Do you want this for the Special:EntityData code in Wikibase to reply with a 303 See Other to the JSON format if RDF isn't supported? Do you want a task for "support export in RDF in WBMI" too?

A 303 answer looks like a good option indeed.

Do you want a task for "support export in RDF in WBMI" too?

I just created one: T215341

Just noticed this is still happening in 1.33.0-wmf.17.

More info if helpful (even if not ):

id: XGSZqQpAMFQAACoNLsEAAACC

message: PHP Fatal Error: Argument 1 passed to Wikibase\Rdf\RdfBuilder::addEntityRedirect() must be an instance of Wikibase\DataModel\Entity\EntityId, null given

Trace:

#0 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/LinkedData/EntityDataSerializationService.php(261): NO_FUNCTION_GIVEN()
#1 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/LinkedData/EntityDataSerializationService.php(237): Wikibase\Repo\LinkedData\EntityDataSerializationService->addIncomingRedirects(Wikibase\MediaInfo\DataModel\MediaInfoId, NULL, array, Wikibase\Rdf\RdfBuilder)
#2 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/LinkedData/EntityDataSerializationService.php(175): Wikibase\Repo\LinkedData\EntityDataSerializationService->rdfSerialize(Wikibase\Lib\Store\EntityRevision, NULL, array, Wikibase\Rdf\RdfBuilder, NULL)
#3 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/LinkedData/EntityDataRequestHandler.php(503): Wikibase\Repo\LinkedData\EntityDataSerializationService->getSerializedData(string, Wikibase\Lib\Store\EntityRevision, NULL, array, NULL)
#4 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/LinkedData/EntityDataRequestHandler.php(254): Wikibase\Repo\LinkedData\EntityDataRequestHandler->showData(WebRequest, OutputPage, string, Wikibase\MediaInfo\DataModel\MediaInfoId, integer)
#5 /srv/mediawiki/php-1.33.0-wmf.17/extensions/Wikibase/repo/includes/Specials/SpecialEntityData.php(154): Wikibase\Repo\LinkedData\EntityDataRequestHandler->handleRequest(string, WebRequest, OutputPage)
#6 /srv/mediawiki/php-1.33.0-wmf.17/includes/specialpage/SpecialPage.php(569): Wikibase\Repo\Specials\SpecialEntityData->execute(string)
#7 /srv/mediawiki/php-1.33.0-wmf.17/includes/specialpage/SpecialPageFactory.php(558): SpecialPage->run(string)
#8 /srv/mediawiki/php-1.33.0-wmf.17/includes/MediaWiki.php(288): MediaWiki\Special\SpecialPageFactory->executePath(Title, RequestContext)
#9 /srv/mediawiki/php-1.33.0-wmf.17/includes/MediaWiki.php(867): MediaWiki->performRequest()
#10 /srv/mediawiki/php-1.33.0-wmf.17/includes/MediaWiki.php(517): MediaWiki->main()
#11 /srv/mediawiki/php-1.33.0-wmf.17/index.php(42): MediaWiki->run()
#12 /srv/mediawiki/w/index.php(3): include(string)
#13 {main}

Change 490581 had a related patch set uploaded (by WMDE-leszek; owner: WMDE-leszek):
[mediawiki/extensions/Wikibase@master] Added a setting to specify entity types for which RDF output is not available.

https://gerrit.wikimedia.org/r/490581

Change 490587 had a related patch set uploaded (by WMDE-leszek; owner: WMDE-leszek):
[operations/mediawiki-config@master] Disable RDF output of mediainfo Wikibase entities

https://gerrit.wikimedia.org/r/490587

Change 490586 had a related patch set uploaded (by WMDE-leszek; owner: WMDE-leszek):
[operations/mediawiki-config@master] Added a setting to define Wikibase entity types that have no RDF output

https://gerrit.wikimedia.org/r/490586

Some other example:

The 16 exceptions logged were using different file extensions:

https://www.wikidata.org/wiki/Special:EntityData/M22857511.n3
https://www.wikidata.org/wiki/Special:EntityData/M22857511.rdf
https://www.wikidata.org/wiki/Special:EntityData/M22857511.ttl
https://www.wikidata.org/wiki/Special:EntityData/M22857511.nt

M22857511 is File:Glühwendel brennt durch.jpg, which has a redirect from File:Glühwedel brennt durch.jpg (missing ‘n’ in “-wendel”). Does this only affect files with incoming redirects?

No, RDF is not working for MediaInfo in general, and hence we (WMDE) suggested to disable it until the RDF mapping is done, and Structured Data on Commons team decides to enable RDF output back.

Change 490581 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Added a setting to specify entity types for which RDF output is not available.

https://gerrit.wikimedia.org/r/490581

So, next step is to configure entityTypesWithoutRdfOutput to [ 'mediainfo' ]?

@Jdforrester-WMF yup.
Those config changes would be rather straightforward, and I am sure you'd be able to cook them yourselves. I've drafted https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/490586 and https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/490587 a while back. I wouldn't object if those were SWAT'ed. If helpful WMDE would try to help with deployment these (verification etc), although as you already know, we're generally only available in those crazy European times

Change 490586 merged by jenkins-bot:
[operations/mediawiki-config@master] Added a setting to define Wikibase entity types that have no RDF output

https://gerrit.wikimedia.org/r/490586

Mentioned in SAL (#wikimedia-operations) [2019-03-21T19:39:22Z] <jforrester@deploy1001> Synchronized wmf-config/InitialiseSettings.php: T213483 Set default wmgWikibaseEntityTypesWithoutRdfOutput value (duration: 00m 51s)

Mentioned in SAL (#wikimedia-operations) [2019-03-21T19:40:45Z] <jforrester@deploy1001> Synchronized wmf-config/Wikibase.php: T213483 Read wmgWikibaseEntityTypesWithoutRdfOutput value (duration: 00m 50s)

Change 490587 merged by jenkins-bot:
[operations/mediawiki-config@master] Disable RDF output of mediainfo Wikibase entities

https://gerrit.wikimedia.org/r/490587

Mentioned in SAL (#wikimedia-operations) [2019-03-21T19:45:55Z] <jforrester@deploy1001> Synchronized wmf-config/Wikibase.php: T213483 Disable RDF output of mediainfo Wikibase entities (duration: 00m 49s)

There’s a train blocker that I think may be caused by the fix to this issue, please see T218950.