Using roaster requires a seemingly unused `output` prefix to be declared in the consuming code

[DrRataplan]

See https://github.com/eeditiones/roaster/blob/main/test/app/modules/api.xql#L4. The output prefix is not actually used. But removing it gives a dynamic error from Roaster:

 <?xml version="1.0" ?><exception><path>/db/apps/betmas-id-manager/modules/api.xql</path><message>err:XPST0081 No namespace defined for prefix output:method [at line 449, column 5, source: /db/system/repo/roaster-1.12.1/content/router.xql]

Can we circumvent this in some way? Maybe by using fn:QName in router.xql? I don't really like dead imports. It encourages cargo culting and makes one afraid to remove unused namespaces.

[line-o]

Root cause is in eXist-db, not roaster: util:declare-option() resolves the prefix of the option name against the root (main module) context, not against the static context of the library module making the call. That is why router.xql cannot declare the output prefix itself, and why the consuming main module has to carry the seemingly unused declare namespace output=….

Details, repro and a fix sketch are in eXist-db/exist#6668.

Note that the fn:QName / EQName idea does not work either: util:declare-option("Q{http://www.w3.org/2010/xslt-xquery-serialization}method", "json") is rejected by eXist with XPST0081: options must have a prefix, and util:declare-namespace() from within the library module only binds the prefix in the module's own context. So until #6668 is fixed there is no clean way for roaster to avoid the declaration in the consumer.