Azure Repos API Commits - GetChanges returning empty list - azure

Question

I have an Azure build pipeline with the following powershell task running on the agent to get the commits of my PR:
$id = $(System.PullRequest.PullRequestId)
$uri = "$(System.TeamFoundationCollectionUri)NPI/_apis/git/repositories/$(Build.Repository.ID)/pullRequests/$id/commits?api-version=5.1"
Write-Host "Getting all commits for PR" $id ":" $uri
$J = Invoke-WebRequest -URI $uri -Headers #{
Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN"
} | ConvertFrom-Json
And then loop through the reply like this:
foreach ($c in $J.value)
{
$id = $c.commitId
$uri = "$(System.TeamFoundationCollectionUri)NPI/_apis/git/repositories/$(Build.Repository.ID)/commits/$id/changes?api-version=5.1"
Write-Host "Getting details for commit" $id ":" $uri
$J = Invoke-WebRequest -URI $uri -Headers #{
Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN"
} | ConvertFrom-Json
Write-Host $J
}
The log file of the Azure task contains this:
Getting all commits for PR 1026 : https://dev.azure.com/xxx/xxx/_apis/git/repositories/xxx/pullRequests/1026/commits?api-version=5.1
Getting details for commit xxx : https://dev.azure.com/xxx/xxx/_apis/git/repositories/xxx/commits/xxx/changes?api-version=5.1
#{changeCounts=; changes=System.Object[]}
As you can see, there are no changes listed. However, if I click on the logged url for getting the commit details, I get a non-empty list. What's going on here?

Answer 1

Oops, turns out it does actually work but the Write-Host output is broken.
This runs fine:
foreach ($cc in $J.changes)
{
Write-Host $cc.item.path
}

Answer 2

You need a variable to store it before convert to json. This is work correctly to me.
"$($env:SYSTEM_TEAMFOUNDATIONCOLLECTIONURI)$env:SYSTEM_TEAMPROJECTID/_apis/git/repositories/$($pipeline.repository.id)/commits/$(Build.BuildId)/changes?api-version=5.0"
Write-Host $commitUrl
$rsCommit = Invoke-RestMethod -Uri $commitUrl -Headers #{
Authorization = "Bearer $env:SYSTEM_ACCESSTOKEN"}
Write-Host "CommitInfo = $($rsCommit | ConvertTo-Json -Depth 100)"