I was having some problem with chart.js legend. The legend with long text took up too much spaces which resulting in the reduce in the size of my pie chart:
Another
Long legend nowrap is a known issue check https://github.com/chartjs/Chart.js/issues/3641
May be they can cover it in next releases. For now the solution is to remove the native legend and draw your custom one
I've created this plunk as an example for doghnut chart with custom legend https://embed.plnkr.co/5nuGS2KEV6hvESwGrOse/