How to set source language for @angular/localize

After you’ve installed @angular/localize, you can set the source language in angular.json: Add

"i18n": {
  "sourceLocale": "de",
},

to your project, for example:

[...]
"projects": {
  "MyApplication": {
    "projectType": "application",
    "schematics": {
      "@schematics/angular:component": {
        "style": "sass"
      }
    },
    "i18n": {
      "sourceLocale": "de",
      "locales": {
        "en": "src/locale/messages.en.xlf"
      }
    },
    "root": "",
    "sourceRoot": "src",
    "prefix": "app",
    "architect": {
[...]