Named repeat specs cause runtime error: "Duplicate data set name"

[marcprux]

Assigning a name (e.g., "Some Name") to a repeated spec will generate a vega spec containing children with non-unique names, thus raising an error "Duplicate data set name: "Some_Name_marks". This can be reproduced in the vega-lite editor by loading "Multi Series Line Chart with Halo Stroke" (line_color_halo.vl.json) and setting the repeated spec property: "name": "Some Name"

A simpler sample spec that shows this error:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.13.1.json",
  "data": {"values": [{}] },
  "repeat": {
    "layer": ["A","Z"]
  },
  "spec": {
    "layer": [{
      "name": "LAYERNAME",
      "mark": {"type": "point"}
    }
    ]
  }
}

This generates the following vega spec that has duplicate instances of "LAYERNAME_marks":

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "background": "white",
  "padding": 5,
  "width": 20,
  "height": 20,
  "style": "cell",
  "data": [{"name": "source_0", "values": [{}]}],
  "marks": [
    {
      "name": "LAYERNAME_marks",
      "type": "symbol",
      "style": ["point"],
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "transparent"},
          "stroke": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "point"},
          "x": {"signal": "width", "mult": 0.5},
          "y": {"signal": "height", "mult": 0.5}
        }
      }
    },
    {
      "name": "LAYERNAME_marks",
      "type": "symbol",
      "style": ["point"],
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "transparent"},
          "stroke": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "point"},
          "x": {"signal": "width", "mult": 0.5},
          "y": {"signal": "height", "mult": 0.5}
        }
      }
    }
  ]
}

The error in the console is:

Error: Duplicate data set name: "LAYERNAME_marks"
(anonymous function) — error.js:2
(anonymous function) — Scope.js:436
(anonymous function) — mark.js:130
forEach
(anonymous function) — scope.js:38
b — view.js:65
(anonymous function) — parse.js:12
initView — renderer.tsx:134
componentDidUpdate — renderer.tsx:257
os — react-dom.production.min.js:212:481
fu — react-dom.production.min.js:255:474
fu
(anonymous function) — scheduler.production.min.js:20:238
hu — react-dom.production.min.js:249:218
Js — react-dom.production.min.js:241
Js
(anonymous function) — react-dom.production.min.js:123:348
(anonymous function) — scheduler.production.min.js:20:238
Ki — react-dom.production.min.js:123:306
qi — react-dom.production.min.js:123:247
eu — react-dom.production.min.js:241:156
notify — Subscription.js:19
(anonymous function) — Subscription.js:92
(anonymous function) — Subscription.js:97
[native code]
m — redux.js:221
updateSpec — renderer.tsx:244
handleEditorChange — renderer.tsx:160:84
handleEditorChange
i — debounce.js:5
https://vega.github.io/schema/vega-lite/v4.13.1json

Perhaps repeat layer names could be additionally suffixed with the index or identifier of the child layer, so the layers in the above spec would generate distinct names like: "LAYERNAME_repeat_1_marks" and "LAYERNAME_repeat_2_marks"?

[marcprux]

Might this be related to https://github.com/vega/vega-lite/issues/4274?

[domoritz]

I think the issue may just be in the normalizer. It probably doesn't include the layered field in the name. Can you send a pull request to fix it?

[domoritz]

This is the normalized spec.

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.13.1.json",
  "data": {"values": [{}]},
  "layer": [
    {
      "layer": [
        {"name": "LAYERNAME", "mark": {"type": "point"}, "encoding": {}}
      ],
      "name": "child__layer_A"
    },
    {
      "layer": [
        {"name": "LAYERNAME", "mark": {"type": "point"}, "encoding": {}}
      ],
      "name": "child__layer_Z"
    }
  ]
}

I think people may need control over the children's names. However, since repeat can only be used for fields right now, I don't think we have a good solution.

I'm demoting this to P4 since it's an uncommon use case.

[ChiaLingWeng]

I think it's already fixed in v5.16.3