If I add a default keywords string to the metas settings, say in src/_data.yml like this:
...
metas:
lang: en
...
default_keywords: [aaaaa,bbbbb,ccccc]
keywords: "=tags || =default_keywords"
......then I get what you can see in 2. example source.html, metas plugin just adds them as arbitrary meta tags. Conversely the actual keywords meta is not populated, for a page without any tags set.
If I add a default keywords string outside the metas settings in src/_data.yml like this:
...
default_keywords: [aaaaa,bbbbb,ccccc]
metas:
lang: en
...
keywords: "=tags || =default_keywords"
......nothing happens. The actual keywords meta is not added, for a page without any tags set, nor are any meta tags added.
Similarly, if I add the defaults into src/en/pages/_data.yml, where the page lives, like this
lang: en
default_keywords: [aaaaa,bbbbb,ccccc]
templateEngine:
- vto
- md
...nothing happens, and you don't see these in the source of the page with no tags set, in any way.