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48cb5b3a 1=head1 NAME
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3perlpolicy - Various and sundry policies and commitments related to the perl core
4
5=head1 DESCRIPTION
6
7This document is the master document which records all written
8policies about how the Perl 5 Porters collectively develop and maintain
9the Perl core.
10
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11=head1 MAINTENANCE AND SUPPORT
12
13Perl 5 is developed by a community, not a corporate entity. Every change
14contributed to the Perl core is the result of a donation. Typically, these
15donations are contributions of code or time by individual members of our
16community. On occasion, these donations come in the form of corporate
17or organizational sponsorship of a particular individual or project.
18
19As a volunteer organization, the commitments we make are heavily dependent
20on the goodwill and hard work of individuals who have no obligation to
21contribute to Perl.
22
3b4ebcde 23That being said, we value Perl's stability and security and have long
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24had an unwritten covenant with the broader Perl community to support
25and maintain releases of Perl.
26
27This document codifies the support and maintenance commitments that
28the Perl community should expect from Perl's developers:
29
30=over
31
32=item *
33
34We "officially" support the two most recent stable release
35series'. As of the release of 5.14.0, we will "officially"
36end support for Perl 5.10, other than providing security
37updates as described below.
38
39=item *
40
41To the best of our ability, we will attempt to fix critical issues
7fdd8d84 42in the two most recent stable 5.x release series'. Fixes for the
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43current release series take precedence over fixes for the previous
44release series.
45
46=item *
47
48To the best of our ability, we will provide "critical" security patches
49/ releases for any major version of Perl initially released within the
50past three years. We can only commit to providing these for the most
51recent .y release in any 5.x.y series.
52
53=item *
54
55We will not provide security updates or bug fixes for development
56releases of Perl.
57
58=item *
59
60We encourage vendors to ship the most recent supported release of
61Perl at the time of their code freeze.
62
63=item *
64
65As a vendor, you may have a requirement to backport security fixes
66beyond our 3 year support commitment. We can provide limited support and
67advice to you as you do so and, where possible will try to apply
68those patches to the relevant -maint branches in git, though we may or
69may not choose to make numbered releases or "official" patches
70available. Contact us at E<lt>perl5-security-report@perl.orgE<gt>
71to begin that process.
72
73=back
74
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75=head1 BACKWARD COMPATIBILITY AND DEPRECATION
76
77Our community has a long-held belief that backward-compatibility is a
78virtue, even when the functionality in question is a design flaw.
79
80We would all love to unmake some mistakes we've made over the past
81decades. Living with every design error we've ever made can lead
82to painful stagnation. Unwinding our mistakes is very, very
83difficult. Doing so without actively harming our users is
84nearly impossible.
85
86Lately, ignoring or actively opposing compatibility with earlier versions
87of Perl has come into vogue. Sometimes, a change is proposed which
88wants to usurp syntax which previously had another meaning. Sometimes,
339a461d 89a change wants to improve previously-crazy semantics.
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90
91Down this road lies madness.
92
93Requiring end-user programmers to change just a few language constructs,
94even language constructs which no well-educated developer would ever
95intentionally use is tantamount to saying "you should not upgrade to
96a new release of Perl unless you have 100% test coverage and can do a
97full manual audit of your codebase." If we were to have tools capable of
98reliably upgrading Perl source code from one version of Perl to another,
99this concern could be significantly mitigated.
100
101We want to ensure that Perl continues to grow and flourish in the coming
102years and decades, but not at the expense of our user community.
103
104Existing syntax and semantics should only be marked for destruction in
105very limited circumstances. If a given language feature's continued
106inclusion in the language will cause significant harm to the language
107or prevent us from making needed changes to the runtime, then it may
108be considered for deprecation.
109
110Any language change which breaks backward-compatibility should be able to
111be enabled or disabled lexically. Unless code at a given scope declares
112that it wants the new behavior, that new behavior should be disabled.
113Which backward-incompatible changes are controlled implicitly by a
114'use v5.x.y' is a decision which should be made by the pumpking in
115consultation with the community.
116
117When a backward-incompatible change can't be toggled lexically, the decision
118to change the language must be considered very, very carefully. If it's
119possible to move the old syntax or semantics out of the core language
120and into XS-land, that XS module should be enabled by default unless
121the user declares that they want a newer revision of Perl.
122
123Historically, we've held ourselves to a far higher standard than
124backward-compatibility -- bugward-compatibility. Any accident of
125implementation or unintentional side-effect of running some bit of code
126has been considered to be a feature of the language to be defended with
127the same zeal as any other feature or functionality. No matter how
128frustrating these unintentional features may be to us as we continue
129to improve Perl, these unintentional features often deserve our
130protection. It is very important that existing software written in
131Perl continue to work correctly. If end-user developers have adopted a
132bug as a feature, we need to treat it as such.
133
134New syntax and semantics which don't break existing language constructs
135and syntax have a much lower bar. They merely need to prove themselves
136to be useful, elegant, well designed and well tested.
137
138=head2 Terminology
139
140To make sure we're talking about the same thing when we discuss the removal
141of features or functionality from the Perl core, we have specific definitions
142for a few words and phrases.
143
144=over
145
146=item experimental
147
148If something in the Perl core is marked as B<experimental>, we may change
149its behaviour, deprecate or remove it without notice. While we'll always
150do our best to smooth the transition path for users of experimental
151features, you should contact the perl5-porters mailinglist if you find
152an experimental feature useful and want to help shape its future.
153
154=item deprecated
155
156If something in the Perl core is marked as B<deprecated>, we may remove it
3b4ebcde 157from the core in the next stable release series, though we may not. As of
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158Perl 5.12, deprecated features and modules warn the user as they're used.
159If you use a deprecated feature and believe that its removal from the Perl
160core would be a mistake, please contact the perl5-porters mailinglist and
161plead your case. We don't deprecate things without a good reason, but
162sometimes there's a counterargument we haven't considered. Historically,
163we did not distinguish between "deprecated" and "discouraged" features.
164
165=item discouraged
166
167From time to time, we may mark language constructs and features which we
168consider to have been mistakes as B<discouraged>. Discouraged features
169aren't candidates for removal in the next major release series, but
170we may later deprecate them if they're found to stand in the way of a
171significant improvement to the core.
172
173=item removed
174
175Once a feature, construct or module has been marked as deprecated for a
176stable release cycle, we may remove it from the core. Unsurprisingly,
177we say we've B<removed> these things.
178
179=back
48cb5b3a 180
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181=head1 MAINTENANCE BRANCHES
182
183=over
184
185=item *
186
187New releases of maint should contain as few changes as possible.
188If there is any question about whether a given patch might merit
189inclusion in a maint release, then it almost certainly should not
190be included.
191
192=item *
193
194Portability fixes, such as changes to Configure and the files in
195hints/ are acceptable. Ports of Perl to a new platform, architecture
196or OS release that involve changes to the implementation are NOT
197acceptable.
198
199=item *
200
201Documentation updates are acceptable.
202
203=item *
204
205Patches that add new warnings or errors or deprecate features
206are not acceptable.
207
208=item *
209
210Patches that fix crashing bugs that do not otherwise change Perl's
211functionality or negatively impact performance are acceptable.
212
213=item *
214
215Patches that fix CVEs or security issues are acceptable, but should
216be run through the perl5-security-report@perl.org mailing list
217rather than applied directly.
218
219=item *
220
221Updates to dual-life modules should consist of minimal patches to
222fix crashing or security issues (as above).
223
224=item *
225
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226Minimal patches that fix platform-specific test failures or
227installation issues are acceptable. When these changes are made
228to dual-life modules for which CPAN is canonical, any changes
229should be coordinated with the upstream author.
230
231=item *
232
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233New versions of dual-life modules should NOT be imported into maint.
234Those belong in the next stable series.
235
236=item *
237
238Patches that add or remove features are not acceptable.
239
240=item *
241
242Patches that break binary compatibility are not acceptable. (Please
243talk to a pumpking.)
244
245=back
246
247
248=head2 Getting changes into a maint branch
249
250Historically, only the pumpking cherry-picked changes from bleadperl
251into maintperl. This has...scaling problems. At the same time,
252maintenance branches of stable versions of Perl need to be treated with
253great care. To that end, we're going to try out a new process for
254maint-5.12.
255
256Any committer may cherry-pick any commit from blead to maint-5.12 if
257they send mail to perl5-porters announcing their intent to cherry-pick
258a specific commit along with a rationale for doing so and at least two
259other committers respond to the list giving their assent. (This policy
260applies to current and former pumpkings, as well as other committers.)
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261
262=head1 CONTRIBUTED MODULES
263
264
265=head2 A Social Contract about Artistic Control
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266
267What follows is a statement about artistic control, defined as the ability
268of authors of packages to guide the future of their code and maintain
269control over their work. It is a recognition that authors should have
270control over their work, and that it is a responsibility of the rest of
271the Perl community to ensure that they retain this control. It is an
272attempt to document the standards to which we, as Perl developers, intend
273to hold ourselves. It is an attempt to write down rough guidelines about
274the respect we owe each other as Perl developers.
275
276This statement is not a legal contract. This statement is not a legal
277document in any way, shape, or form. Perl is distributed under the GNU
278Public License and under the Artistic License; those are the precise legal
279terms. This statement isn't about the law or licenses. It's about
280community, mutual respect, trust, and good-faith cooperation.
281
282We recognize that the Perl core, defined as the software distributed with
283the heart of Perl itself, is a joint project on the part of all of us.
aaa2bbb1 284From time to time, a script, module, or set of modules (hereafter referred
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285to simply as a "module") will prove so widely useful and/or so integral to
286the correct functioning of Perl itself that it should be distributed with
287Perl core. This should never be done without the author's explicit
288consent, and a clear recognition on all parts that this means the module
289is being distributed under the same terms as Perl itself. A module author
290should realize that inclusion of a module into the Perl core will
291necessarily mean some loss of control over it, since changes may
292occasionally have to be made on short notice or for consistency with the
293rest of Perl.
294
295Once a module has been included in the Perl core, however, everyone
296involved in maintaining Perl should be aware that the module is still the
297property of the original author unless the original author explicitly
298gives up their ownership of it. In particular:
299
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300=over
301
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302=item *
303
304The version of the module in the core should still be considered the
305work of the original author. All patches, bug reports, and so
306forth should be fed back to them. Their development directions
307should be respected whenever possible.
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309=item *
310
311Patches may be applied by the pumpkin holder without the explicit
312cooperation of the module author if and only if they are very minor,
313time-critical in some fashion (such as urgent security fixes), or if
314the module author cannot be reached. Those patches must still be
315given back to the author when possible, and if the author decides on
316an alternate fix in their version, that fix should be strongly
317preferred unless there is a serious problem with it. Any changes not
318endorsed by the author should be marked as such, and the contributor
319of the change acknowledged.
320
321=item *
322
323The version of the module distributed with Perl should, whenever
324possible, be the latest version of the module as distributed by the
325author (the latest non-beta version in the case of public Perl
326releases), although the pumpkin holder may hold off on upgrading the
327version of the module distributed with Perl to the latest version
328until the latest version has had sufficient testing.
329
330=back
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331
332In other words, the author of a module should be considered to have final
333say on modifications to their module whenever possible (bearing in mind
334that it's expected that everyone involved will work together and arrive at
335reasonable compromises when there are disagreements).
336
337As a last resort, however:
338
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339
340If the author's vision of the future of their module is sufficiently
341different from the vision of the pumpkin holder and perl5-porters as a
342whole so as to cause serious problems for Perl, the pumpkin holder may
343choose to formally fork the version of the module in the core from the
344one maintained by the author. This should not be done lightly and
c4f5d98d 345should B<always> if at all possible be done only after direct input
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346from Larry. If this is done, it must then be made explicit in the
347module as distributed with Perl core that it is a forked version and
348that while it is based on the original author's work, it is no longer
349maintained by them. This must be noted in both the documentation and
350in the comments in the source of the module.
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351
352Again, this should be a last resort only. Ideally, this should never
353happen, and every possible effort at cooperation and compromise should be
354made before doing this. If it does prove necessary to fork a module for
355the overall health of Perl, proper credit must be given to the original
356author in perpetuity and the decision should be constantly re-evaluated to
357see if a remerging of the two branches is possible down the road.
358
359In all dealings with contributed modules, everyone maintaining Perl should
360keep in mind that the code belongs to the original author, that they may
361not be on perl5-porters at any given time, and that a patch is not
362official unless it has been integrated into the author's copy of the
363module. To aid with this, and with points #1, #2, and #3 above, contact
364information for the authors of all contributed modules should be kept with
365the Perl distribution.
366
367Finally, the Perl community as a whole recognizes that respect for
368ownership of code, respect for artistic control, proper credit, and active
369effort to prevent unintentional code skew or communication gaps is vital
370to the health of the community and Perl itself. Members of a community
371should not normally have to resort to rules and laws to deal with each
372other, and this document, although it contains rules so as to be clear, is
373about an attitude and general approach. The first step in any dispute
374should be open communication, respect for opposing views, and an attempt
375at a compromise. In nearly every circumstance nothing more will be
376necessary, and certainly no more drastic measure should be used until
377every avenue of communication and discussion has failed.
3c78fafa 378
70e4a83b 379
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380=head1 DOCUMENTATION
381
382Perl's documentation is an important resource for our users. It's
383incredibly important for Perl's documentation to be reasonably coherent
384and to accurately reflect the current implementation.
385
386Just as P5P collectively maintains the codebase, we collectively
387maintain the documentation. Writing a particular bit of documentation
388doesn't give an author control of the future of that documentation.
389At the same time, just as source code changes should match the style
390of their surrounding blocks, so should documentation changes.
391
392Examples in documentation should be illustrative of the concept
393they're explaining. Sometimes, the best way to show how a
394language feature works is with a small program the reader can
395run without modification. More often, examples will consist
396of a snippet of code containing only the "important" bits.
397The definition of "important" varies from snippet to snippet.
1bb8a155 398Sometimes it's important to declare C<use strict> and C<use warnings>,
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399initialize all variables and fully catch every error condition.
400More often than not, though, those things obscure the lesson
401the example was intended to teach.
402
403As Perl is developed by a global team of volunteers, our
404documentation often contains spellings which look funny
405to I<somebody>. Choice of American/British/Other spellings
406is left as an exercise for the author of each bit of
407documentation. When patching documentation, try to emulate
408the documentation around you, rather than changing the existing
409prose.
410
411In general, documentation should describe what Perl does "now" rather
412than what it used to do. It's perfectly reasonable to include notes
413in documentation about how behaviour has changed from previous releases,
9e9fdd5d 414but, with very few exceptions, documentation isn't "dual-life" --
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415it doesn't need to fully describe how all old versions used to work.
416
417
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418=head1 CREDITS
419
3b4ebcde 420"Social Contract about Contributed Modules" originally by Russ Allbery E<lt>rra@stanford.eduE<gt> and the perl5-porters.
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