Small float does not get parsed correctly

[edhaz]

Description

Parsing of a float ends up as a string. Number Format has no effect on it.

Steps to reproduce the issue:

1. .xlsx file with 1 sheet with 0.00004 in cell A1 (General cell type).
2. Attempt to change the style using "custom_number_format"

numberFmt := "0.00000"
styleID, err := output.NewStyle(&excelize.Style{CustomNumFmt: &numberFmt})
if err != nil {
    fmt.Println(err)
}
if err := output.SetCellStyle(sheetName, "A1", "A1", styleID); err != nil {
    fmt.Println(err)
}

3. Get Rows from the sheet

Describe the results you received:
4.0000000000000003E-5

Describe the results you expected:
0.00004

Output of go version:

go version go1.17.1 darwin/arm64

Excelize version or commit ID:

v2.4.1

Environment details (OS, Microsoft Excel™ version, physical, etc.):
macOS Big Sur 11.5.2
Microsoft Excel for Mac v16.53

[xuri]

Thanks for your feedback, I'm sorry that this library doesn't support parse custom number format and some scientific notation numeric with the default number format currently, it will return the raw value of the cell. Please try to convert it by yourself with cell type into your need format, for example:

num, err := strconv.ParseFloat("4.0000000000000003E-5", 64)
if err != nil {
    fmt.Println(err)
}
strconv.FormatFloat(num, 'f', -1, 64)

This issue also affects the time parse precision, also ref #1030, I'll fix it later.

[edhaz]

Thanks for all your work on this! 😄