[Feature] legend.data.shape优先级应该高于legend.item.symbolType

[skie1997]

What problem does this feature solve?

当前表现：
主题中的legend.item.style.symbolType优先级高于legend.data.shape.symbolType，导致用户自定义shape失效

spec：

const spec = {
  type: 'bar',
  data: [
    {
      id: 'barData',
      values: [
        { type: 'Autocracies', year: '1930', value: 129 },
        { type: 'Autocracies', year: '1940', value: 133 },
        { type: 'Autocracies', year: '1950', value: 130 },
        { type: 'Autocracies', year: '1960', value: 126 },
        { type: 'Autocracies', year: '1970', value: 117 },
        { type: 'Autocracies', year: '1980', value: 114 },
        { type: 'Autocracies', year: '1990', value: 111 },
        { type: 'Autocracies', year: '2000', value: 89 },
        { type: 'Autocracies', year: '2010', value: 80 },
        { type: 'Autocracies', year: '2018', value: 80 },
        { type: 'Democracies', year: '1930', value: 22 },
        { type: 'Democracies', year: '1940', value: 13 },
        { type: 'Democracies', year: '1950', value: 25 },
        { type: 'Democracies', year: '1960', value: 29 },
        { type: 'Democracies', year: '1970', value: 38 },
        { type: 'Democracies', year: '1980', value: 41 },
        { type: 'Democracies', year: '1990', value: 57 },
        { type: 'Democracies', year: '2000', value: 87 },
        { type: 'Democracies', year: '2010', value: 98 },
        { type: 'Democracies', year: '2018', value: 99 }
      ]
    }
  ],
  xField: ['year', 'type'],
  yField: 'value',
  seriesField: 'type',
  legends: {
    visible: true,
    orient: 'top',
    position: 'start',
    data: item => {
      return item.map(i => {
        console.log('i', i)
        return {...i, shape: {...i.shape, symbolType: 'rect'}}
    })
    }
  }
};

const theme = {
    background: 'rgba(12,9,41,1)',
    component: {
      axis: {
        grid: {
          visible: true,
          style: {
            stroke: 'rgba(255,255,255,0.15)',
            lineWidth: 1
          }
        },
        label: {
          visible: true,
          style: {
            angle: 0,
            fill: 'rgba(255,255,255,0.65)',
            fontFamily: 'D-DIN',
            fontSize: 12,
            fontWeight: 'normal'
          }
        },
        domainLine: {
          visible: false,
          style: {
            stroke: 'rgba(0,0,0,0)'
          }
        },
        title: {
          visible: false
        }
      },
      crosshair: {
        xField: {
          line: {
            style: {
              opacity: 0.2
            }
          }
        }
      },
      tooltip: {
        backgroundColor: 'rgba(0,0,0,0.8)',
        panel: {
          backgroundColor: 'rgba(0,0,0,0.8)'
        },
        titleLabel: {
          fontColor: 'rgba(255,255,255,0.65)'
        },
        keyLabel: {
          fontColor: 'rgba(255,255,255,0.65)'
        },
        valueLabel: {
          fontColor: 'rgba(255,255,255,0.65)'
        }
      },
      discreteLegend: {
        item: {
          shape: {
            style: {
              symbolType: 'circle'
            }
          }
        }
      }
    }
  };



 VChart.ThemeManager.registerTheme('user', theme);
VChart.ThemeManager.setCurrentTheme('user');


const vchart = new VChart(spec, { dom: CONTAINER_ID });
vchart.renderSync();
window['vchart'] = vchart;

What does the proposed API look like?

null