If the JSON contains duplicate keys with the same casing, then only the last key is used and the others are silently thrown away. The code in JsonObject.cs here actually caters for this case and would throw an error but it never gets to that stage because JsonConvert.DeserializeObject here does not throw when there are duplicate keys and simply decides to take the last one.

Steps to reproduce

'{ "key":"value1", "key":"value2" }' | ConvertFrom-Json

Expected behavior

Either a warning that duplicated keys were disregarded or an error stating that duplicate keys are not allowed unless e.g something like. a -Force switch is used. Given that this would be a breaking change, it will probably have to be a warning.

Actual behavior

Only the last key is used when there are duplicate keys

key
---
value2

Environment data

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      6.0.0-beta.8
PSEdition                      Core
GitCommitId                    v6.0.0-beta.8-20-g0d5a6fbd71c31043d0eda82f7b0e2d4fb0431322
OS                             Microsoft Windows 10.0.15063
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0