Check translations from [.properties](https://en.wikipedia.org/wiki/.properties) files with [Mustache](http://mustache.github.io/) placeholders markup or [messageformat](https://messageformat.github.io/messageformat/) syntax.

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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 {
} = 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':
          case 'empty-message':
            // less severe, lets log it with WARN severity instead of ERROR
          default:  // 'wrong-messageformat', 'wrong-placeholder'
            // This are more severe errors
    } 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.

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')
- empty-message - empty message found in a translation

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).


$ npm publish --access=public