Avoid error on malformed address

[papandreou]

Hi, I've run into another weird Excel file that causes an error in exceljs:

TypeError: Cannot read property '0' of null
    at Object.decodeAddress (/Users/andreaslind/work/exceljs/lib/utils/col-cache.js:95:33)
    at Object.decodeEx (/Users/andreaslind/work/exceljs/lib/utils/col-cache.js:156:21)
    at /Users/andreaslind/work/exceljs/lib/xlsx/xform/book/workbook-xform.js:182:34
    at Array.forEach (<anonymous>)
    at Object.each (/Users/andreaslind/work/exceljs/lib/utils/under-dash.js:7:13)
    at module.exports.reconcile (/Users/andreaslind/work/exceljs/lib/xlsx/xform/book/workbook-xform.js:175:7)
    at module.exports.reconcile (/Users/andreaslind/work/exceljs/lib/xlsx/xlsx.js:91:19)
    at /Users/andreaslind/work/exceljs/lib/xlsx/xlsx.js:345:16
    at <anonymous>

The error is triggered by this xl/workbook.xml (slightly edited and pretty-printed):

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<workbook xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:x15="http://schemas.microsoft.com/office/spreadsheetml/2010/11/main" xmlns:xr="http://schemas.microsoft.com/office/spreadsheetml/2014/revision" xmlns:xr6="http://schemas.microsoft.com/office/spreadsheetml/2016/revision6" xmlns:xr10="http://schemas.microsoft.com/office/spreadsheetml/2016/revision10" xmlns:xr2="http://schemas.microsoft.com/office/spreadsheetml/2015/revision2" mc:Ignorable="x15 xr xr6 xr10 xr2">
  <fileVersion appName="xl" lastEdited="7" lowestEdited="6" rupBuild="10311"/>
  <workbookPr/>
  <xr:revisionPtr revIDLastSave="0" documentId="13_ncr:1_{C8FC9E1B-96BE-724A-A363-02D52AD78D60}" xr6:coauthVersionLast="31" xr6:coauthVersionMax="32" xr10:uidLastSave="{00000000-0000-0000-0000-000000000000}"/>
  <bookViews>
    <workbookView xWindow="260" yWindow="460" windowWidth="28280" windowHeight="15860" tabRatio="500" xr2:uid="{00000000-000D-0000-FFFF-FFFF00000000}"/>
  </bookViews>
  <sheets>
    <sheet name="Sheet1" sheetId="1" r:id="rId1"/>
  </sheets>
  <definedNames>
    <definedName name="_xlnm._FilterDatabase" localSheetId="0" hidden="1">Sheet1!$A$1:$V$121</definedName>
    <definedName name="_xlnm.Print_Area" localSheetId="0">Sheet1!$B:$F</definedName>
  </definedNames>
  <calcPr calcId="179017" concurrentCalc="0"/>
</workbook>

Specifically Sheet1!$B:$F. The fragments are passed to colCache.decodeAddress, which assumes that there's a row number in each of the references ($B and $F). I can't tell if this syntax is legal or not -- I don't really know much about the .xlsx file format.

I tried to create a spec that triggers the error, but it seems that basing it off
scenarios in https://github.com/guyonroche/exceljs/blob/master/spec/unit/xlsx/xform/book/workbook-xform.spec.js doesn't work as that does not exercise the reconciliation phase.

The enclosed change avoids the error by making decodeAddress do a "best effort" when handed this kind of weird reference. I honestly don't know if that is the right way to go about it.

Unfortunately, I'm unable to share the original .xlsx file that triggered the error.

[papandreou]

The <definedName name="_xlnm.Print_Area" localSheetId="0">Sheet1!$B:$F</definedName> element survives a load->save roundtrip through Excel for Mac 16.12, so it doesn't seem like this one is due to a bad 3rd party integration.

[guyonroche]

@papandreou this is a good catch. I've just added an integration test using an Excel generated file based on your description - just create a Hello World spreadsheet with a print area set to $B:$F and boom!
Will merge now and publish :-)