Name¶
Dist::Zilla::LocaleTextDomain - Tools for managing Locale::TextDomain language
catalogs
Synopsis¶
In
dist.ini:
[ShareDir]
[LocaleTextDomain]
textdomain = My-App
share_dir = share
Scan localizable messages from your Perl libraries into a language template
file,
po/My-App.pot:
dzil msg-scan
Initialize language translation files:
dzil msg-init fr de.UTF-8
Merge changes to localizable messages into existing translation files:
dzil msg-merge
Compile translation files into message catalogs for testing:
dzil msg-compile --dest-dir . fr de.UTF-8
Binary message catalogs are automatically added to your distribution by the
"build" and "release" commands:
dzil build
dzil release
Description¶
Locale::TextDomain provides a nice interface for localizing your Perl
applications. The tools for managing translations, however, is a bit arcane.
Fortunately, you can just use this plugin and get all the tools you need to
scan your Perl libraries for localizable strings, create a language template,
and initialize translation files and keep them up-to-date. All this is
assuming that your system has the gettext
<
http://www.gnu.org/software/gettext/> utilities installed.
The Details¶
I put off learning how to use Locale::TextDomain for quite a while because,
while the gettext <
http://www.gnu.org/software/gettext/> tools are great
for translators, the tools for developers were a little more opaque,
especially for Perlers used to Locale::Maketext. But I put in the effort while
hacking Sqitch. As I had hoped, using it in my code was easy. Using it for my
distribution was harder, so I decided to write Dist::Zilla::LocaleTextDomain
to make life simpler for developers who manage their distributions with
Dist::Zilla.
What follows is a quick tutorial on using Locale::TextDomain and managing its
translation files with Dist::Zilla::LocaleTextDomain.
This is my domain¶
First thing to do is to start using Locale::TextDomain in your code. Load it
into each module with the name of your distribution, as set by the
"name" attribute in your
dist.ini file. For example, if your
dist.ini looks something like this:
name = My-GreatApp
author = Homer Simpson <homer@example.com>
license = Perl_5
Then, in you Perl libraries, load Locale::TextDomain like this:
use Locale::TextDomain qw(My-GreatApp);
use Locale::Messages qw(bind_textdomain_filter);
use Encode;
$ENV{OUTPUT_CHARSET} = 'UTF-8';
bind_textdomain_filter 'My-GreatApp' => \&Encode::decode_utf8;
Locale::TextDomain uses the string we pass to it to find localization catalogs,
so naturally Dist::Zilla::LocaleTextDomain will use it to put those catalogs
in the right place. It's also a best practice to coerce Locale::TextDomain to
return character strings, rather than bytes, by setting the $OUTPUT_CHARSET
environment variable to "UTF-8" and then binding a filter to decode
the resulting strings into Perl character strings. This makes it easier to
work with such strings in our application. Just be sure to encode them before
outputting them!
Okay, so it's loaded, how do you use it? The documentation for the
Locale::TextDomain exported functions is quite comprehensive, and I think
you'll find it pretty simple once you get used to it. For example, simple
strings are denoted with "__":
say __ 'Hello';
If you need to specify variables, use "__x":
say __x(
'You selected the color {color}',
color => $color
);
Need to deal with plurals? Use "__n"
say __n(
'One file has been deleted',
'All files have been deleted',
$num_files,
);
And then you can mix variables with plurals with "__nx":
say __nx(
'One file has been deleted.',
'{count} files have been deleted.',
$num_files,
count => $num_files,
);
Pretty simple, right? Get to know these functions, and just make it a habit to
use them in user-visible messages in your code. Even if you never expect to
translate those messages, just by doing this you make it easier for someone
else to come along and start translating for you.
The setup¶
Now you've internationalized your code. Great! What's next? Officially, nothing.
If you never do anything else, your code will always emit the messages as
written. You can ship it and things will work just as if you had never done
any localization.
But what's the fun in that? Let's set things up so that translation catalogs
will be built and distributed once they're written. Add these lines to your
dist.ini:
[ShareDir]
[LocaleTextDomain]
There are actually quite a few attributes you can set here to tell the plugin
where to find language files and where to put them. For example, if you used a
domain different from your distribution name, e.g.,
use Locale::TextDomain 'com.example.My-GreatApp';
Then you would need to set the "textdomain" attribute so that the
"LocaleTextDomain" plugin does the right thing with the language
files:
[LocaleTextDomain]
textdomain = com.example.My-GreatApp
Consult the "LocaleTextDomain" configuration docs for details on all
available attributes.
(Prior to Locale::TextDomain v1.21, there was no
"ShareDir" support. If you're unfortunate to
be stuck with one of these earlier versions, you'll need to set the
"share_dir" attribute to
"lib" instead of the default value,
"share" . If you use Module::Build, you'll also
need a subclass to do the right thing with the catalog files; see
"Installation" in Dist::Zilla::Plugin::LocaleTextDomain for
details.)
What does including the plugin do? Mostly nothing. You might see this line from
"dzil build", though:
[LocaleTextDomain] Skipping language compilation: directory po does not exist
Now at least you know it was looking for something to compile for distribution.
Let's give it something to find.
Initialize languages¶
To add translation files, use the "msg-init" command:
> dzil msg-init de
Created po/de.po.
At this point, the gettext <
http://www.gnu.org/software/gettext/>
utilities will need to be installed and visible in your path, or else you'll
get errors.
This command scans all of the Perl modules gathered by Dist::Zilla and
initializes a German translation file, named
po/de.po. This file is now
ready for your German-speaking public to start translating. Check it into your
source code repository so they can find it. Create as many language files as
you like:
> dzil msg-init fr ja.JIS en_US.UTF-8
Created po/fr.po.
Created po/ja.po.
Created po/en_US.po.
As you can see, each language results in the generation of the appropriate file
in the
po directory, sans encoding (i.e., no
.UTF-8 in the
"en_US" file name).
Now let your translators go wild with all the languages they speak, as well as
the regional dialects. (Don't forget to colour your code with
"en_UK" translations!)
Once you have translations and they're committed to your repository, when you
build your distribution, the language files will automatically be compiled
into binary catalogs. You'll see this line output from "dzil build":
[LocaleTextDomain] Compiling language files in po
po/fr.po: 10 translated messages, 1 fuzzy translation, 0 untranslated messages.
po/ja.po: 10 translated messages, 1 fuzzy translation, 0 untranslated messages.
po/en_US.po: 10 translated messages, 1 fuzzy translation, 0 untranslated messages.
You'll then find the catalogs in the shared directory of your distribution:
> find My-GreatApp-0.01/share -type f
My-GreatApp-0.01/share/LocaleData/de/LC_MESSAGES/My-GreatApp.mo
My-GreatApp-0.01/share/LocaleData/en_US/LC_MESSAGES/My-GreatApp.mo
My-GreatApp-0.01/share/LocaleData/ja/LC_MESSAGES/My-GreatApp.mo
These binary catalogs will be installed as part of the distribution just where
"Locale::TextDomain" can find them.
Here's an optional tweak: add this line to your "MANIFEST.SKIP":
^po/
This prevents the
po directory and its contents from being included in
the distribution. Sure, you can include them if you like, but they're not
required for the running of your app; the generated binary catalog files are
all you need. Might as well leave out the translation files.
But I'm a Translator¶
Not a developer, but want to translate a project? I've written this special
section just for you.
Translating your language is relatively straight-forward. First, make sure that
the translation file is up-to-date. Say you're translating into French; use
the "msg-merge" command to update the translation file:
> dzil msg-merge po/fr.po
[LocaleTextDomain] Merging gettext strings into po/fr.po
If you get an error about it not existing, use the "msg-init" command
to create it:
> dzil msg-init fr
[LocaleTextDomain] Created po/fr.po.
Now edit
po/fr.po. You can use a tool such as Poedit
<
http://www.poedit.net> or Emacs
<
https://www.gnu.org/software/gettext/manual/html_node/PO-Mode.html> to
make it easier. As you work, you can use the "msg-compile" command
to make sure that you're translation file is error-free:
> dzil msg-compile po/fr.po
[LocaleTextDomain] po/fr.po: 195 translated messages.
This command compiles a catalog file into the
LocaleData subdirectory of
the current directory (or directory of your choice via the
"--dest-dir" option), so that you can even run the app with the
compiled catalog to make sure things look the way you think they ought to.
Just set the $LANGUAGE environment variable and make sure that Perl includes
the current directory in its path, something like:
LANGUAGE=fr perl -I . bin/myapp.pl
Consult the developer for help with this bit, as how apps run varies between
projects.
Mergers and acquisitions¶
You've got translation files and helpful translators given them a workover. What
happens when you change your code, add new messages, or modify existing ones?
The translation files need to periodically be updated with those changes, so
that your translators can deal with them. We got you covered with the
"msg-merge" command:
> dzil msg-merge
extracting gettext strings
Merging gettext strings into po/de.po
Merging gettext strings into po/en_US.po
Merging gettext strings into po/ja.po
This will scan your module files again and update all of the translation files
with any changes. Old messages will be commented-out and new ones added. Just
commit the changes to your repository and notify the translation army that
they've got more work to do.
If for some reason you need to update only a subset of language files, you can
simply list them on the command-line:
> dzil msg-merge po/de.po po/en_US.po
Merging gettext strings into po/de.po
Merging gettext strings into po/en_US.po
What's the scan, man¶
Both the "msg-init" and "msg-merge" commands depend on a
translation template file to create and merge language files. Thus far, this
has been invisible: they will create a temporary template file to do their
work, and then delete it when they're done.
However, it's common to also store the template file in your repository and to
manage it directly, rather than implicitly. If you'd like to do this, the
"msg-scan" command will scan the Perl module files gathered by
Dist::Zilla and make it for you:
> dzil msg-scan
extracting gettext strings into po/My-GreatApp.pot
The resulting
.pot file will then be used by "msg-init" and
"msg-merge" rather than scanning your code all over again. This
actually then makes "msg-merge" a two-step process: You need to
update the template before merging. Updating the template is done by exactly
the same command, "msg-scan":
> dzil msg-scan
extracting gettext strings into po/My-GreatApp.pot
> dzil msg-merge
Merging gettext strings into po/de.po
Merging gettext strings into po/en_US.po
Merging gettext strings into po/ja.po
Ship It!¶
And that's all there is to it. Go forth and localize and internationalize your
Perl apps!
Author¶
David E. Wheeler <david@justatheory.com>
Copyright and License¶
This software is copyright (c) 2012-2013 by David E. Wheeler.
This is free software; you can redistribute it and/or modify it under the same
terms as the Perl 5 programming language system itself.