Breaking interaction between dynamic lists and tables

[Skaiir]

Describe the Bug

This form apparently breaks form-js

{
  "components": [
    {
      "label": "Table",
      "type": "table",
      "layout": {
        "row": "Row_191hb77",
        "columns": null
      },
      "dataSource": "=Field_0r3jms4",
      "rowCount": 3,
      "id": "Field_0r3jms4",
      "columns": [
        {
          "label": "ID",
          "key": "id"
        },
        {
          "label": "Name",
          "key": "name"
        },
        {
          "label": "Date",
          "key": "date"
        }
      ]
    },
    {
      "label": "Number",
      "type": "number",
      "layout": {
        "row": "Row_0dbmu1z",
        "columns": null
      },
      "id": "Field_0fsxs1b",
      "key": "idfilter",
      "defaultValue": 2
    },
    {
      "components": [
        {
          "components": [
            {
              "text": "{{this.id}}",
              "label": "Text view",
              "type": "text",
              "layout": {
                "row": "Row_06z1kim",
                "columns": null
              },
              "id": "Field_0kypubr"
            },
            {
              "label": "Number",
              "type": "number",
              "layout": {
                "row": "Row_0dx6ob8",
                "columns": null
              },
              "id": "Field_0kzopb8",
              "key": "id"
            },
            {
              "label": "Text field",
              "type": "textfield",
              "layout": {
                "row": "Row_1el0dpw",
                "columns": null
              },
              "id": "Field_1jpezr9",
              "key": "name"
            },
            {
              "label": "Text field",
              "type": "textfield",
              "layout": {
                "row": "Row_0sr7lrz",
                "columns": null
              },
              "id": "Field_0ahpidx",
              "key": "date"
            }
          ],
          "showOutline": true,
          "label": "Group",
          "type": "group",
          "layout": {
            "row": "Row_1dr2rq5",
            "columns": null
          },
          "id": "Field_1s20g9l",
          "conditional": {
            "hide": "=this.id < idfilter"
          }
        },
        {
          "label": "Separator",
          "type": "separator",
          "layout": {
            "row": "Row_1q2u5mi",
            "columns": null
          },
          "id": "Field_1uzwox6"
        }
      ],
      "showOutline": true,
      "isRepeating": true,
      "allowAddRemove": true,
      "defaultRepetitions": 1,
      "label": "Dynamic list",
      "type": "dynamiclist",
      "layout": {
        "row": "Row_1w1xmo6",
        "columns": null
      },
      "id": "Field_0596cy3",
      "path": "Field_0r3jms4",
      "nonCollapsedItems": null
    }
  ],
  "type": "default",
  "id": "Form_1je5j4d",
  "executionPlatform": "Camunda Cloud",
  "executionPlatformVersion": "8.4.0",
  "exporter": {
    "name": "Camunda Modeler",
    "version": "5.20.0"
  },
  "schemaVersion": 15
}

Steps to Reproduce

• Load the following form into the playground

Expected Behavior

• Form should load without error

[Skaiir]

The issue as far as I understand it:

There is some faulty interaction somewhere between the table's data initialization and the dynamic list leading to an element of the array to be dropped (element 0 becomes empty). This messes with the chunking logic for the table as we use reduce, which ends up starting at index 1, leading to an error.

Soft fix would be to filter the array of empty elements in the chunking logic.
Still have to figure out where and why that initial element is getting wiped, but that would be the true fix, not having the element become empty.

[Skaiir]

More investigations: there is something very strange going on with the data context where the id is somehow an array in this scenario.

[Skaiir]

May be related to #1085

Actually a separate issue. Although the above issue was interfering with the fixing of this one.

RCA

Conditional hiding logic on dynamic list group causes deletion of the array element in the working state, the thing is the way the array element is deleted is not via removing the element from the array, but rather by setting it to an empty element, so we end up with arrays of the form [ <empty>, element 2, element 3 ].

The chunking logic of the table makes use of reduce, as previously mentioned, but because the empty element is present, the indexes used in reduce are offset, which breaks the reduction logic.

So I'm not sure what the fix here is, the way I see it either we make sure that we don't create these empty elements, but I believe this will cause issues with the rendering of the dynamic list. Another option that may keep the hierarchy intact would be to create null values, but then we will need to filter those out on submit. The simplest fix would be to filter out empty elements from the table data source. I'll try this out.

[Skaiir]

Fixed via #1088