I created this version using wikitext editing, and it had <syntaxhighlight inline lang="perl">use strict;</syntaxhighlight>. Note the inline attribute without any parameter.
Then I edited the page using VE. I only changed the content of the tag. When I saved, inline changed to inline="". Is that correct?
The final rendering is the same, but what is the right way to store the attribute code? The documentation at Extension:SyntaxHighlight has no parameter at all.
The PHP code only checks to see if an "inline" attribute has been provided in the tag definition. No check is done to see if there is an associated value or not. It is relatively common to see HTML linters that get confused about bare attributes like "selected" and "checked" to recommend `attribute="attribute"` usage. There is nothing technical wrong with VE using `attribute=""` in this similar situation.
It does sound like behavior that could be considered a dirty diff from parsoid round tripping.
In HTML, omitting the attribute value means exactly the same as setting it to the empty string. The legacy parser also treats them same when parsing extension tags (so there is no right way, both are equal and thus equally right); I suppose this is true for Parsoid as well.
(By the way, the comment in Sanitizer.php also notes that omitting the tag value is invalid in XHTML, so probably the linters that get confused are XHTML/XML linters, not real HTML linters.)