Cannot read property 'map' of null about jupyterlab_voyager HOT 3 OPEN

Thx for reporting this issue!
It looks like a file content reading error. For local file, the content reading process relies on "read" method from vega-loader(). It loads the content into strings and process them with different delimiters based on different file types. Therefore, to use this method properly, we have to make sure the file contents strictly match the file type.

Those errors are likely to be caused by file type&content conflicts. You may obtain and test some more files from here (https://vega.github.io/vega-lite/examples/bar.html) to see if it's the case.

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Thanks for your reply!
I play around with it and finally find out the reason.
My .csv file's first column is index column and it does not have a header name. So that element of the header line is simply blank. After I fill some text to it and reload the data, it works.
Is it an issue you can fix? Thanks!

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Thanks for sharing the info.
I can't really change the "read" method there, but I will try some other ways to see if it can help.

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