PivotTable: Support multiple values

[Rablet]

Summary

This adds support for multiple values in pivot tables.
It also allows not supplying any columns. This mimics the built-in Excel functionality where it populates the columns field with "Values".

Limitation: It is not currently possible to provide multiple values AND any columns.

With the first implementation checked in yesterday it is not possible to use multiple values. This PR removes that limitation (as long as custom columns are not used)

Test plan

I created a PivotTable with multiple values and no columns without problems.
I crated a PivotTable with one value and multiple columns without problems

[Siemienik]

@Rablet Thank you for development that, for more implementation details you can drive into #2575 :)

From my end, I required tests which proves and concrete the behaviour in the future. Would you like to add it?

Thanks 👍

[Rablet]

Absolutely! Please see below:

1: Multiple values, no columns:

const ExcelJS = require('exceljs');

const createWorkbook = async () => {
    const workbook = new ExcelJS.Workbook();
    workbook.calcProperties.fullCalcOnLoad = true;

    const worksheet1 = workbook.addWorksheet('Sheet1');
    worksheet1.addRows([
        ['Description', 'Initial Cost', 'VAT', 'Total',],
        ['Potatoes', 10, 2, 12],
        ['Potatoes', 10, 2, 12],
        ['Potatoes', 10, 2, 12],
        ['Grapes', 20, 4, 24],
        ['Grapes', 20, 4, 24],
        ['Strawberries', 15, 3, 18],
    ]);

    const worksheet2 = workbook.addWorksheet('Sheet2');
    worksheet2.addPivotTable({
        sourceSheet: worksheet1,
        rows: ['Description'],
        columns: [],
        values: ['Initial Cost', 'VAT', 'Total'],
        metric: 'sum',
    });

    await workbook.xlsx.writeFile("PivotWithMultipleValues.xlsx");
}
createWorkbook();

2: Attempt with multiple values & columns:

 worksheet2.addPivotTable({
        sourceSheet: worksheet1,
        rows: ['Description'],
        columns: ['Description', 'Initial Cost'],
        values: ['Initial Cost', 'VAT', 'Total'],
        metric: 'sum',
    });

Output:

Warning: Pivot Table support is experimental. 
Please leave feedback at https://github.com/exceljs/exceljs/discussions/2575
/Users/robin/dev/exceljs/lib/doc/pivot-table.js:81
    throw new Error(
          ^

Error: It is currently not possible to have multiple values when columns are specified. Please either supply an empty array for columns or a single value.
    at validate (/Users/robin/dev/exceljs/lib/doc/pivot-table.js:81:11)
    at makePivotTable (/Users/robin/dev/exceljs/lib/doc/pivot-table.js:20:3)
    at Worksheet.addPivotTable (/Users/robin/dev/exceljs/lib/doc/worksheet.js:821:24)
    at createWorkbook (/Users/robin/dev/nodeexceldemo/index.js:21:16)
    at Object.<anonymous> (/Users/robin/dev/nodeexceldemo/index.js:31:1)
    at Module._compile (node:internal/modules/cjs/loader:1101:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)
    at node:internal/main/run_main_module:17:47

3: Showing that your scenario from the original PR still works:

const Excel = require('exceljs');

const workbook = new Excel.Workbook();

const worksheet1 = workbook.addWorksheet('Sheet1');
worksheet1.addRows([
    ['A', 'B', 'C', 'D', 'E'],
    ['a1', 'b1', 'c1', 4, 5],
    ['a1', 'b2', 'c1', 4, 5],
    ['a2', 'b1', 'c2', 14, 24],
    ['a2', 'b2', 'c2', 24, 35],
    ['a3', 'b1', 'c3', 34, 45],
    ['a3', 'b2', 'c3', 44, 45],
]);

const worksheet2 = workbook.addWorksheet('Sheet2');
worksheet2.addPivotTable({
    // Source data: entire sheet range; header in first row
    sourceSheet: worksheet1,
    // Pivot table fields: via header row in `worksheet1`
    rows: ['A', 'B'],
    columns: ['C'],
    values: ['E'], // Exactly 1 field
    metric: 'sum', // Metric: 'sum' only
});

workbook.xlsx.writeFile("RegressionTest.xlsx");

Please let me know if you'd like to see anything else.

[Rablet]

Are you all good with this PR or do you need something else?

[budaesandrei]

is this going to get merged anytime soon?