Support csv-external for defining an external instance not necessarily used for a select

[ggalmazor]

getodk/xforms-spec#88 introduces a new external itemsets in csv feature to the specs. This has been already implemented in JavaRosa with getodk/javarosa#397 and it looks like we could implement this in PyXForm now too.

[lognaturel]

I'm pretty sure using secondary external CSV instances as itemsets already works using select_one_from_file/select_multiple_from_file. However, the resulting XML needs some manual edits because of #286. Does that sound right, @MartijnR?

Perhaps the "todo" here is to add type=csv-external by analogy to #107

[MartijnR]

However, the resulting XML needs some manual edits because of #286.

Yes indeed.

Perhaps the "todo" here is to add type=csv-external by analogy to #107

Yes, I agree.

[MartijnR]

Everybody still on board with adding csv-external (similar to the existing xml-external)?

There are a bunch of cases that could result in an XML and CSV instance to be added with the same id. I think those should all output an error and fail to transform (as they currently do for similar situations using xml-external and select_..._from_file)

• xml-external and csv-external are both present and have the same name
• csv-external | somefile and select_one_from_file somefile.xml
• csv-external | somefile and select_multiple_from_file somefile.xml

[MartijnR]

Oops, I see there is a PR already but it appears to be abandoned. It could perhaps serve as a base for a new PR.