This is a test page for the issue at phab:T258521 and Wikipedia:Village pump (technical)#Interwiki link problem.
Summary: Page names can be at most 255 bytes excluding the namespace. But namespaces are not subtracted from the length in interwiki links so an interwiki link can currently (22 July 2020) be at most 255 bytes including the namespace. This means some valid pages outside mainspace cannot be linked in interwiki links.
Examples edit
All the examples here have exactly 255 a's. This makes a wikilink:
This adds a "b" at the start and fails as it should:
- [[baaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]]
The namespace is excluded in the limit. This works:
An interwiki prefix is also excluded. This works:
But if there is both an interwiki prefix and a namespace then the namespace is included in the limit, also when it's a canonical namespace name like Template and the namespace is called the same in both wikis. This fails:
- [[:simple:Template:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]]
It works if the page name including "Template:" is exactly 255 bytes:
It fails of one more byte is added. This has 247 b's after after "Template:" so the total length is counted as 256:
- [[:simple:Template:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb]]