fix(line): 过滤空节点, 避免阶梯线条变为斜线

[Gyyi]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

fix that connectNulls with stepLine fails when after a long number of null entries occur

Fixed issues

#16424

Details

option:

option={
          title: {
            text: 'Step Line',
          },
          tooltip: {
            trigger: 'axis',
          },
          legend: {
            data: ['Step Start', 'Step Middle', 'Step End'],
          },
          grid: {
            left: '3%',
            right: '4%',
            bottom: '3%',
            containLabel: true,
          },
          toolbox: {
            feature: {
              saveAsImage: {},
            },
          },
          xAxis: {
            type: 'category',
            data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'],
          },
          yAxis: {
            type: 'value',
          },
          series: [
            {
              name: 'Step Start',
              type: 'line',
              step: 'start',
              connectNulls: true,
              data: [120, 132, 101, 134, 90, 230, 210],
            },
            {
              name: 'Step Middle',
              type: 'line',
              step: 'middle',
              connectNulls: true,
              data: [220, 282, null, 234, null, 430, 410],
            },
            {
              name: 'Step End',
              type: 'line',
              step: 'end',
              connectNulls: true,
              data: [450, 432, null, null, 590, 530, 510],
            },
          ],
        }

Before: What was the problem?

After: How is it fixed in this PR?

Misc

• The API has been changed (apache/echarts-doc#xxx).
• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

N.A.

Others

Merging options

• Please squash the commits into a single one when merging.

Other information

[echarts-bot]

Thanks for your contribution!
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[pissang]

The code looks good to me now. Could you add a test case line-step with npm run mktest command?

[pissang]

Seems it may not work when there are multiple consecutive NaN values. And handling these consecutive NaN values may be too complex and easy to bring bugs.

Perhaps the original filter logic is simpler and more robust. Sorry for the wrong suggestion.

But still the variable name points_ should be renamed to some others without underline, like newPoints.

[Gyyi]

Haha, OK, I have fixed this problem. And I also make it filter null points only when using connectNull: true.
Please review the code again，Thanks～

[echarts-bot]

Congratulations! Your PR has been merged. Thanks for your contribution! 👍