TYPO3 Core

Following languages key for config.yaml

  -
    title: Deutsch
    enabled: true
    languageId: 0
    base: /
    typo3Language: de
    locale: de_DE.UTF-8
    iso-639-1: de
    navigationTitle: Deutsch
    hreflang: de-DE
    direction: ''
    flag: de
    websiteTitle: ''
    solr_core_read: core_de
  -
    title: English
    enabled: true
    base: /en/
    typo3Language: default
    locale: en_US.UTF-8
    iso-639-1: en
    websiteTitle: ''
    navigationTitle: ''
    hreflang: ''
    direction: ''
    fallbackType: fallback
    fallbacks: '0'
    flag: en-us-gb
    languageId: 1
    solr_core_read: core_en

In the confguration you see the problem, the hreflang field is empty for english language, so no hreflang tags are generated because only 1 language in with a hreflang field.

The problem behind this is, the missing hreflang entry is shown with a correctly filled placeholder value 'en-US' in the backend of the site configuration. So the configuration error is very hard to spot using only the typo3 backend.

My expectation would be, that if there is a placeholder value, this placeholder value would be used if the field is empty.

What i dont know is if this behaviour still exists on the current version.