Fix read this.worksheet before assign it

[ZyqGitHub1]

The anchor.js assign this.worksheet = worksheet at end of constructor, but the getter (such as rowHeight) used in constructor will read this.worksheet. so it will cause rowHeight fall back to default value (180000);

Summary

When I want to add a image in a cell over a range, and I adjust the height of this row before. The nativeRowOff will not calculate use the row height.

const Excel = require('exceljs');
const fs = require('fs').promises;

(async () => {
    const workbook = new Excel.Workbook();
    await workbook.xlsx.readFile('./test.xlsx');
    const worksheet = workbook.getWorksheet(1);
    const row = worksheet.getRow(1);
    row.height = 400;
    const col = worksheet.getColumn('A');
    col.width = 200
    const image = await fs.readFile('./image.png')
    const imageId = workbook.addImage({
        buffer: image,
        extension: 'png',
    });
    worksheet.addImage(imageId, {
        tl: { col: 0.5, row: 0.5 },
        br: { col: 1, row: 1 }
    });
    await workbook.xlsx.writeFile('./result.xlsx');
})()

result is

Test plan

After I change anchor.js,

const Excel = require('exceljs');
const fs = require('fs').promises;

(async () => {
    const workbook = new Excel.Workbook();
    await workbook.xlsx.readFile('./test.xlsx');
    const worksheet = workbook.getWorksheet(1);
    const row = worksheet.getRow(1);
    row.height = 400;
    const col = worksheet.getColumn('A');
    col.width = 200
    const image = await fs.readFile('./image.png')
    const imageId = workbook.addImage({
        buffer: image,
        extension: 'png',
    });
    worksheet.addImage(imageId, {
        tl: { col: 0.5, row: 0.5 },
        br: { col: 1, row: 1 }
    });
    await workbook.xlsx.writeFile('./result.xlsx');
})()

the result is

The image top-left will start from 0.5*row height

Related to source code (for typings update)

https://github.com/ZyqGitHub1/exceljs/blob/458f372609589e6b3665a5c955998b677df2037e/lib/doc/anchor.js#L7

[Siemienik]

Good catch! LGTM 🥇

[hfhchan-plb]

This change means that all of the existing images are now off because the actual row height and col width are now being used. The previous behaviour was arguably a bug, but this is a breaking change causing every single image to be positioned differently.

[hfhchan-plb]

There really should be an API which allows us to do actual absolute positioning, i.e. fixed pixel offset from the cell or fixed pixel offset from top left of spreadsheet, instead of the current absolute positioning which is more like relative.