[BUG][SCALA] instantiationType array is missed in Scalatra generator

[chameleon82]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
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Scalatra server template generating wrong default value new null[]() instead of 'List[String].emptydue missedarray` instantiationType

Description

openapi-generator version

2.3.0-SNAPSHOT

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml

Command line used for generation

Steps to reproduce

regenerate scalatra server - default value has incorrect value new null[](). should be List[String].empty

Related issues/PRs

Related code 25036e4#diff-62e3a15550247bb6a76bdc7745faa850R265

Suggest a fix

Add instantiationTypes.put("array", "List"); at abstract level or per template if array has specific meaning

@jimschubert

[jimschubert]

Hm. This existed when I stepped through the code last. I wonder if I forgot to commit or if it came from DefaultCodegen and has since been removed. Or maybe it was only defined in a derived generator.

I imagine we'd have the same issue for all OpenAPI types which should not be Java types and really shouldn't rely on DefaultCodegen to "do the right thing" (like map should instantiate with immutable Map by default).