ConvertFrom-Json "[]" incorrectly returns $null instead of an empty array

Steps to reproduce & Expected results & Actual results

(ConvertFrom-Json "[]") -eq @()
#return False should return True

(ConvertFrom-Json "[]") -eq $null
# => returns True, should return False

Comment ConvertFrom-Json on Windows PSVersion = 5.1.18362.752 returns the correct value

Environment data

$PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.1.0-preview.6
PSEdition                      Core
GitCommitId                    7.1.0-preview.6
OS                             Darwin 19.6.0 Darwin Kernel Version 19.6.0: Thu Jun 18 20:49:00 PDT 2020; root:xnu-6153.14…
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[ElvenSpellmaker]

This is the most unexpected behaviour I think I’ve seen so far in Powershell…

When converting from an empty array you’d always expect an empty array… 🤔

[mklement0]

The ConvertFrom-Json default behavior was changed in v7 to exhibit the typical PowerShell behavior of enumerating arrays in the pipeline; thus, an empty array sends nothing through the pipeline (see #3424).

If you want to preserve a parsed-from-JSON array, use the -NoEnumerate switch:

# Output is, loosely speaking, $null
# (technically,  [System.Management.Automation.Internal.AutomationNull]::Value)
PS> (ConvertFrom-Json "[]") -is [array]  
False

# -NoEnumerate sends the (empty) array as-is, as whole to the pipeline.
PS> (ConvertFrom-Json "[]" -NoEnumerate) -is [array]
True