translation-checker

Check translations from .properties files with Mustache placeholders markup or messageformat syntax.

Getting started

Node 8.10+ required. Install with:

$ npm install @medic/translation-checker

Here is how you can use it:

const {
  checkTranslations,
  TranslationException
} = require('@medic/translation-checker');

const dir = `${somePath}/translations`;
let fileNames;
try {
  fileNames = await checkTranslations(dir);
  // Your files passed the validations!
  // fileNames = ['messages-en.properties', 'messages-es.properties', ...]
} catch (err) {
    if (err instanceof TranslationException) {
      // Oops, translation errors !!
      fileNames = err.fileNames;  // ['messages-en.properties', 'messages-es.properties', ...]
      if (!err.errors) {
        return log.error('Exception checking translations:', err.message);
      }
      for (const error of err.errors) {
        switch (error.error) {
          case 'cannot-access-dir':
            return log.warn('Could not find custom translations dir:', dir);
          case 'missed-placeholder':
          case 'wrong-placeholder':
            log.error(error.message);
            break;
          case 'missing-key':
          case 'empty-message':
            // less severe, lets log it with WARN severity instead of ERROR
            log.warn(error.message);
            break;
          default:  // 'wrong-messageformat', 'wrong-placeholder'
            // This are more severe errors
            log.error(error.message);
            break;
        }
      }
    } else {
      throw err;  // unexpected ;(
    }
}

Logs from the example above will look like:

WARN Empty message found for key 'report.pregnancy.u_lmp_date' in 'en' translation 
WARN Empty message found for key 'report.pregnancy.method_lmp' in 'en' translation 
ERROR Cannot compile 'es' translation with key 'Number in month' has placeholders that do not match any in the base translation provided 
ERROR Cannot compile 'es' translation n.month = '{MONTHS, plural one{1 mes} other{# meses}}' : Expected "," but "o" found.

Arguments

checkTranslations(dir, options) (async)

dir: the directory to scan
options.languages: Array of lowercase ISO 639-1 code languages to be checked. Defaults to all valid files found in dir.
options.checkPlaceholders: Whether to check missed placeholders or not. Defaults to true.
options.checkMessageformat: Whether to check wrong Messageformat or not. Defaults to true.
options.checkEmpties: Whether to check empty messages or not. Defaults to true.
options.checkMissing: Whether to ensure all keys in "en" file also exist in other languages. Defaults to false.

Error details

All the errors raised by checkTranslations() are instances of TranslationException. The exception object has an errors array with one object for each error detected as following:

{
  "lang": "en",                     // The language where the error was found
  "error": "wrong-messageformat",   // The error code
  "key": "n.month2",                // The translation key
  "message": "Cannot compile ..."   // A message with more details about the error
}

These are the error codes and what they mean:

cannot-access-dir - the directory passed doesn't exist or is not accessible
wrong-file-name - one of the translation files has a wrong name or has an unknown ISO 639 language code on it, eg. messages-e$.properties
missed-placeholder - a mustache placeholder eg. {{firstName}} was found in a translation, but main translations ('en' or 'ex') don't have placeholders for that translation at all
wrong-placeholder - a mustache placeholder eg. {{firstName}} was found in a translation that do not match any in the base translations ('en' or 'ex') placeholders
empty-message - empty message found in a translation
missing-key - a key was found in the English translation file but not found in one of the other languages

Placeholders check

The mustache placeholder check works as following:

You need to call checkTranslations(dir, options) with options.checkPlaceholders = true (default).
options.languages needs to be unset (default) or set at least with one or both of the two codes considered "template" languages: 'en', 'ex'
'ex' is not a real ISO language code, but if you have a messages-ex.properties file, you can place there placeholders that can be used for a specific key, eg. hello = {{firstName}} {{lastName}} {{username}}
'en' language (messages-en.properties) is considered the "template" or base language, and any placeholder used in any other translation file other than 'en' or 'ex' needs to be present in one of these two templates. Eg. if you have in the 'en' translation the following translation records.total = {{count}} records, this is a valid 'es' translation: records.total = {{count}} registros but this not: records.total = {{count}} registros de {{max}}. You can use the {{max}} placeholder either adding it to the 'en' translation or adding an entry in the messages-ex.properties file like this: records.total = {{max}} (or records.total = {{count}} {{max}})

Check the JSDoc of the source code to see more options.

Messageformat check

"Messageformat" check are also performed by default, you can disable it with options.checkMessageformat = false.

A common error is by mistake translate the messageformat keywords when using online translator tools, eg. this translation that is OK in English:

n.month = {MONTHS, plural, one{1 month} other{\# months}}

Wrong translated to Spanish:

n.month = {MONTHS, plural, uno{1 mes} otros{\# meses}}

Will raise an error with a the message:

Invalid key `uno` for argument `MONTHS`. Valid plural keys for this locale are `one`,
`other`, and explicit keys like `=0`

The right translations is:

n.month = {MONTHS, plural, one{1 mes} other{\# meses}}

Empty message checks

Validations fail if a key is found like this:

n.month =

But some times empty keys are acceptable because the software that use the translations fallback to the default language, so to disable empties check set options.checkEmpties to false (default is true).

Publishing

$ npm publish --access=public