Select options query fails in case of non string attribute

[connoratrug]

How to Reproduce

• Create a Entity with a mref attr ( Person{ id: int, fav-color: mref}
• Create a Entity to refer to with a non string attribute ( Color{ id: int, label: string})
• Add some values to the entity that is referred to ( [{1, 'red'}, {2, 'blue'}]
• Add / Update the entity using multiSelect element ( used in Data row edit of Settings plugin), type a search query into the select box to filter the options ( b.v. "re"

Expected behavior

Sever returns filtered reference items ( {1, 'red'} in the example)

Observed behavior

Request to server fails and a js error is generated

(note: the default options query generated by the molgenis-ui-forms.MappingService incorrectly assumes columns used in options query are of type string / OR api incorrectly tries to query non string column as string column)

[fdlk]

Am typing it into the Vue Forms Specification document to make sure it's persisted, but so far I have:

• For attributes of type XREF or MREF, the user can select reference values from a pulldown. If values are already selected, and no search term is entered, the pull down is filled with the already selected values in the order of selection.
• The lookup attributes of the referenced entity type will be searched and results will be sorted on the first lookup attribute.
• The operator used for the search is EQUALS(==) for numerical and date / datetime types and SEARCH(=q=) for others. One single lookup attribute’s value has to match all of the specified search terms.
• The first 25 matching results are shown with an option to go to the next page

Lookup attributes

The lookup attributes of an entity are returned by the metadata in the REST api. They are all attributes of the entity itself (including inherited attributes), for which lookupAttribute = true. If an entity type has no lookup attributes, its label attribute is the lookup attribute. See the “Filters - lookup attributes” test cases in the data explorer test plan.

[fdlk]

See also existing implementations in jquery and react