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1 | =head1 NAME |
2 | ||
3 | perlmodstyle - Perl module style guide | |
4 | ||
5 | =head1 INTRODUCTION | |
6 | ||
7 | This document attempts to describe the Perl Community's "best practice" | |
8 | for writing Perl modules. It extends the recommendations found in | |
9 | L<perlstyle> , which should be considered required reading | |
10 | before reading this document. | |
11 | ||
12 | While this document is intended to be useful to all module authors, it is | |
13 | particularly aimed at authors who wish to publish their modules on CPAN. | |
14 | ||
15 | The focus is on elements of style which are visible to the users of a | |
16 | module, rather than those parts which are only seen by the module's | |
17 | developers. However, many of the guidelines presented in this document | |
18 | can be extrapolated and applied successfully to a module's internals. | |
19 | ||
20 | This document differs from L<perlnewmod> in that it is a style guide | |
21 | rather than a tutorial on creating CPAN modules. It provides a | |
22 | checklist against which modules can be compared to determine whether | |
23 | they conform to best practice, without necessarily describing in detail | |
24 | how to achieve this. | |
25 | ||
26 | All the advice contained in this document has been gleaned from | |
27 | extensive conversations with experienced CPAN authors and users. Every | |
28 | piece of advice given here is the result of previous mistakes. This | |
29 | information is here to help you avoid the same mistakes and the extra | |
30 | work that would inevitably be required to fix them. | |
31 | ||
32 | The first section of this document provides an itemized checklist; | |
33 | subsequent sections provide a more detailed discussion of the items on | |
34 | the list. The final section, "Common Pitfalls", describes some of the | |
35 | most popular mistakes made by CPAN authors. | |
36 | ||
37 | =head1 QUICK CHECKLIST | |
38 | ||
39 | For more detail on each item in this checklist, see below. | |
40 | ||
41 | =head2 Before you start | |
42 | ||
43 | =over 4 | |
44 | ||
45 | =item * | |
46 | ||
47 | Don't re-invent the wheel | |
48 | ||
49 | =item * | |
50 | ||
51 | Patch, extend or subclass an existing module where possible | |
52 | ||
53 | =item * | |
54 | ||
55 | Do one thing and do it well | |
56 | ||
57 | =item * | |
58 | ||
59 | Choose an appropriate name | |
60 | ||
61 | =back | |
62 | ||
63 | =head2 The API | |
64 | ||
65 | =over 4 | |
66 | ||
67 | =item * | |
68 | ||
69 | API should be understandable by the average programmer | |
70 | ||
71 | =item * | |
72 | ||
73 | Simple methods for simple tasks | |
74 | ||
75 | =item * | |
76 | ||
77 | Separate functionality from output | |
78 | ||
79 | =item * | |
80 | ||
81 | Consistent naming of subroutines or methods | |
82 | ||
83 | =item * | |
84 | ||
85 | Use named parameters (a hash or hashref) when there are more than two | |
86 | parameters | |
87 | ||
88 | =back | |
89 | ||
90 | =head2 Stability | |
91 | ||
92 | =over 4 | |
93 | ||
94 | =item * | |
95 | ||
96 | Ensure your module works under C<use strict> and C<-w> | |
97 | ||
98 | =item * | |
99 | ||
100 | Stable modules should maintain backwards compatibility | |
101 | ||
102 | =back | |
103 | ||
104 | =head2 Documentation | |
105 | ||
106 | =over 4 | |
107 | ||
108 | =item * | |
109 | ||
110 | Write documentation in POD | |
111 | ||
112 | =item * | |
113 | ||
114 | Document purpose, scope and target applications | |
115 | ||
116 | =item * | |
117 | ||
118 | Document each publically accessible method or subroutine, including params and return values | |
119 | ||
120 | =item * | |
121 | ||
122 | Give examples of use in your documentation | |
123 | ||
124 | =item * | |
125 | ||
126 | Provide a README file and perhaps also release notes, changelog, etc | |
127 | ||
128 | =item * | |
129 | ||
130 | Provide links to further information (URL, email) | |
131 | ||
132 | =back | |
133 | ||
134 | =head2 Release considerations | |
135 | ||
136 | =over 4 | |
137 | ||
138 | =item * | |
139 | ||
ff23347e | 140 | Specify pre-requisites in Makefile.PL or Build.PL |
f67486be KR |
141 | |
142 | =item * | |
143 | ||
144 | Specify Perl version requirements with C<use> | |
145 | ||
146 | =item * | |
147 | ||
148 | Include tests with your module | |
149 | ||
150 | =item * | |
151 | ||
152 | Choose a sensible and consistent version numbering scheme (X.YY is the common Perl module numbering scheme) | |
153 | ||
154 | =item * | |
155 | ||
156 | Increment the version number for every change, no matter how small | |
157 | ||
158 | =item * | |
159 | ||
160 | Package the module using "make dist" | |
161 | ||
162 | =item * | |
163 | ||
164 | Choose an appropriate license (GPL/Artistic is a good default) | |
165 | ||
166 | =back | |
167 | ||
168 | =head1 BEFORE YOU START WRITING A MODULE | |
169 | ||
170 | Try not to launch headlong into developing your module without spending | |
171 | some time thinking first. A little forethought may save you a vast | |
172 | amount of effort later on. | |
173 | ||
174 | =head2 Has it been done before? | |
175 | ||
176 | You may not even need to write the module. Check whether it's already | |
177 | been done in Perl, and avoid re-inventing the wheel unless you have a | |
178 | good reason. | |
179 | ||
ccbb3b41 | 180 | Good places to look for pre-existing modules include |
4eea8a8b KE |
181 | L<http://search.cpan.org/> and L<https://metacpan.org> |
182 | and asking on C<module-authors@perl.org> | |
183 | (L<http://lists.perl.org/list/module-authors.html>). | |
ccbb3b41 | 184 | |
f67486be KR |
185 | If an existing module B<almost> does what you want, consider writing a |
186 | patch, writing a subclass, or otherwise extending the existing module | |
187 | rather than rewriting it. | |
188 | ||
189 | =head2 Do one thing and do it well | |
190 | ||
191 | At the risk of stating the obvious, modules are intended to be modular. | |
192 | A Perl developer should be able to use modules to put together the | |
193 | building blocks of their application. However, it's important that the | |
194 | blocks are the right shape, and that the developer shouldn't have to use | |
195 | a big block when all they need is a small one. | |
196 | ||
197 | Your module should have a clearly defined scope which is no longer than | |
198 | a single sentence. Can your module be broken down into a family of | |
199 | related modules? | |
200 | ||
201 | Bad example: | |
202 | ||
203 | "FooBar.pm provides an implementation of the FOO protocol and the | |
204 | related BAR standard." | |
205 | ||
206 | Good example: | |
207 | ||
208 | "Foo.pm provides an implementation of the FOO protocol. Bar.pm | |
209 | implements the related BAR protocol." | |
210 | ||
211 | This means that if a developer only needs a module for the BAR standard, | |
212 | they should not be forced to install libraries for FOO as well. | |
213 | ||
214 | =head2 What's in a name? | |
215 | ||
216 | Make sure you choose an appropriate name for your module early on. This | |
217 | will help people find and remember your module, and make programming | |
218 | with your module more intuitive. | |
219 | ||
220 | When naming your module, consider the following: | |
221 | ||
222 | =over 4 | |
223 | ||
224 | =item * | |
225 | ||
226 | Be descriptive (i.e. accurately describes the purpose of the module). | |
227 | ||
228 | =item * | |
229 | ||
230 | Be consistent with existing modules. | |
231 | ||
232 | =item * | |
233 | ||
234 | Reflect the functionality of the module, not the implementation. | |
235 | ||
236 | =item * | |
237 | ||
238 | Avoid starting a new top-level hierarchy, especially if a suitable | |
239 | hierarchy already exists under which you could place your module. | |
240 | ||
241 | =back | |
242 | ||
243 | You should contact modules@perl.org to ask them about your module name | |
244 | before publishing your module. You should also try to ask people who | |
245 | are already familiar with the module's application domain and the CPAN | |
246 | naming system. Authors of similar modules, or modules with similar | |
247 | names, may be a good place to start. | |
248 | ||
249 | =head1 DESIGNING AND WRITING YOUR MODULE | |
250 | ||
251 | Considerations for module design and coding: | |
252 | ||
253 | =head2 To OO or not to OO? | |
254 | ||
255 | Your module may be object oriented (OO) or not, or it may have both kinds | |
256 | of interfaces available. There are pros and cons of each technique, which | |
257 | should be considered when you design your API. | |
258 | ||
325c7616 DR |
259 | In I<Perl Best Practices> (copyright 2004, Published by O'Reilly Media, Inc.), |
260 | Damian Conway provides a list of criteria to use when deciding if OO is the | |
261 | right fit for your problem: | |
f67486be KR |
262 | |
263 | =over 4 | |
264 | ||
995ab4ef | 265 | =item * |
f67486be | 266 | |
325c7616 | 267 | The system being designed is large, or is likely to become large. |
f67486be | 268 | |
995ab4ef | 269 | =item * |
f67486be | 270 | |
325c7616 DR |
271 | The data can be aggregated into obvious structures, especially if |
272 | there's a large amount of data in each aggregate. | |
f67486be | 273 | |
995ab4ef | 274 | =item * |
f67486be | 275 | |
325c7616 DR |
276 | The various types of data aggregate form a natural hierarchy that |
277 | facilitates the use of inheritance and polymorphism. | |
f67486be | 278 | |
995ab4ef | 279 | =item * |
f67486be | 280 | |
325c7616 DR |
281 | You have a piece of data on which many different operations are |
282 | applied. | |
f67486be | 283 | |
995ab4ef | 284 | =item * |
f67486be | 285 | |
325c7616 DR |
286 | You need to perform the same general operations on related types of |
287 | data, but with slight variations depending on the specific type of data | |
288 | the operations are applied to. | |
f67486be | 289 | |
995ab4ef | 290 | =item * |
f67486be | 291 | |
325c7616 | 292 | It's likely you'll have to add new data types later. |
f67486be | 293 | |
995ab4ef | 294 | =item * |
f67486be | 295 | |
325c7616 DR |
296 | The typical interactions between pieces of data are best represented by |
297 | operators. | |
f67486be | 298 | |
995ab4ef | 299 | =item * |
f67486be | 300 | |
325c7616 DR |
301 | The implementation of individual components of the system is likely to |
302 | change over time. | |
f67486be | 303 | |
995ab4ef | 304 | =item * |
f67486be | 305 | |
325c7616 | 306 | The system design is already object-oriented. |
f67486be | 307 | |
995ab4ef | 308 | =item * |
f67486be | 309 | |
325c7616 | 310 | Large numbers of other programmers will be using your code modules. |
f67486be KR |
311 | |
312 | =back | |
313 | ||
314 | Think carefully about whether OO is appropriate for your module. | |
315 | Gratuitous object orientation results in complex APIs which are | |
316 | difficult for the average module user to understand or use. | |
317 | ||
318 | =head2 Designing your API | |
319 | ||
320 | Your interfaces should be understandable by an average Perl programmer. | |
321 | The following guidelines may help you judge whether your API is | |
322 | sufficiently straightforward: | |
323 | ||
324 | =over 4 | |
325 | ||
326 | =item Write simple routines to do simple things. | |
327 | ||
328 | It's better to have numerous simple routines than a few monolithic ones. | |
329 | If your routine changes its behaviour significantly based on its | |
330 | arguments, it's a sign that you should have two (or more) separate | |
331 | routines. | |
332 | ||
333 | =item Separate functionality from output. | |
334 | ||
335 | Return your results in the most generic form possible and allow the user | |
336 | to choose how to use them. The most generic form possible is usually a | |
337 | Perl data structure which can then be used to generate a text report, | |
338 | HTML, XML, a database query, or whatever else your users require. | |
339 | ||
340 | If your routine iterates through some kind of list (such as a list of | |
341 | files, or records in a database) you may consider providing a callback | |
342 | so that users can manipulate each element of the list in turn. | |
343 | File::Find provides an example of this with its | |
344 | C<find(\&wanted, $dir)> syntax. | |
345 | ||
346 | =item Provide sensible shortcuts and defaults. | |
347 | ||
348 | Don't require every module user to jump through the same hoops to achieve a | |
349 | simple result. You can always include optional parameters or routines for | |
350 | more complex or non-standard behaviour. If most of your users have to | |
351 | type a few almost identical lines of code when they start using your | |
352 | module, it's a sign that you should have made that behaviour a default. | |
353 | Another good indicator that you should use defaults is if most of your | |
354 | users call your routines with the same arguments. | |
355 | ||
356 | =item Naming conventions | |
357 | ||
358 | Your naming should be consistent. For instance, it's better to have: | |
359 | ||
360 | display_day(); | |
361 | display_week(); | |
362 | display_year(); | |
363 | ||
364 | than | |
365 | ||
366 | display_day(); | |
367 | week_display(); | |
368 | show_year(); | |
369 | ||
370 | This applies equally to method names, parameter names, and anything else | |
371 | which is visible to the user (and most things that aren't!) | |
372 | ||
373 | =item Parameter passing | |
374 | ||
36923606 | 375 | Use named parameters. It's easier to use a hash like this: |
f67486be KR |
376 | |
377 | $obj->do_something( | |
378 | name => "wibble", | |
379 | type => "text", | |
380 | size => 1024, | |
381 | ); | |
382 | ||
383 | ... than to have a long list of unnamed parameters like this: | |
384 | ||
385 | $obj->do_something("wibble", "text", 1024); | |
386 | ||
387 | While the list of arguments might work fine for one, two or even three | |
388 | arguments, any more arguments become hard for the module user to | |
389 | remember, and hard for the module author to manage. If you want to add | |
390 | a new parameter you will have to add it to the end of the list for | |
391 | backward compatibility, and this will probably make your list order | |
392 | unintuitive. Also, if many elements may be undefined you may see the | |
393 | following unattractive method calls: | |
394 | ||
555bd962 | 395 | $obj->do_something(undef, undef, undef, undef, undef, 1024); |
f67486be KR |
396 | |
397 | Provide sensible defaults for parameters which have them. Don't make | |
398 | your users specify parameters which will almost always be the same. | |
399 | ||
400 | The issue of whether to pass the arguments in a hash or a hashref is | |
401 | largely a matter of personal style. | |
402 | ||
403 | The use of hash keys starting with a hyphen (C<-name>) or entirely in | |
404 | upper case (C<NAME>) is a relic of older versions of Perl in which | |
405 | ordinary lower case strings were not handled correctly by the C<=E<gt>> | |
406 | operator. While some modules retain uppercase or hyphenated argument | |
407 | keys for historical reasons or as a matter of personal style, most new | |
408 | modules should use simple lower case keys. Whatever you choose, be | |
409 | consistent! | |
410 | ||
411 | =back | |
412 | ||
413 | =head2 Strictness and warnings | |
414 | ||
415 | Your module should run successfully under the strict pragma and should | |
416 | run without generating any warnings. Your module should also handle | |
417 | taint-checking where appropriate, though this can cause difficulties in | |
418 | many cases. | |
419 | ||
420 | =head2 Backwards compatibility | |
421 | ||
422 | Modules which are "stable" should not break backwards compatibility | |
423 | without at least a long transition phase and a major change in version | |
424 | number. | |
425 | ||
426 | =head2 Error handling and messages | |
427 | ||
428 | When your module encounters an error it should do one or more of: | |
429 | ||
430 | =over 4 | |
431 | ||
432 | =item * | |
433 | ||
434 | Return an undefined value. | |
435 | ||
436 | =item * | |
437 | ||
438 | set C<$Module::errstr> or similar (C<errstr> is a common name used by | |
439 | DBI and other popular modules; if you choose something else, be sure to | |
440 | document it clearly). | |
441 | ||
442 | =item * | |
443 | ||
444 | C<warn()> or C<carp()> a message to STDERR. | |
445 | ||
446 | =item * | |
447 | ||
448 | C<croak()> only when your module absolutely cannot figure out what to | |
449 | do. (C<croak()> is a better version of C<die()> for use within | |
450 | modules, which reports its errors from the perspective of the caller. | |
451 | See L<Carp> for details of C<croak()>, C<carp()> and other useful | |
452 | routines.) | |
453 | ||
454 | =item * | |
455 | ||
456 | As an alternative to the above, you may prefer to throw exceptions using | |
457 | the Error module. | |
458 | ||
459 | =back | |
460 | ||
461 | Configurable error handling can be very useful to your users. Consider | |
462 | offering a choice of levels for warning and debug messages, an option to | |
463 | send messages to a separate file, a way to specify an error-handling | |
464 | routine, or other such features. Be sure to default all these options | |
465 | to the commonest use. | |
466 | ||
467 | =head1 DOCUMENTING YOUR MODULE | |
468 | ||
469 | =head2 POD | |
470 | ||
471 | Your module should include documentation aimed at Perl developers. | |
472 | You should use Perl's "plain old documentation" (POD) for your general | |
473 | technical documentation, though you may wish to write additional | |
474 | documentation (white papers, tutorials, etc) in some other format. | |
475 | You need to cover the following subjects: | |
476 | ||
477 | =over 4 | |
478 | ||
479 | =item * | |
480 | ||
481 | A synopsis of the common uses of the module | |
482 | ||
483 | =item * | |
484 | ||
485 | The purpose, scope and target applications of your module | |
486 | ||
487 | =item * | |
488 | ||
489 | Use of each publically accessible method or subroutine, including | |
490 | parameters and return values | |
491 | ||
492 | =item * | |
493 | ||
494 | Examples of use | |
495 | ||
496 | =item * | |
497 | ||
498 | Sources of further information | |
499 | ||
500 | =item * | |
501 | ||
502 | A contact email address for the author/maintainer | |
503 | ||
504 | =back | |
505 | ||
506 | The level of detail in Perl module documentation generally goes from | |
507 | less detailed to more detailed. Your SYNOPSIS section should contain a | |
508 | minimal example of use (perhaps as little as one line of code; skip the | |
da75cd15 | 509 | unusual use cases or anything not needed by most users); the |
f67486be KR |
510 | DESCRIPTION should describe your module in broad terms, generally in |
511 | just a few paragraphs; more detail of the module's routines or methods, | |
512 | lengthy code examples, or other in-depth material should be given in | |
513 | subsequent sections. | |
514 | ||
515 | Ideally, someone who's slightly familiar with your module should be able | |
516 | to refresh their memory without hitting "page down". As your reader | |
517 | continues through the document, they should receive a progressively | |
518 | greater amount of knowledge. | |
519 | ||
520 | The recommended order of sections in Perl module documentation is: | |
521 | ||
522 | =over 4 | |
523 | ||
524 | =item * | |
525 | ||
526 | NAME | |
527 | ||
528 | =item * | |
529 | ||
530 | SYNOPSIS | |
531 | ||
532 | =item * | |
533 | ||
534 | DESCRIPTION | |
535 | ||
536 | =item * | |
537 | ||
538 | One or more sections or subsections giving greater detail of available | |
539 | methods and routines and any other relevant information. | |
540 | ||
541 | =item * | |
542 | ||
543 | BUGS/CAVEATS/etc | |
544 | ||
545 | =item * | |
546 | ||
547 | AUTHOR | |
548 | ||
549 | =item * | |
550 | ||
551 | SEE ALSO | |
552 | ||
553 | =item * | |
554 | ||
555 | COPYRIGHT and LICENSE | |
556 | ||
557 | =back | |
558 | ||
559 | Keep your documentation near the code it documents ("inline" | |
560 | documentation). Include POD for a given method right above that | |
561 | method's subroutine. This makes it easier to keep the documentation up | |
562 | to date, and avoids having to document each piece of code twice (once in | |
563 | POD and once in comments). | |
564 | ||
565 | =head2 README, INSTALL, release notes, changelogs | |
566 | ||
567 | Your module should also include a README file describing the module and | |
568 | giving pointers to further information (website, author email). | |
569 | ||
570 | An INSTALL file should be included, and should contain simple installation | |
36923606 | 571 | instructions. When using ExtUtils::MakeMaker this will usually be: |
ff23347e JB |
572 | |
573 | =over 4 | |
574 | ||
575 | =item perl Makefile.PL | |
576 | ||
577 | =item make | |
578 | ||
579 | =item make test | |
580 | ||
581 | =item make install | |
582 | ||
583 | =back | |
584 | ||
585 | When using Module::Build, this will usually be: | |
586 | ||
587 | =over 4 | |
588 | ||
589 | =item perl Build.PL | |
590 | ||
591 | =item perl Build | |
592 | ||
593 | =item perl Build test | |
594 | ||
595 | =item perl Build install | |
596 | ||
597 | =back | |
f67486be KR |
598 | |
599 | Release notes or changelogs should be produced for each release of your | |
600 | software describing user-visible changes to your module, in terms | |
601 | relevant to the user. | |
602 | ||
4a8dd740 NB |
603 | Unless you have good reasons for using some other format |
604 | (for example, a format used within your company), | |
605 | the convention is to name your changelog file C<Changes>, | |
606 | and to follow the simple format described in L<CPAN::Changes::Spec>. | |
607 | ||
f67486be KR |
608 | =head1 RELEASE CONSIDERATIONS |
609 | ||
610 | =head2 Version numbering | |
611 | ||
612 | Version numbers should indicate at least major and minor releases, and | |
613 | possibly sub-minor releases. A major release is one in which most of | |
614 | the functionality has changed, or in which major new functionality is | |
615 | added. A minor release is one in which a small amount of functionality | |
616 | has been added or changed. Sub-minor version numbers are usually used | |
617 | for changes which do not affect functionality, such as documentation | |
618 | patches. | |
619 | ||
620 | The most common CPAN version numbering scheme looks like this: | |
621 | ||
622 | 1.00, 1.10, 1.11, 1.20, 1.30, 1.31, 1.32 | |
623 | ||
624 | A correct CPAN version number is a floating point number with at least | |
36923606 | 625 | 2 digits after the decimal. You can test whether it conforms to CPAN by |
f67486be KR |
626 | using |
627 | ||
628 | perl -MExtUtils::MakeMaker -le 'print MM->parse_version(shift)' 'Foo.pm' | |
629 | ||
4398853c A |
630 | If you want to release a 'beta' or 'alpha' version of a module but |
631 | don't want CPAN.pm to list it as most recent use an '_' after the | |
36923606 | 632 | regular version number followed by at least 2 digits, eg. 1.20_01. If |
4398853c A |
633 | you do this, the following idiom is recommended: |
634 | ||
fbff26bc FC |
635 | our $VERSION = "1.12_01"; # so CPAN distribution will have |
636 | # right filename | |
69520e41 | 637 | our $XS_VERSION = $VERSION; # only needed if you have XS code |
fbff26bc FC |
638 | $VERSION = eval $VERSION; # so "use Module 0.002" won't warn on |
639 | # underscore | |
4398853c A |
640 | |
641 | With that trick MakeMaker will only read the first line and thus read | |
642 | the underscore, while the perl interpreter will evaluate the $VERSION | |
36923606 | 643 | and convert the string into a number. Later operations that treat |
4398853c A |
644 | $VERSION as a number will then be able to do so without provoking a |
645 | warning about $VERSION not being a number. | |
f67486be KR |
646 | |
647 | Never release anything (even a one-word documentation patch) without | |
648 | incrementing the number. Even a one-word documentation patch should | |
649 | result in a change in version at the sub-minor level. | |
650 | ||
69520e41 | 651 | Once picked, it is important to stick to your version scheme, without |
36923606 | 652 | reducing the number of digits. This is because "downstream" packagers, |
69520e41 | 653 | such as the FreeBSD ports system, interpret the version numbers in |
36923606 | 654 | various ways. If you change the number of digits in your version scheme, |
69520e41 E |
655 | you can confuse these systems so they get the versions of your module |
656 | out of order, which is obviously bad. | |
657 | ||
f67486be KR |
658 | =head2 Pre-requisites |
659 | ||
660 | Module authors should carefully consider whether to rely on other | |
661 | modules, and which modules to rely on. | |
662 | ||
663 | Most importantly, choose modules which are as stable as possible. In | |
664 | order of preference: | |
665 | ||
666 | =over 4 | |
667 | ||
668 | =item * | |
669 | ||
670 | Core Perl modules | |
671 | ||
672 | =item * | |
673 | ||
674 | Stable CPAN modules | |
675 | ||
676 | =item * | |
677 | ||
678 | Unstable CPAN modules | |
679 | ||
680 | =item * | |
681 | ||
682 | Modules not available from CPAN | |
683 | ||
684 | =back | |
685 | ||
686 | Specify version requirements for other Perl modules in the | |
ff23347e | 687 | pre-requisites in your Makefile.PL or Build.PL. |
f67486be | 688 | |
ff23347e | 689 | Be sure to specify Perl version requirements both in Makefile.PL or |
36923606 | 690 | Build.PL and with C<require 5.6.1> or similar. See the section on |
ff23347e | 691 | C<use VERSION> of L<perlfunc/require> for details. |
f67486be KR |
692 | |
693 | =head2 Testing | |
694 | ||
ff23347e | 695 | All modules should be tested before distribution (using "make disttest"), |
f67486be KR |
696 | and the tests should also be available to people installing the modules |
697 | (using "make test"). | |
ff23347e | 698 | For Module::Build you would use the C<make test> equivalent C<perl Build test>. |
f67486be KR |
699 | |
700 | The importance of these tests is proportional to the alleged stability of a | |
36923606 FC |
701 | module. A module which purports to be |
702 | stable or which hopes to achieve wide | |
f67486be KR |
703 | use should adhere to as strict a testing regime as possible. |
704 | ||
705 | Useful modules to help you write tests (with minimum impact on your | |
706 | development process or your time) include Test::Simple, Carp::Assert | |
707 | and Test::Inline. | |
ff23347e | 708 | For more sophisticated test suites there are Test::More and Test::MockObject. |
f67486be KR |
709 | |
710 | =head2 Packaging | |
711 | ||
ff23347e JB |
712 | Modules should be packaged using one of the standard packaging tools. |
713 | Currently you have the choice between ExtUtils::MakeMaker and the | |
714 | more platform independent Module::Build, allowing modules to be installed in a | |
715 | consistent manner. | |
716 | When using ExtUtils::MakeMaker, you can use "make dist" to create your | |
36923606 FC |
717 | package. Tools exist to help you to build your module in a |
718 | MakeMaker-friendly style. These include ExtUtils::ModuleMaker and h2xs. | |
719 | See also L<perlnewmod>. | |
f67486be KR |
720 | |
721 | =head2 Licensing | |
722 | ||
723 | Make sure that your module has a license, and that the full text of it | |
724 | is included in the distribution (unless it's a common one and the terms | |
725 | of the license don't require you to include it). | |
726 | ||
727 | If you don't know what license to use, dual licensing under the GPL | |
728 | and Artistic licenses (the same as Perl itself) is a good idea. | |
2a551100 | 729 | See L<perlgpl> and L<perlartistic>. |
f67486be KR |
730 | |
731 | =head1 COMMON PITFALLS | |
732 | ||
733 | =head2 Reinventing the wheel | |
734 | ||
735 | There are certain application spaces which are already very, very well | |
736 | served by CPAN. One example is templating systems, another is date and | |
737 | time modules, and there are many more. While it is a rite of passage to | |
738 | write your own version of these things, please consider carefully | |
739 | whether the Perl world really needs you to publish it. | |
740 | ||
741 | =head2 Trying to do too much | |
742 | ||
743 | Your module will be part of a developer's toolkit. It will not, in | |
744 | itself, form the B<entire> toolkit. It's tempting to add extra features | |
745 | until your code is a monolithic system rather than a set of modular | |
746 | building blocks. | |
747 | ||
748 | =head2 Inappropriate documentation | |
749 | ||
750 | Don't fall into the trap of writing for the wrong audience. Your | |
751 | primary audience is a reasonably experienced developer with at least | |
752 | a moderate understanding of your module's application domain, who's just | |
753 | downloaded your module and wants to start using it as quickly as possible. | |
754 | ||
755 | Tutorials, end-user documentation, research papers, FAQs etc are not | |
756 | appropriate in a module's main documentation. If you really want to | |
757 | write these, include them as sub-documents such as C<My::Module::Tutorial> or | |
758 | C<My::Module::FAQ> and provide a link in the SEE ALSO section of the | |
759 | main documentation. | |
760 | ||
761 | =head1 SEE ALSO | |
762 | ||
763 | =over 4 | |
764 | ||
765 | =item L<perlstyle> | |
766 | ||
767 | General Perl style guide | |
768 | ||
769 | =item L<perlnewmod> | |
770 | ||
771 | How to create a new module | |
772 | ||
773 | =item L<perlpod> | |
774 | ||
775 | POD documentation | |
776 | ||
777 | =item L<podchecker> | |
778 | ||
779 | Verifies your POD's correctness | |
780 | ||
ff23347e JB |
781 | =item Packaging Tools |
782 | ||
783 | L<ExtUtils::MakeMaker>, L<Module::Build> | |
784 | ||
f67486be KR |
785 | =item Testing tools |
786 | ||
ff23347e | 787 | L<Test::Simple>, L<Test::Inline>, L<Carp::Assert>, L<Test::More>, L<Test::MockObject> |
f67486be KR |
788 | |
789 | =item http://pause.perl.org/ | |
790 | ||
791 | Perl Authors Upload Server. Contains links to information for module | |
792 | authors. | |
793 | ||
794 | =item Any good book on software engineering | |
795 | ||
796 | =back | |
797 | ||
798 | =head1 AUTHOR | |
799 | ||
800 | Kirrily "Skud" Robert <skud@cpan.org> | |
801 |