In an extension with template event files that use language vars, the language vars are injected with a newline immediately after each lang var.
Example: an extension template file (i.e.: overall_footer_after.html) contains:
This is rendered by phpBB in HTML as:
Note the new line added after the language var! This happens for both LA_ and L_ language vars anywhere they may be used in extension template files. It also does not matter if the extension's template is using core phpBB lang vars, and/or its own. It happens in all cases with extension templates.
Update: This isn't limited to language vars. It's any where a curly brace variable is used in an event template file, i.e.:
Notice that every } closing curly brace creates a newline in the html output
I also examined a cached file, to see how the php is being rendered by the template engine, and found the previous example to look something like this:
As you can see, actually two newlines are added between the closing php tag and the double quote from the template!
So it is like the template engine is adding ?>\n\n for every closing curly brace.