Formatting system: format large numbers with thousands separators (digit grouping) by default

Summary of the new feature/enhancement

The output formatting system’s purpose is to present data to the human reader. (As such - because the formatted output isn’t meant for programmatic processing - it isn’t part of PowerShell’s breaking-changes contract.)

Currently, large numbers are output without thousands separators, i.e. without grouping the digits for easier comprehension.

I suggest applying this grouping to all numbers (that aren’t explicitly formatted via formatting data):

# WISHFUL THINKING - but you can get a preview with the prototype below.

# Number by itself (out-of-band formatting)
PS> 1000
1,000

# Implicit in-band formatting (table or list)
PS> @{ num = 1000 }

Name                           Value
----                           -----
num                            1,000

# Should also automatically apply to types with explicit formatting data 
# (unless number formatting is part of a given list item / table column).
# Note the "Size" column.
PS> Get-Item $PROFILE

    Directory: /Users/jdoe/.config/powershell

UnixMode   User             Group                 LastWriteTime           Size  Name
--------   ----             -----                 -------------           ----  ----
-rw-r--r-- jdoe             staff              10/23/2019 22:31           1,934  Microsoft.PowerShell_profile.ps1

As @ThomasNieto proposes below, a new preference variable and new switch for the Format-* cmdlets could allow opting into the old behavior. E.g.: $PSThousandsGrouping with values $true and $false (default $true), and switch -ThousandsGrouping.

Proposed technical implementation details (optional)

Here’s a quick prototype that uses the ETS. It is not the suggested implementation, for reasons of both performance and also changing the behavior of explicit .ToString() calls.

A proper implementation would require modifying the formatting system itself.

# Prototype:
[int16], [int], [long], [double], [decimal], [bigint], [uint16], [uint], [uint64] | % {

  Update-TypeData -TypeName $_.FullName  -MemberType ScriptMethod -MemberName ToString -Value { 
    # Determine how many decimal places there are in the original representation.
    # Note: PowerShell's string interpolation uses the *invariant* culture, so '.'
    #       can reliably be assumed to be the decimal mark.
    $numDecimalPlaces = ("$this" -replace '^[^.]+(?:.(.+))?', '$1').Length

    # Format with thousands grouping and the same number of decimal places.
    # Note: This will create a culture-sensitive representation
    #       just like with the default output formatting.
     # CAVEAT:
     #  To avoid a crash (from infinite recursion?), both .psobject.BaseObject 
     #  and the -f operator must be used.
     #  ($this.psobject.BaseObject.ToString("...") also crashes).
    "{0:N$numDecimalPlaces}" -f $this.psobject.BaseObject
  } -Force

}

[ThomasNieto]

To get the current behavior there should be a switch parameter on the format commands and a preference variable to enable/disable globally.

[vexx32]

I think that’s more likely to just be needlessly confusing, having one numeric type that behaves differently to the rest.

If this is going to change, all number types should behave similarly.