xitrum-framework/scala-xgettext

.. image:: poedit.png

This is a Scala 2.11, and 2.12 compiler plugin that acts like GNU xgettext command to extract i18n strings in Scala source code files to Gettext <http://en.wikipedia.org/wiki/Gettext>_ .po file, when you compile the Scala source code files.

More info on Scala compiler plugin: http://www.scala-lang.org/node/140

Presentation: I18nize Scala programs à la gettext <http://www.slideshare.net/ngocdaothanh/i18nize-scala-program-a-la-gettext>_

Discussion group: https://groups.google.com/group/scala-xgettext

For Play <https://www.playframework.com/>_: https://github.com/georgeOsdDev/play-xgettext

Usage

This plugin can be used by frameworks like Xitrum <http://xitrum-framework.github.io/> to add i18n feature to them. For an example, see this SBT project <https://github.com/xitrum-framework/comy>.

Create I18n trait or class


In your Scala source code, you need to mark the strings you want to extract by
using a trait or class that has these method signatures:

::

  t(singular: String): String
  tn(singular: String, plural: String, n: Long): String

  tc(context: String, singular: String): String
  tcn(context: String, singular: String, plural: String, n: Long): String

The methods can also be:

::

  t(singular: String, args: Any*): String
  tn(singular: String, plural: String, n: Long, args: Any*): String

  tc(context: String, singular: String, args: Any*): String
  tcn(context: String, singular: String, plural: String, n: Long, args: Any*): String

That is, only the first arguments (1 first argument for ``t``, 3 first arguments
for ``tn`` etc.) are required, all the following arguments are ignored
(like `params` above).

You can use `Scaposer <https://github.com/xitrum-framework/scaposer>`_ to
implement the methods above. See `example <https://github.com/xitrum-framework/xitrum/blob/master/src/main/scala/xitrum/I18n.scala>`_.

Then in your Scala source code, use them like this:

::

  t("Hello World")
  t("Hello %s").format("World")

  t("%,.3f").format(1234.5678)                                // => 1,234.568
  t("%,.3f").formatLocal(java.util.Locale.FRANCE, 1234.5678)  // => 1 234,568

If you have more than one placeholder:

::

  // 1$ and 2$ are placeholders
  t("%1$s says hello to %2$s, then %2$s says hello back to %1$s").format("Bill", "Hillary")

  // {0} and {1} are placeholders
  java.text.MessageFormat.format(t("{0} says hello to {1}, then {1} says hello back to {0}"), "Bill", "Hillary")

**Important: The arguments ``singular``, ``plural``, and ``context`` MUST be literal constant string, like in the above
examples. Otherwise exception will be thrown during compilation. Alternatively, one can add the option
``ignoreNonLiteralStrings:true`` to ignore those cases instead of throwing an exception**

Extract i18n strings to .pot file

To extract i18n strings like "Hello World" in the above snippet:

Clean your Scala project to force the recompilation of all Scala source code files.
Create an empty i18n.pot file in the current working directory. It will be filled with i18n string resources extracted from compiled Scala source code files.
Compile your Scala project with -P:xgettext:<i18n trait or class> option. Example: -P:xgettext:xitrum.I18n.

If you use SBT <http://www.scala-sbt.org/>_, build.sbt should look like this:

... autoCompilerPlugins := true addCompilerPlugin("tv.cntt" %% "xgettext" % "1.5.1") scalacOptions += "-P:xgettext:xitrum.I18n" ...

Copy or rename the .pot file to a .po file, and translate the strings in it to the language if want. "t" in ".pot" means "template".

You can use plain text editor to edit the .po file, or you can use Poedit <http://poedit.net/>_. Poedit is very convenient, it can merge new .pot file to existing translated .po file.

Content of the .pot file is sorted by msgid, so that it's easier too see diffs between versions of the .pot/.po file.

Configure i18n marker method names


``t``, ``tn``, ``tc``, and ``tcn`` above are the defaults.

If you want to use other names, you can change them to, for example,
``tr``, ``trn``, ``trc``, and ``trcn``, by adding options to Scala compiler:

::

  scalacOptions ++= Seq(
    "xitrum.I18n", "t:tr", "tn:trn", "tc:trc", "tcn:trcn"
  ).map("-P:xgettext:" + _)

If you skip an option, its default value will be used.

Multiple marker method names

Multiple marker methods for t can be configured like this:

scalacOptions ++= Seq( "xitrum.I18n", "t:tr", "t:notr" ).map("-P:xgettext:" + _)

Similar for tn, tc, and tcn.

With this feature you can, for example, create an i18n library that can display both original strings and translated strings.

Explicitly specifying the plural forms for the template


Some translation software require the plural forms formula used in the template
to be explicitly stated.

::

  scalacOptions ++= "-P:xgettext:sourceLang:en"

Or:

::

  scalacOptions ++= "-P:xgettext:rawPluralForm:<nplurals=#; formula>"

Using one of these options will cause the template to have a Plural-Forms header.
Many languages are supported, but see ``src/main/scala/scala/PluralForms.scala``
for all of the languages supported and examples of the common formulas.

Omitting this option will omit a Plural-Forms header from the template output.

Load .po file

Use Scaposer <https://github.com/xitrum-framework/scaposer>_.

xitrum-framework / scala-xgettext

readme

Usage