As a user, I want to enter pagenames/filenames without triggering a constraint violation because of (missing) underscores.
**Problem:**
Currently, Wikibase does not normalize pagenames/filenames on save (e.g. underscores in the input for properties of datatype Commons media are allowed).
At the same time, Wikidata’s [[ https://www.mediawiki.org/wiki/Extension:WikibaseQualityConstraints | quality constraints extension ]] triggers a constraint violation after saving, if underscores are used. This is by design as to [[ https://www.wikidata.org/wiki/Template:Constraint:Commons_link | long-established ]] Community practices.
As a result, this inconsistency leaves users with unnecessary manual work.
**Example:**
Currently, we don't normalize the file name ("_" not removed on save)
* https://test.wikidata.org/w/index.php?title=Q212413&diff=prev&oldid=529671
We do already normalize sitelinks ("_" removed on save)
* https://test.wikidata.org/w/index.php?title=Q212413&diff=next&oldid=529671 (edit included an underscore)
**Acceptance criteria:**
* for new edits, if the pagenames/filenames is changed, pagenames/filenames are normalized on save ("my file_name.jpg" -> "my file name.jpg")
**Open questions:**
* Standard Mediawiki-normalization for pagenames/filenames in Wikidata uses the opposite normalization ("file_name.jpg" -> "file_name.jpg"). How much of a problem is this inconsistency?
**Original:**
misleading: "Commons link should be well-formed." warning
If an image name (e.g. P18, P1442) does contain underscores '_', wikidata considers this to be ill-formed. Now
* Grab fritz jellinek wiener zentralfriedhof 2020-01-30(2).jpg and
* Grab_fritz_jellinek_wiener_zentralfriedhof_2020-01-30(2).jpg are identical by definition and the warning is an annoyance
So please can you silently do all the necessary underscore <-> space replacements by the underlying software instead of propagating it to the users.