setData mutating source array

[mjyeaney]

Seeing a strange behavior against Highcharts 4.1.5. When providing an Array of numbers (i.e, [1,2,3,4]), after some threshold the source array seems to be mutated into the following form:

[{y = 1}, {y=2}, {y=3}, {y=4}]

This seems to happen on larger sets of data (1300 - 1400 points + ), but we can't seem to get turboThreshold or cropThreshold to make a difference. Is there a setting we're missing, or is this a known bug?

Normally not an issue, but we're visualizing running time-series data windows and as a result are hanging on to the arrays we're calling setData() with. Once they are mutated, they are effectively "broke"...upstream sorting/binning code doesn't expect the inner objects, and stops working.

Thanks for your help!

[mjmckp]

I'm seeing this as well

[TorsteinHonsi]

Can you provide a demo? I set up a test case, but even when running 10 000 points the numbers are preserved in the original array.

[mjyeaney]

I created a trimmed-down version of the basic approach we're using [http://jsfiddle.net/LLExL/4807/]. However, as I mentioned, I can't trigger the exact use case (nor could I before). The only remaining significant difference between this example and the real code is there are 8 - 10 graphs (4 - 5 pairs just like the demo).

Can you see any issues with the approach shown that may cause issues?

[TorsteinHonsi]

There is one workaround that should be valid under any circumstance - if you copy (splice) the array before running setData, you are sure it isn't modified:

series.setData(myData.splice(0));

[andylash]

Don't have a reliable repro either, but we also see this in 4.1.6. It seems to happen on certain charts with certain data, which doesn't make any sense.

[vickychijwani]

This seems related to #4701 / #3604, which are presumably fixed in the next version (likely v4.1.10).

[LinGG]

here is the demo. http://jsfiddle.net/xq29x6ja/3/

p.s. seems it is nothing about turboTreshold

[TorsteinHonsi]

Demo http://jsfiddle.net/highcharts/xq29x6ja/4/

[TorsteinHonsi]

@pawel: Consider the fiddle above.

Like we talked about earlier, creating a copy of of the source data is expensive, especially when dealing with a large amount of data. A leaner solution would be to identify the places where the source data is mutated, and do the copy there. Like in the case above, it is fixed by creating a copy in point.update:

Find this code:

            // Record the options to options.data. If there is an object from before,
            // use point options, otherwise use raw options. (#4701)
            seriesOptions.data[i] =  (isObject(seriesOptions.data[i]) && !isArray(seriesOptions.data[i])) ? point.options : options;

Before it, add this code:

            // If this is the first time we're writing back to options.data, create
            // a copy so that we don't mutate the source array. (#4259)
            if (!seriesOptions.data.isCopy) {
                seriesOptions.data = seriesOptions.data.slice();
                seriesOptions.data.isCopy = true;
            }

What do you think? And do you have other cases of data source mutation where this fix doesn't work?

[pawelfus]

The most popular are ones with setData() and when recreating the chart. I setup two use cases:

• recreate chart with the same main object: https://jsfiddle.net/3q19s1pz/9/ (hide first one of the series, click top tab, go back to the first tab -> series is deselected) (highcharts.local version: https://jsfiddle.net/oa8j64x1/ ). series.visible is polluted, it may be a different issue though.
• using setData(): http://jsfiddle.net/myvv9by5/2/ (highcharts.local version: http://jsfiddle.net/0gezvf8a/ ) - as I remember, slice() will make a copy only for arrays, not objects

[TorsteinHonsi]

Yes, the first case is a different issue, but it raises another question. If we don't want to mutate the input options at all, it will require a wide range of changes in our source code. For example, the exported chart is based on the idea that the configuration options are mutated and kept in sync with the state of the chart.