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kotlinlang

How can I make a lens to extract a possibly empty list of values from form data? I tried this:
```val idsField = FormField.string().multi.optional("ids")
val idsLens = Body.webForm(Validator.Ignore, idsField).map { idsField(it) }.toLens()```
but if the form data is empty, I get this error:
```org.http4k.lens.LensFailure: formData 'ids' is required
	at org.http4k.lens.BodyLensSpec$toLens$1$1.invoke(body.kt:50)
	at org.http4k.lens.BodyLensSpec$toLens$1$1.invoke(body.kt:50)
	at org.http4k.lens.BodyLens.invoke(body.kt:19)```


I came up with this workaround:
```val idsField = FormField.string().multi.required("ids")
val idsLens =
    Body.webForm(Validator.Ignore, idsField).map { if (it.fields.containsKey("ids")) idsField(it) else emptyList() }
        .toLens()```

Instead of having a multi field, would merging them into a single csv field be acceptable?

```val field = FormField.csv().optional("my_field")```

Not really, that would complicate the htmx based front end unnecessarily.
<https://htmx.org/examples/bulk-update/>

Then I rather stick with my workaround (see above).