PowerShell: The last cell of an empty column read by `ConvertFrom-Csv` is inconsistently `$Null`

@iRon7 These are obvious code snippets. The right question is whether there are popular applications or services that create such corrupted files that could lead to code like yours. I don’t know of any. And I can’t think of a reason why they would be created. From this I conclude that we should get rid of nulls.

I tend to think that nulls make no sense at all for CSV.

$a = @{q = $null}
$a | convertTo-Csv
"q"

ConvertTo-Csv: Object reference not set to an instance of an object.

It is a bug we must fix. But no null literals are in CVS format. So we have to output empty string. Then we could conclude it makes no sense to designate nulls and empties on read too. This looks more consistent.

Not valid CSV?

$Data = ConvertFrom-Csv @'
Id,Name,Note
01,John
02,Jack
03,Ryan,Just a note
04,Luke
05,Noah
'@

$Data.Note.ForEach{ $_ ? 'String' : 'Null' }

<#
Null
Null
String
Null
Null
#>

Still reproduces in: PS>$PSVersionTable

Name Value

PSVersion 7.3.9 PSEdition Core GitCommitId 7.3.9 OS Microsoft Windows 10.0.22621 Platform Win32NT PSCompatibleVersions {1.0, 2.0, 3.0, 4.0…} PSRemotingProtocolVersion 2.3 SerializationVersion 1.1.0.1 WSManStackVersion 3.0

@dkaszews Thanks! It is not a scenario we should care.

@iSazonov From original example, it should be String, Null, String, String - default value if there is a comma but value is empty, null if there are not enough commas so some columns are completely missing. We are focusing on the last column, but this should apply to every one:

$Data = ConvertFrom-Csv @'
Id,Note,Name
01,,John
02,
03,Just a note,Ryan
04,,Luke
'@

The way I see it, first you split on the delimiter, which gives you array of potentially empty values, then pad with nulls to correct length. With the examples present, it somehow also depends on the very presence of another row after, so reordering rows or truncating the table can change types.