doc/plugins/po.mdwn



[[!template id=plugin name=po core=0 author="[[intrigeri]]"]]
[[!tag type/format]]
This plugin adds support for multi-lingual wikis, translated with
gettext, using po4a.
It depends on the Perl Locale::Po4a::Po library (apt-get install po4a).
As detailed bellow in the security section, po4a is subject to
denial-of-service attacks before version 0.35.
[[!toc levels=2]]
Introduction
A language is chosen as the "master" one, and any other supported
language is a "slave" one.
A page written in the "master" language is a "master" page. It can be
of any page type supported by ikiwiki, except po. It does not have to be
named a special way: migration to this plugin does not imply any page
renaming work.
Example: bla/page.mdwn is a "master" Markdown page written in
English; if usedirs is enabled, it is rendered as
bla/page/index.en.html, else as bla/page.en.html.
Any translation of a "master" page into a "slave" language is called
a "slave" page; it is written in the gettext PO format. po is now
a page type supported by ikiwiki.
Example: bla/page.fr.po is the PO "message catalog" used to
translate bla/page.mdwn into French; if usedirs is enabled, it is
rendered as bla/page/index.fr.html, else as bla/page.fr.html
(In)Compatibility
This plugin does not support the indexpages mode. If you don't know
what it is, you probably don't care.
Configuration
Supported languages
po_master_language is used to set the "master" language in
ikiwiki.setup, such as:
    po_master_language => { 'code' => 'en', 'name' => 'English' }

po_slave_languages is used to set the list of supported "slave"
languages, such as:
    po_slave_languages => [ 'fr|Français',
                            'es|Español',
                            'de|Deutsch',
    ]

Decide which pages are translatable
The po_translatable_pages setting configures what pages are
translatable. It is a [[ikiwiki/PageSpec]], so you have lots of
control over what kind of pages are translatable.
The .po files are not considered as being translatable, so you don't need to
worry about excluding them explicitly from this [[ikiwiki/PageSpec]].
Internal links
Links targets
The po_link_to option in ikiwiki.setup is used to decide how
internal links should be generated, depending on web server features
and site-specific preferences.
Default linking behavior
If po_link_to is unset, or set to default, ikiwiki's default
linking behavior is preserved: \[[destpage]] links to the master
language's page.
Link to current language
If po_link_to is set to current, \[[destpage]] links to the
destpage's version written in the current page's language, if
available, i.e.:

foo/destpage/index.LL.html if usedirs is enabled
foo/destpage.LL.html if usedirs is disabled

Link to negotiated language
If po_link_to is set to negotiated, \[[page]] links to the
negotiated preferred language, i.e. foo/page/.
(In)compatibility notes:

if usedirs is disabled, it does not make sense to set po_link_to
to negotiated; this option combination is neither implemented
nor allowed.
if the web server does not support Content Negotiation, setting
po_link_to to negotiated will produce a unusable website.

Server support
Apache
Using Apache mod_negotiation makes it really easy to have Apache
serve any page in the client's preferred language, if available.
Add 'Options MultiViews' to the wiki directory's configuration in Apache.
When usedirs is enabled, one has to set DirectoryIndex index for
the wiki context.
Setting DefaultLanguage LL (replace LL with your default MIME
language code) for the wiki context can help to ensure
bla/page/index.en.html is served as Content-Language: LL.
For details, see Apache's documentation.
lighttpd
Recent versions of lighttpd should be able to use
$HTTP["language"] to configure the translated pages to be served.
See Lighttpd Issue
TODO: Example
Usage
Templates
When po_link_to is not set to negotiated, one should replace some
occurrences of BASEURL with HOMEPAGEURL to get correct links to
the wiki homepage.
The ISTRANSLATION and ISTRANSLATABLE variables can be used to
display things only on translatable or translation pages.
Display page's versions in other languages
The OTHERLANGUAGES loop provides ways to display other languages'
versions of the same page, and the translations' status.
An example of its use can be found in the default
templates/page.tmpl. In case you want to customize it, the following
variables are available inside the loop (for every page in):

URL - url to the page
CODE - two-letters language code
LANGUAGE - language name (as defined in po_slave_languages)
MASTER - is true (1) if, and only if the page is a "master" page
PERCENT - for "slave" pages, is set to the translation completeness, in percents

Display the current translation status
The PERCENTTRANSLATED variable is set to the translation
completeness, expressed in percent, on "slave" pages. It is used by
the default templates/page.tmpl.
Additional PageSpec tests
This plugin enhances the regular [[ikiwiki/PageSpec]] syntax with some
additional tests that are documented [[here|ikiwiki/pagespec/po]].
Automatic PO file update
Committing changes to a "master" page:

updates the POT file and the PO files for the "slave" languages;
the updated PO files are then put under version control;
triggers a refresh of the corresponding HTML slave pages.

Also, when the plugin has just been enabled, or when a page has just
been declared as being translatable, the needed POT and PO files are
created, and the PO files are checked into version control.
Discussion pages and other sub-pages
Discussion should happen in the language in which the pages are
written for real, i.e. the "master" one. If discussion pages are
enabled, "slave" pages therefore link to the "master" page's
discussion page.
Likewise, "slave" pages are not supposed to have sub-pages;
[[WikiLinks|ikiwiki/wikilink]] that appear on a "slave" page therefore link to
the master page's sub-pages.
Translating
One can edit the PO files using ikiwiki's CGI (a message-by-message
interface could also be implemented at some point).
If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's
preferred $EDITOR, without needing to be online.
Markup languages support
[[Markdown|mdwn]] and [[html]] are well supported. Some other markup
languages supported by ikiwiki mostly work, but some pieces of syntax
are not rendered correctly on the slave pages:

[[reStructuredText|rst]]: anonymous hyperlinks and internal
cross-references
[[wikitext]]: conversion of newlines to paragraphs
[[creole]]: verbatim text is wrapped, tables are broken
LaTeX: not supported yet; the dedicated po4a module
could be used to support it, but it would need a security audit
other markup languages have not been tested.

Security
[[po/discussion]] contains a detailed security analysis of this plugin
and its dependencies.
When using po4a older than 0.35, it is recommended to uninstall
Text::WrapI18N (Debian package libtext-wrapi18n-perl), in order to
avoid a potential denial of service.
BUGS
[[!inline pages="bugs/po:* and !bugs/done and !link(bugs/done) and !bugs//"
feeds=no actions=no archive=yes show=0]]
TODO
[[!inline pages="todo/po:* and !todo/done and !link(todo/done) and !todo//"
feeds=no actions=no archive=yes show=0]]
broken links to translatable basewiki pages that lack po files
If a page is not translated yet, the "translated" version of it
displays wikilinks to other, existing (but not yet translated?)
pages as edit links, as if those pages do not exist.
That's really confusing, especially as clicking such a link
brings up an edit form to create a new, english page.
This is with po_link_to=current or negotiated. With default, it doesn't
happen..
Also, this may only happen if the page being linked to is coming from an
underlay, and the underlays lack translation to a given language.
--[[Joey]]

Any simple testcase to reproduce it, please? I've never seen this
happen yet. --[[intrigeri]]


Sure, go here http://l10n.ikiwiki.info/smiley/smileys/index.sv.html
(Currently 0% translateed) and see the 'WikiLink' link at the bottom,
which goes to http://l10n.ikiwiki.info/ikiwiki.cgi?page=ikiwiki/wikilink&from=smiley/smileys&do=create
Compare with eg, the 100% translated Dansk version, where
the WikiLink link links to the English WikiLink page. --[[Joey]]


Seems not related to the page/string translation status: the 0%
translated Spanish version has the correct link, just like the
Dansk version => I'm changing the bug title accordingly.
I tested forcing the sv html page to be rebuilt by translating a
string in it, it did not fix the bug. I did the same for the
Spanish page, it did not introduce the bug. So this is really
weird.
The smiley underlay seems to be the only place where the wrong
thing happens: the basewiki underlay has similar examples
that do not exhibit this bug. An underlay linking to another might
be necessary to reproduce it. Going to dig deeper. --[[intrigeri]]


After a few hours lost in the Perl debugger, I think I have found
the root cause of the problem: in l10n wiki's configured
underlaydir, the basewiki is present in every slave language
that is enabled for this wiki but Swedish. With such a
configuration, the ikiwiki/wikilink page indeed does not exist
in Swedish language: no ikiwiki/wikilink.sv.po can be found
where ikiwiki is looking. Have a look to
http://l10n.ikiwiki.info/ikiwiki/, the basewiki is not
available in Swedish language on this wiki. So this is not a po
bug, but a configuration or directories layout issue. This is
solved by adding the Swedish basewiki to the underlay dir, which
is I guess not a possibility in the l10n wiki context. I guess
this could be solved by adding SRCDIR/basewiki as an underlay
to your l10n wiki configuration, possibly using the
add_underlays configuration directive. --[[intrigeri]]


There is no complete Swedish underlay translation yet, so it is not
shipped in ikiwiki. I don't think it's a misconfiguration to use
a language that doesn't have translated underlays. --[[Joey]]


Ok. The problem is triggered when using a language that doesn't
have translated underlays, and defining
po_translatable_pages in a way that renders the base wiki
pages translatable in po's view of things, which in turns makes
the po plugin act as if the translation pages did exist,
although they do not in this case. I still need to have a deep
look at the underlays-related code you added to po.pm a while
ago. Stay tuned. --[[intrigeri]]


Fixed in my po branch, along with other related small bugs that
happen in the very same situation only. --[[intrigeri]]