i18nize Scala programsà la gettext

Episode 39, Wed, Aug 12, 2015Ngoc Dao

About the speaker

● Ngoc Dao● Joined Atlassian since May

● Favorite languages:Ruby, Erlang, Scala

● Favorite languages:Ruby, Erlang, Scala

● My Scala style:Using Scala as ifScala = Java (performance, libs eco) + Ruby (human oriented) + Erlang (functional)

● Don’t know Scalaz/Haskell (yet)

↑↑↑

Struggling withmonadic talks at ScalaSyd

English is not my native language● From Viet Nam● 15 years in Japan

↑↑↑

i18n is important to me

Given this program:printf("My name is %s.", myName)

Given this program:printf("My name is %s.", myName)

Let’s i18nize it in gettext style!

(I won’t go into details of .properties style vs gettext style)

(1) Mark the strings we want to translate

printf(t("My name is %s."), myName)

i18n.pot template file:

msgid "My name is %s."

msgstr ""

(2) Extract to a template file

(1) Mark the strings we want to translate

printf(t("My name is %s."), myName)

i18n.pot template file:

msgid "My name is %s."

msgstr ""

fr.po language file:

msgid "My name is %s."

msgstr "Je m'appelle %s."

(2) Extract to a template file

(3) Give it to translators

(1) Mark the strings we want to translate

printf(t("My name is %s."), myName)

When strings in the program change, how to update (add, remove, modify) language files efficiently?

When strings in the program change, how to update (add, remove, modify) language files efficiently?● Automatically copy similar existing

translation to make new translation (marked as “fuzzy” to be modified by a human later)

When strings in the program change, how to update (add, remove, modify) language files efficiently?● Automatically copy similar existing

translation to make new translation (marked as “fuzzy” to be modified by a human later)

● Don’t delete, just comment out dated translations for future references

When strings in the program change, how to update (add, remove, modify) language files efficiently?● Automatically copy similar existing

translation to make new translation (marked as “fuzzy” to be modified by a human later)

● Don’t delete, just comment out dated translations for future references

● In translation files, sort by msgid so that it’s easier to diff versions

fr.po language file:

msgid "My name is %s."

msgstr "Je m'appelle %s."

ja.po language file:

msgid "My name is %s."

msgstr "%sと申します。 "

(4) Load language files to program,basically parse the files tokey → valuedata structure

vi.po language file:

msgid "My name is %s."

msgstr "Tôi tên là %s."

printf(t("My name is %s."), myName)

printf("Je m’appelle %s.", myName)

(5) At run time, the marker acts as a function to replace the given key with its value

gettext is quite advanced

● Allow specifying context(one string may be translated to different strings, depending on context)

print(t("Hello"))print(tc("Casual", "Hello"))

fr.po language file:

msgid "Hello"msgstr "Bonjour"

msgctxt "Casual"msgid "Hello"

msgstr "Salut"

gettext is quite advanced

● Allow specifying singular/plural rules(different languages may have different singular/plural rules)

print(tn( "I have one apple", "I have %d apples", numApples))

Singular

Plural

Depending on this value

fr.po language file:

msgid ""msgstr "Plural-Forms: nplurals=2; plural=n>1;"

msgid "I have one apple"msgid_plural "I have %d apples"msgstr[0] "J'ai une pomme"msgstr[1] "J'ai %d pommes"

Singular/plural ruleSpecial key

DemoI’ll introduce some tools

Hello.scala

println("Hello world")

Mark and extract i18n strings

Mark and extract i18n strings

Tool:https://github.com/xitrum-framework/scala-xgettext

It’s a Scala compiler plugin, to extract i18n strings at compile time.

Mark and extract i18n strings

Tool:https://github.com/xitrum-framework/scala-xgettext

It’s a Scala compiler plugin, to extract i18n strings at compile time.

↑↑↑Neat! Just compile Scala source code and get the strings.

Scala is powerful

● scala-xgettext can also extracts i18n strings from view templates

● as long as the templates are converted to Scala source code and compiled

Mark and extract i18n strings

● scala-xgettext can also extracts i18n strings from view templates

● as long as the templates are converted to Scala source code and compiled

↑↑↑It works for all popular Scala template engines like Scalate, Scalatags, Twirl (Play framework template engine)

Mark and extract i18n strings

Translate language template file

Translate language template file

Tool:Any text editor

Translate language template file

Tool:Any text editor

Very convenient GUI editor:

https://poedit.net/

Load language file

Tool:https://github.com/xitrum-framework/scaposer

It’s a Scala parser to transform .po text file intokey → valuedata structure

Poedit demo: Update i18n strings

● Add, modify, remove i18n strings in program● Regenerate i18n.pot file● Use Poedit to update existing .po files with

the new i18n.pot file● Poedit can give translation hints for similar

strings

Demo source code:https://github.com/xitrum-framework/scala-xgettext-presentation

If you use Play framework:https://github.com/georgeOsdDev/play-xgettext