Updating an imported access token doesn't work in PowerShell 7

[ghvanderweg]

While writing this I kept digging deeper to find a solution, and I think I've got it, so I'd like to explain my thought process :)

I upgraded to PowerShell 7 today, and Update-GraphOauthAccessToken broke. After using Export-GraphOauthAccessToken and Import-GraphOauthAccessToken to export & import an access token, if you then try to update the token with Update-GraphOauthAccessToken, it fails with the error:

Update-GraphOauthAccessToken: Failed to refresh token: The format of value '' is invalid.
In PowerShell 5.1, this works fine.

I tracked the error down to the WebSession header in the Invoke-Webrequest call (line 102 of Update-GraphOauthAccessToken.ps1). Omitting that header fixed the issue. But since the header works fine in PowerShell 5.1, I looked into it a bit further.

I compared the Session property of an original access token and an imported token, and it seems the Session property loses the content of the UserAgent subproperty on serializing/deserializing.

Manually adding the user agent back fixed the issue. Next, I checked the XML that's saved to disk, and the user agent is present there, so the issue has to be with Import-GraphOauthAccessToken.ps1. I think I located a bug at line 110, which reads

$Session.UserAgent = $Application.UserAgent

If I'm not mistaken, this should be

$Session.UserAgent = $InObject.Session.UserAgent

This will properly deserialize the UserAgent property and keep Invoke-WebRequest happy :)