I am currently in the process of adding en locale to an Angular App we are using at my company. After some thinking we decided to go with the Angular 5+ native i18n support.
From how I understand it however, everytime the translation file is generated with ng xi18n --outputPath src/locale/ --locale en a new file is created. This means, that every time a new i18n tag is added, the previous XLF file which already contains the old translations, needs to be merged with the new translations.
This seems highly bothersome, therefore my question: Is there a way such that the new trans-units are just appended to the already existing XLF file? Or is there already a tool which can merge these two together?
EDIT: xliffmerge seems to be unmaintained and incompatible with latest Angular versions (> 12). See answer by @daniel-sc for an option for latest Angular versions.
Edited answer
You can use the xliffmerge tool. It can merge translation files after you've added new translations in your html
Here is a tutorial for angular
Basically after running your normal extract command you call xliffmerge and pass the language(s) for which you want to generate translation files
ng xi18n --outputPath src/locale/ --locale en && xliffmerge --profile xliffmerge.json en fr
You can specify a json config for the tool
{
"xliffmergeOptions": {
"srcDir": "src/locale",
"genDir": "src/locale"
}
}
Original answer
Try setting custom ids to your translations
https://angular.io/guide/i18n#set-a-custom-id-for-persistence-and-maintenance
<h1 i18n="@@introductionHeader">Hello i18n!</h1>
Nex time you run the extract command, it'll just add the new blocks but won't touch the existing ones
Btw I think going with the native option is a good choice, since the maintainer of the main alternative (ngx-translate) is actually working with the angular team on the native approach