Add recalc to xlsxC.getValueFrom()

[mikeschinkel]

PR Details

Adds a maybeRecalc() method to address the issue mentioned discussion #1822.

Description

Adds a maybeRecalc() method to xlsxc to be called immediately after entering the getFromValue() method.
This calls File.CalcCellValue() when xlsxc.F != nil and xlsxc.R != "" and xlsxc.V not one of "", 0, or 0.0.

This is a draft PR with many TODOs that bring up questions I had about if I was doing this the best way. I also ask questions to ensure I am using the right internal features and if I am following the vision of the project.

NOTE, when I was about to submit this I read the checklist and then went through the very thorough contributing guidelines.

Alas, I realizes there are many things I did not do — and since I am already running bind on my other deadlines I don't have time to do them all right now.

So I could have chosen either to not submit this as a draft PR — as I wrote it to solve my own current issues — or submit it so that it could be reviewed in connection with the referenced discussion and possibly updated to turn into a non-draft PR that could be merged later.

I chose the latter. I hope that you agree with me that I made the right choice.

Related Issue

Discussion #1822.

Motivation and Context

Ensures that zero values are not returned for sheets where there is a formula and a zero value, and while Excel shows a value excelize otherwise returns a zero value because of what is in the <v> element.

This issue surfaces when calling File.GetRows(), and maybe other methods.

I wrote this fix to meet my own needs, and am submitting it as a draft PR rather than just keeping it to myself.

How Has This Been Tested

I have only done manual testing as it is only a draft PR meant to spur discussion.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document.