Powershell variable not displaying nested object - powershell

Question

I am sending a GET request that returns an object. Using postman, I get:
{
"changedInstance": {
"change": "Created",
"instanceAfterChange": {
"instanceId": "123",
"schemaName": "RBAC",
"className": "PermissionCategory",
"properties": {
"Name": "IModel Schema Management Service",
"TypeId": 2,
"TypeName": "Service Access and Permissions"
}
}
}}
But when I send a request through Powershell, I get the response:
#{change=Created; instanceAfterChange=}
The request I have made:
$Response = Invoke-RestMethod -Uri $base_url/v2.4/Repositories/BentleyCONNECT--Main/RBAC/PermissionCategory -Method Post -Headers #{'Authorization' = 'Bearer ' + $global:token} -Body $postParams -ContentType "application/json"
I have checked all the header values and the body, no values are missing.
The property 'instanceAfterChange' is empty, however when I monitor this same request in fiddler, it shows the correct response. My question is, why is Powershell displaying it as empty even though when it is not.

Answer 1

ConvertFrom-Json constructs a [pscustomobject] instance from your JSON input, and what you're seeing (#{change=Created; instanceAfterChange=}) is the default display formatting for the instance's .changedInstance property value.
Due to a bug as of PowerShell 7.0, the default display formatting makes it appear as if property instanceAfterChange is empty, but it actually isn't.
Specifically, the bug is that calling .ToString() on [pscustomobject] instances unexpectedly yields the empty string - see this GitHub issue.
The hashtable-like display representation of [pscustomobject]s as property values - as shown in your question and explained in this answer - involves .ToString() calls on nested [pscustomobject] instances, which is why the bug surfaces.
Therefore, you shouldn't have a problem accessing the nested [pscustomobject]s' properties, e.g., $convertedFromJson.changedInstance.instanceAfterChange.schemaName should yield RBAC.
An easy way to verify that the data is there is to convert back to JSON (ConvertTo-Json) or to visualize the structure via Format-Custom.
A simplified example:
$convertedFromJson = '{
"changedInstance": {
"instanceAfterChange": {
"instanceId": "123",
"schemaName": "RBAC"
}
}
}
' | ConvertFrom-Json
# Output as-is: the bug makes .changedInstance appear empty.
$convertedFromJson
'---'
# Access a nested property - this works.
$convertedFromJson.changedInstance.instanceAfterChange.schemaName
'---'
# Visualize the structure of the nested object.
$convertedFromJson | Format-Custom
The above yields:
changedInstance
---------------
#{instanceAfterChange=} # DISPLAY BUG: .instanceAfterChange appears empty.
---
RBAC # OK: accessing a property of .instanceAfterChange works.
---
# Visualization of the nested object's structure via Format-Custom
class PSCustomObject
{
changedInstance =
class PSCustomObject
{
instanceAfterChange =
class PSCustomObject
{
instanceId = 123
schemaName = RBAC
}
}
}