
88 number is the subversion. Odd-numbered versions are development
91 1.0.0 First release of RT 1
92 1.0.1 Second release of RT 1.0
94 1.1.0 First development release of RT 1.2 (or 2.0)
95 2.0.0 First release of RT 2
97 Versions can be modified with a hyphen followed by some text, for
98 special versions, or to give extra information. Examples:
100 2.0.0-pre1 Notes that this is not final, but preview
102 In perl 5.6.0, you can have versions like C<v2.0.0>, but this is not
103 allowed in previous versions of perl. So to convert a tuple version
104 string to a string to use with $VERSION, use a regular integer for
105 the revision, and three digits for version and subversion. Examples:
110 This way, perl can use the version strings in greater-than and
111 less-than comparisons.
116 All code should be self-documenting as much as possible. Only include
117 necessary comments. Use names like "$ticket_count", so you don't need to
123 Include any comments that are, or might be, necessary in order for
124 someone else to understand the code. Sometimes a simple one-line
125 comment is good to explain what the purpose of the following code is
126 for. Sometimes each line needs to be commented because of a complex
127 algorithm. Read Kernighan & Pike's I<Practice of Programming> about
128 commenting. Good stuff, Maynard.
131 =head2 Warnings and Strict
133 All code must compile and run cleanly with "use strict" enabled and the
134 perl "-w" (warnings) option on. If you must do something that -w or
135 strict complains about, there are workarounds, but the chances that you
136 really need to do it that way are remote.
138 =head2 Lexical Variables
140 Use only lexical variables, except for special global variables
141 ($VERSION, %ENV, @ISA, $!, etc.) or very special circumstances (see
142 %HTML::Mason::Commands::session ). Global variables
143 for regular use are never appropriate. When necessary, "declare"
144 globals with "use vars" or "our()".
146 A lexical variable is created with my(). A global variable is
147 pre-existing (if it is a special variable), or it pops into existence
148 when it is used. local() is used to tell perl to assign a temporary
149 value to a variable. This should only be used with special variables,
150 like $/, or in special circumstances. If you must assign to any global
151 variable, consider whether or not you should use local().
153 local() may also be used on elements of arrays and hashes, though there
154 is seldom a need to do it, and you shouldn't.
159 Do not export anything from a module by default. Feel free to put
160 anything you want to in @EXPORT_OK, so users of your modules can
161 explicitly ask for symbols (e.g., "use Something::Something qw(getFoo
162 setFoo)"), but do not export them by default.
165 =head2 Pass by Reference
167 Arrays and hashes should be passed to and from functions by reference
168 only. Note that a list and an array are NOT the same thing. This
171 return($user, $form, $constants);
173 An exception might be a temporary array of discrete arguments:
175 my @return = ($user, $form);
176 push @return, $constants if $flag;
179 Although, usually, this is better (faster, easier to read, etc.):
182 return($user, $form, $constants);
184 return($user, $form);
187 We need to talk about Class::ReturnValue here.
190 =head2 Garbage Collection
192 Perl does pretty good garbage collection for you. It will automatically
193 clean up lexical variables that have gone out of scope and objects whose
194 references have gone away. Normally you don't need to worry about
195 cleaning up after yourself, if using lexicals.
197 However, some glue code, code compiled in C and linked to Perl, might
198 not automatically clean up for you. In such cases, clean up for
199 yourself. If there is a method in that glue to dispose or destruct,
200 then use it as appropriate.
202 Also, if you have a long-running function that has a large data
203 structure in it, it is polite to free up the memory as soon as you are
204 done with it, if possible.
206 my $huge_data_structure = get_huge_data_structure();
207 do_something_with($huge_data_structure);
208 undef $huge_data_structure;
212 All object classes must provide a DESTROY method. If it won't do
213 anything, provide it anyway:
219 =head2 die() and exit()
221 Don't do it. Do not die() or exit() from a web template or module. Do
222 not call C<kill 9, $$>. Don't do it.
224 In command-line programs, do as you please.
229 Do not use @_. Use shift. shift may take more lines, but Jesse thinks it
230 leads to cleaner code.
232 my $var = shift; # right
233 my($var) = @_; # ick. no
234 sub foo { uc $_[0] } # icky. sometimes ok.
237 my($var1, $var2) = (shift, shift); # Um, no.
239 my $var1 = shift; # right
246 Modules should provide test code, with documentation on how to use
247 it. Test::Inline allows tests to be embedded in code. Test::More makes it
248 easy to create tests. Any code you write should have a testsuite.
249 Any code you alter should have a test suite. If a patch comes in without
250 tests, there is something wrong.
252 When altering code, you must run the test harness before submitting a patch
253 or committing code to the repository.
255 "make regression" will extract inline tests, blow away the system database
256 and run the test suite.
258 "make regression-quiet" will do all that and not print the "ok" lines.
264 Always report errors using $RT::Logger. It's a Log::Dispatch object.
265 Unlike message meant for the user, log messages are not to be
268 There are several different levels ($RT::Logger methods) of logging:
274 Used for messages only needed during system debugging.
278 Should be used to describe "system-critical" events which aren't errors.
279 Examples: creating users, deleting users, creating tickets, creating queues,
280 sending email (message id, time, recipients), recieving mail, changing
281 passwords, changing access control, superuser logins)
285 Used for RT-generated failures during execution.
289 Should be used for messages when an action can not be completed due to some
290 error condition beyond our control.
294 In the web UI and modules, never print directly to STDERR. Do not print
295 directly to STDOUT, unless you need to print directly to the user's console.
297 In command-line programs, feel free to print to STDERR and STDOUT as
298 needed for direct console communication. But for actual error reporting,
304 Always check return values from system calls, including open(),
305 close(), mkdir(), or anything else that talks directly to the system.
306 Perl built-in system calls return the error in $!; some functions in
307 modules might return an error in $@ or some other way, so read the module's
308 documentation if you don't know. Always do something, even if it is
309 just calling $RT::Logger->warning(), when the return value is not what you'd expect.
315 Much of the style section is taken from the perlsyle manpage. We make
316 some changes to it here, but it wouldn't be a bad idea to read that
325 "RT" is the name of the project. "RT" is, optionally, the
326 specific name for the actual file distribution. That's it.
328 While we sometimes use "RT2" or "RT3", that's shortand that's really
329 not recommended. The name of the project is "RT".
331 To specify a major version, use "RT 3.0".
332 To specify a specific release, use "RT 3.0.12"
334 =item function vs. sub(routine) vs. method
336 Just because it is the Perl Way (not necessarily right for all
337 languages, but the documented terminology in the perl documentation),
338 "method" should be used only to refer to a subroutine that are object
339 methods or class methods; that is, these are functions that are used
340 with OOP that always take either an object or a class as the first
341 argument. Regular subroutines, ones that are not object or class
342 methods, are functions. Class methods that create and return an object
343 are optionally called constructors.
347 "users" are normally users of RT, the ones hitting the site; if using
348 it in any other context, specify.
349 "system users" are user
350 names on the operating system. "database users" are the user names in
351 the database server. None of these needs to be capitalized.
358 Don't use single-character variables, except as iterator variables.
360 Don't use two-character variables just to spite us over the above rule.
362 Constants are in all caps; these are variables whose value will I<never>
363 change during the course of the program.
365 $Minimum = 10; # wrong
366 $MAXIMUM = 50; # right
368 Other variables are lowercase, with underscores separating the words.
369 They words used should, in general, form a noun (usually singular),
370 unless the variable is a flag used to denote some action that should be
371 taken, in which case they should be verbs (or gerunds, as appropriate)
372 describing that action.
374 $thisVar = 'foo'; # wrong
375 $this_var = 'foo'; # right
376 $work_hard = 1; # right, verb, boolean flag
377 $running_fast = 0; # right, gerund, boolean flag
379 Arrays and hashes should be plural nouns, whether as regular arrays and
380 hashes or array and hash references. Do not name references with "ref"
381 or the data type in the name.
383 @stories = (1, 2, 3); # right
384 $comment_ref = [4, 5, 6]; # wrong
385 $comments = [4, 5, 6]; # right
386 $comment = $comments->[0]; # right
388 Make the name descriptive. Don't use variables like "$sc" when you
389 could call it "$story_count". See L<"Comments">.
391 There are several variables in RT that are used throughout the code,
392 that you should use in your code. Do not use these variable names for
393 anything other than how they are normally used, and do not use any
394 other variable names in their place. Some of these are:
396 $self # first named argument in object method
398 Subroutines (except for special cases, like AUTOLOAD and simple accessors)
399 begin with a verb, with words following to complete the action. Accessors
400 don't start with "Get" if they're just the name of the attribute.
402 Accessors which return an object should end with the suffix Obj.
404 This section needs clarification for RT.
406 Words begin with a capital letter. They
407 should as clearly as possible describe the activity to be peformed, and
408 the data to be returned.
416 Subroutines beginning with C<_> are special: they are not to be used
417 outside the current object. There is not to be enforced by the code
418 itself, but by someone very big and very scary.
420 For large for() loops, do not use $_, but name the variable.
421 Do not use $_ (or assume it) except for when it is absolutely
422 clear what is going on, or when it is required (such as with
426 print; # OK; everyone knows this one
427 print uc; # wrong; few people know this
428 print uc $_; # better
431 Note that the special variable C<_> I<should> be used when possible.
432 It is a placeholder that can be passed to stat() and the file test
433 operators, that saves perl a trip to re-stat the file. In the
434 example below, using C<$file> over for each file test, instead of
435 C<_> for subsequent uses, is a performance hit. You should be
436 careful that the last-tested file is what you think it is, though.
438 if (-d $file) { # $file is a directory
440 } elsif (-l _) { # $file is a symlink
444 Package names begin with a capital letter in each word, followed by
445 lower case letters (for the most part). Multiple words should be StudlyCapped.
448 RT::Database::MySQL # proper name
449 RT::Display::Provider # good
450 RT::CustomField # not so good, but OK
452 Plugin modules should begin with "RTx::", followed by the name
455 =head1 Code formatting
457 Use perltidy. Anything we say here is wrong if it conflicts with what
458 perltidy does. Your perltidyrc should read:
460 -lp -vt=2 -vtc=2 -nsfs -bar
462 =head2 Indents and Blank Space
464 All indents should be tabs. Set your tab stops whatever you want them
465 to be; I use 8 spaces per tabs.
467 No space before a semicolon that closes a statement.
472 Line up corresponding items vertically.
478 open(FILE, $fh) or die $!;
479 open(FILE2, $fh2) or die $!;
481 $rot13 =~ tr[abcedfghijklmnopqrstuvwxyz]
482 [nopqrstuvwxyzabcdefghijklm];
484 # note we use a-mn-z instead of a-z,
489 Put blank lines between groups of code that do different things. Put
490 blank lines after your variable declarations. Put a blank line before a
491 final return() statement. Put a blank line following a block (and
492 before, with the exception of comment lines).
496 # this is my function!
499 my $obj = new Constructor;
514 For control structures, there is a space between the keyword and opening
515 parenthesis. For functions, there is not.
523 Be careful about list vs. scalar context with parentheses!
525 my @array = ('a', 'b', 'c');
526 my($first_element) = @array; # a
527 my($first_element) = ('a', 'b', 'c'); # a
528 my $element_count = @array; # 3
529 my $last_element = ('a', 'b', 'c'); # c
531 Always include parentheses after functions, even if there are no arguments.
532 There are some exceptions, such as list operators (like print) and unary
533 operators (like undef, delete, uc).
535 There is no space inside the parentheses, unless it is needed for
538 for ( map { [ $_, 1 ] } @list ) # OK
539 for ( @list ) # not really OK, not horrible
541 On multi-line expressions, match up the closing parenthesis with either
542 the opening statement, or the opening parenthesis, whichever works best.
550 if ($foo && $bar && $baz
556 Whether or not there is space following a closing parenthesis is
557 dependent on what it is that follows.
559 print foo(@bar), baz(@buz) if $xyzzy;
561 Note also that parentheses around single-statement control expressions,
562 as in C<if $xyzzy>, are optional (and discouraged) C<if> it is I<absolutely>
563 clear -- to a programmer -- what is going on. There is absolutely no
564 need for parentheses around C<$xyzzy> above, so leaving them out enhances
565 readability. Use your best discretion. Better to include them, if
566 there is any question.
568 The same essentially goes for perl's built-in functions, when there is
569 nothing confusing about what is going on (for example, there is only one
570 function call in the statement, or the function call is separated by a
571 flow control operator). User-supplied functions must always include
574 print 1, 2, 3; # good
575 delete $hash{key} if isAnon($uid); # good
578 However, if there is any possible confusion at all, then include the
579 parentheses. Remember the words of Larry Wall in the perlstyle manpage:
581 When in doubt, parenthesize. At the very least it will
582 let some poor schmuck bounce on the % key in vi.
584 Even if you aren't in doubt, consider the mental welfare
585 of the person who has to maintain the code after you, and
586 who will probably put parens in the wrong place.
588 So leave them out when it is absoutely clear to a programmer, but if
589 there is any question, leave them in.
594 (This is about control braces, not hash/data structure braces.)
596 There is always a space befor the opening brace.
598 while (<$fh>){ # wrong
599 while (<$fh>) { # right
601 A one-line block may be put on one line, and the semicolon may be
604 for (@list) { print }
606 Otherwise, finish each statement with a semicolon, put the keyword and
607 opening curly on the first line, and the ending curly lined up with the
615 Generally, we prefer "uncuddled elses":
624 _If_ the if statement is very brief, sometimes "cuddling" the else makes code more readable. Feel free to cuddle them in that case:
635 Put space around most operators. The primary exception is the for
636 aesthetics; e.g., sometimes the space around "**" is ommitted,
637 and there is never a space before a ",", but always after.
639 print $x , $y; # wrong
640 print $x, $y; # right
645 Note that "&&" and "||" have a higher precedence than "and" and "or".
646 Other than that, they are exactly the same. It is best to use the lower
647 precedence version for control, and the higher for testing/returning
650 $bool = $flag1 or $flag2; # WRONG (doesn't work)
651 $value = $foo || $bar; # right
652 open(FILE, $file) or die $!;
654 $true = foo($bar) && baz($buz);
655 foo($bar) and baz($buz);
657 Note that "and" is seldom ever used, because the statement above is
658 better written using "if":
660 baz($buz) if foo($bar);
662 Most of the time, the confusion between and/&&, or/|| can be alleviated
663 by using parentheses. If you want to leave off the parentheses then you
664 I<must> use the proper operator. But if you use parentheses -- and
665 normally, you should, if there is any question at all -- then it doesn't
666 matter which you use. Use whichever is most readable and aesthetically
667 pleasing to you at the time, and be consistent within your block of code.
669 Break long lines AFTER operators, except for "and", "or", "&&", "||".
670 Try to keep the two parts to a binary operator (an operator that
671 has two operands) together when possible.
673 print "foo" . "bar" . "baz"
676 print "foo" . "bar" . "baz" .
679 print $foo unless $x == 3 && $y ==
680 4 && $z == 5; # wrong
682 print $foo unless $x == 3 && $y == 4
688 Put space around a complex subscript inside the brackets or braces.
690 $foo{$bar{baz}{buz}}; # OK
691 $foo{ $bar{baz}{buz} }; # better
693 In general, use single-quotes around literals, and double-quotes
694 when the text needs to be interpolated.
696 It is OK to omit quotes around names in braces and when using
697 the => operator, but be careful not to use a name that doubles as
698 a function; in that case, quote.
700 $what{'time'}{it}{is} = time();
702 When making compound statements, put the primary action first.
704 open(FILE, $fh) or die $!; # right
705 die $! unless open(FILE, $fh); # wrong
707 print "Starting\n" if $verbose; # right
708 $verbose && print "Starting\n"; # wrong
711 Use here-docs instead of repeated print statements.
714 This is a whole bunch of text.
715 I like it. I don't need to worry about messing
716 with lots of print statements and lining them up.
719 Just remember that unless you put single quotes around your here-doc
720 token (<<'EOT'), the text will be interpolated, so escape any "$" or "@"
723 =head1 INTERNATIONALIZATION
726 =head2 String extraction styleguide
732 Templates should use the /l filtering component to call the localisation
737 Should become <&|/l&>Foo!</&>
739 All newlines should be removed from localized strings, to make it easy to
740 grep the codebase for strings to be localized
746 Should become <&|/l&>Foo Bar Baz</&>
749 Variable subsititutions should be moved to Locale::MakeText format
751 The string Hello, <%$name %>
753 should become <&|/l, $name &>Hello, [_1]</&>
756 Multiple variables work just like single variables
758 The string You found <%$num%> tickets in queue <%$queue%>
760 should become <&|/l, $num, $queue &>You found [_1] tickets in queue [_2]</&>
762 When subcomponents are called in the middle of a phrase, they need to be escaped
765 The string <input type="submit" value="New ticket in"> <& /Elements/SelectNewTicketQueue&>
767 should become <&|/l, $m->scomp('/Elements/SelectNewTicketQueue')&><input type="submit" value="New ticket in"> [_1]</&>
772 The string <& /Elements/TitleBoxStart, width=> "40%", titleright => "RT $RT::VERSION for $RT::rtname", title => 'Login' &>
774 should become <& /Elements/TitleBoxStart,
776 titleright => loc("RT [_1] for [_2]",$RT::VERSION, $RT::rtname),
777 title => loc('Login'),
785 Within RT's core code, every module has a localization handle available through the 'loc' method:
787 The code return ( $id, "Queue created" );
789 should become return ( $id, $self->loc("Queue created") );
791 When returning or localizing a single string, the "extra" set of parenthesis () should be omitted.
793 The code return ("Subject changed to ". $self->Data );
795 should become return $self->loc( "Subject changed to [_1]", $self->Data );
798 It is important not to localize the names of rights or statuses within RT's core, as there is logic that depends on them as string identifiers. The proper place to localize these values is when they're presented for display in the web or commandline interfaces.
803 =head1 CODING PRCEDURE
805 This is for new programs, modules, specific APIs, or anything else.
809 =item Present idea to rt-devel
811 We may know of a better way to approach the problem, or know of an
812 existing way to deal with it, or know someone else is working on it.
813 This is mostly informal, but a fairly complete explanation for the need
814 and use of the code should be provided.
817 =item Present complete specs to rt-devel
819 The complete proposed API should be submitted for
820 approval and discussion. For web and command-line programs, present the
821 functionality and interface (op codes, command-lin switches, etc.).
823 The best way to do this is to take the documentation portion of the
824 boilerplate and fill it in. You can make changes later if necessary,
825 but fill it in as much as you can.
829 =item Prepare for code review
831 When you are done, the code will undergo a code review by a member of
832 the core team, or someone picked by the core team. This is not to
833 belittle you (that's just a nice side effect), it is to make sure that
834 you understand your code, that we understand your code, that it won't
835 break other code, that it follows the documentation and existing
836 proposal. It is to check for possible optimizations or better ways of
839 Note that all code is expected to follow the coding principles and style
840 guide contained in this document.
845 After the code is done (possibly going through multiple code reviews),
846 if you do not have repository access, submit it to rt-<major-version>-bugs@fsck.com as a unified diff. From that point on, it'll be handled by someone with repository access.
851 =head1 BUG REPORTS, PATCHES
853 Use rt-<major-version>-bugs@fsck.com for I<any> bug that is not
854 being fixed immediately. If it is not in RT, there
855 is a good chance it will not be dealt with.
857 Send patches to rt-<major-version>-bugs@fsck.com, too. Use C<diff
864 Talk about DBIx::SearchBuilder
868 cascading style sheets
870 Talk about adding a new translation
872 Talk more about logging
876 Adapted from Slash Styleguide by jesse - 20 Dec, 2002