throwing an error in charts

[mikima]

Is it possible to throw an error from the chart to RAWGraphs interface? For example, in radar chart you should drop at minimum three dimensions to see something. Would be nice to tell it to the user

[bianchimro]

hi @mikima yes, it's possible by just throwing a js error in your render function

throw new Error("Hello error")

that renders like this:

There was a problem showing the error in the frontend, I just fixed it here
https://github.com/rawgraphs/rawgraphs-frontend/commit/9a539ce16c9b794c1675991f94e459b6bc932208
(still needs some styling, but there was a positioning issues and the error was sometimes hidden)

Your specific use case is covered by the dimensions api. When you declare a dimension, you can set minValues and maxValues properties (indipendently) to require/limit the maximum number of values that can be mapped on a multiple dimension.
Like:

export const dimensions = [
  {
    id: 'axes',
    name: 'spokes',
    validTypes: ['number'],
    required: true,
    multiple: true,
    minValues: 2,
    aggregation: true,
    aggregationDefault: {
      number: 'sum',
      string: 'csvDistinct',
      date: 'csvDistinct',
    },
  },
  ...
]

This should the way to do it but:

• It's not documented (sorry, working on this!)
• The frontend at the moment does not show this kind of error. This is a mapping error that forbids render, so it's not even shown under the artboard like the error in the screenshot above. We should decide if it should be shown here or in the mapping section.
  Personally, I'd show it in the mapped dimension, that is also much easier to implement at the moment

[mikima]

Great! Thanks