[Bug] axisLabel.formatter function (value, index) doesn't receive index numbers when using customValues

[mkf62]

Version

6.0.0

Link to Minimal Reproduction

https://echarts.apache.org/examples/en/editor.html?code=MYewdgzgLgBAHgNQIYBsCuBTCMC8MDaAjAAzEA0MhAHAMwUBM1FNLFALAOxUC6A3AFChIsOABkkAIwwpseRKkwQAdAFskABwAUmuAEpcAPngwAVDACsugfxDqoAS3C4YAb34x4AQTj2IALld3DxgoAE91DACAcgA3BQwosiCPJB8IUXswSMDg4IgACxAAdwCoACdMJNyPcAAtDDKQb18ASTAAEww4AMJkmABfKuDU3wAVe2AAawC3apgC4tKKjCHc4DRoEBVkdCwA-V2IPsG-kfTJaRm-j3XN7fj_eB3FVeCAMxAytSgoBoC3tBgYAOJyaOIoCiZTp6HJzGBCCAgFAYJQoEAAc00AAM2tCYL4AgASFxQrr9LFWa7BMoYKBoMpgeDiKQyfCkuDcJRQEAAZXKmUxlLm_WOQROHlCzUes2CYQi0XBmCiYqGEAa9j2BD6Mty7SQUCQAXwVI8RFIFEIADZiNxXrkiOZyDB6GwbXbgkRaBa2OZbSaCPRzc6aGw_XCA0xnfQeO7TfRzPRmMRCGG4fgaEHCD7U3N06wozQc9V0z6LeYOEX7ZwqAwODaqZWQuFslEUJkEqKPNx-P1eEA

Steps to Reproduce

If using customValues for axisTick and axisLabel on xAxis of type: 'value', the axisLabel.formatter callback function doesn't receive index and instead only receives value. See demo which has a console.log statement called in the formatter function to see the value of the index (nothing will actually load on the chart due to the error it encounters in the formatter, but if you comment out formatter the chart will load fine).

Current Behavior

index is undefined.

Expected Behavior

index has a value based on the array used for customValues.

Environment

- OS: MacOS Sequoia v15.6
- Browser: Chrome v139.0.7258.128
- Framework: React 18.2

Any additional comments?

The simple workaround (at least in my demo) is to just do

const xValues = [100, 183, 218, 333, 478];
const xLabels = xValues.map((x) => x * 5);

axisLabel: {
      customValues: xValues,
      formatter: function (value) {
        const idx = xValues.indexOf(value)
        return xLabels[idx].toString();
      }
}

but that defeats the purpose of the formatter callback that's supposed to receive the indexes.

[szymonpachucki]

Looking into it