TypeError: easingFunction is not a function

[aldipower]

Sometimes, when I reload or resize the window with a chart included, Chart.js throws the following error:
TypeError: easingFunction is not a function

I could track it down to this line in the current 2.9.3 release render-function:

var easingFunction = helpers.easing.effects[animationObject.easing];
...
chart.draw(easingFunction(stepDecimal), stepDecimal, currentStep);

https://github.com/chartjs/Chart.js/blob/release/src/core/core.controller.js#L650

I notices that the upcoming version 3.0.0 has a completely rewritten animation handling.
But this will be a breaking changes release and I hope 2.9. will still receive some bugfixes.

Expected Behavior

Chart.js should not throw and break the complete application,
instead it should catch the error and write an console.error-message.

Possible Solution

Implement a null-check and do not try to execute the easingFunction.

Steps to Reproduce (for bugs)

Render a chart (Pie, Bar, Line) and resize the window wildly.

    this.chartOptions = {
      responsive: true,
      maintainAspectRatio: false,
      legend: false,
    };

I turned off animations globally:

  global.animation = {
    duration: 0,
  };

  global.hover = {
    animationDuration: 0,
  };

  global.responsiveAnimationDuration = 0;

Environment

• Chart.js version: 2.9.3
• Browser name and version: Firefox Nightly (Mar 2020)

[benmccann]

Hmm. Maybe this is related to the way you disabled animations? What if you disable animations like this? https://www.chartjs.org/docs/latest/general/performance.html#disable-animations

[aldipower]

Hey, same thing when disabling animation directly in the chart options, like in the link, you've posted.
Chart.js crashes hard with an unhandled exception when I resize then window, but not every time, only sometimes. Looks like a timing thing dunno.
But still it is not good practice to call a function that could possibly went 'null'. There is a null-check missing anyway..
Too bad you closed the PR, because I am not sure, if everybody wants to update to a new major version with a lot of rewrites and potential new bugs.