empty collection defaults break PATCH functionality

[haywood]

when specifying an operation like

                {
                    "method": "PATCH",
                    "path": "/:vendor_guid/:number",
                    "body": { "type": "item_patch" },
                    "description": "Upsert an item. Updates the item for the supplied vendor guid and number, creates it if one does not exist.",
                    "responses": {
                        "200": { "type": "item" },
                        "201": { "type": "item" },
                        "409": { "type": "[error]" }
                    }
                },

                },

given the below definition of item_patch

        "item_patch": {
            "description": "Used to PUT or PATCH an item.",

            "fields": [
                { "name": "quantity", "type": "long", "required": false },
                { "name": "prices", "type": "prices", "required": false },
                { "name": "attributes", "type": "[attribute]", "required": false },
                { "name": "return_policy", "type": "return_policy", "required": false },
                { "name": "metadata", "type": "[metadata]", "required": false },
                { "name": "identifiers", "type": "[identifier]", "required": false },
                { "name": "dimensions", "type": "[dimension]", "required": false },
                { "name": "content", "type": "[content]", "required": false },
                { "name": "images", "type": "[media]", "required": false },
                { "name": "videos", "type": "[media]", "required": false }
            ]
        },

one would expect that a field which is omitted from the patch would not be changed. However, due to the current default values for collection fields in both ruby and scala, the client generates empty collections that override the field to empty when sent to the server.

[haywood]

My proposal would be to generate Option[Coll[T]] in scala (e.g. Option[Seq[T]]) and default those fields to None (as we already do for Options). In ruby I would propose making the field nullable.

[haywood]

This issue is related to apicollective/apibuilder#293

[rcaloras]

👍

Didn't look like this included stuff for #7 does it? Want me to take a crack at that?