Verify and fix compatibility with different PowerShell Core versions

[lupino3]

As discovered in #35, it looks like loading NJsonSchema will fail if it conflicts with the version shipped with PowerShell.

We should verify what versions of PowerShell Core we are currently compatible with, and ideally work around any limitations.

[lupino3]

The current code works with PowerShell >= 7.2.0-rc1 (tested 7.2.0-rc1, 7.2.0, 7.2.2, 7.2.5).
Previous versions fail with the following error

Could not load file or assembly 'Newtonsoft.Json, Version=13.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'.

[lupino3]

Previous versions break in different ways:

From 6.1.0 on, they break with

Could not load file or assembly 'Newtonsoft.Json, Version=13.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'.

Between 6 and 6.1.0, they break with

System.IO.FileNotFoundException: Could not load file or assembly 'System.Management.Automation, Version=6.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'. The system cannot find the file specified.

6.1.0 is the version when the Test-Json cmdlet was introduced. That cmdlet supports validating a JSON file against a schema.

We might be able to fix the incompatibility with Newtonsoft.Json by using Test-Json in all versions above 6.1.0.

Not sure if it's possible to easily fix compatibility with PowerShell 6 - 6.1.0, but considering that PowerShell 6.x stopped being supported in September 2020 it may be not be worth fixing it.

[lupino3]

Note that the error for PowerShell 6 before 6.1.0 is a Pester error, not an error from this library.

I tried manually importing Newtonsoft.Json, and got the very same error:

PS /app> Write-Host $PSVersionTable.PSVersion
6.0.4
PS /app> Add-Type -Path ./External/newtonsoft.json/13.0.1/lib/netstandard1.0/Newtonsoft.Json.dll
Add-Type : Could not load file or assembly 'Newtonsoft.Json, Version=13.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed'.
At line:1 char:1
+ Add-Type -Path ./External/newtonsoft.json/13.0.1/lib/netstandard1.0/N ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Add-Type], FileLoadException
+ FullyQualifiedErrorId : System.IO.FileLoadException,Microsoft.PowerShell.Commands.AddTypeCommand

I don't think there is an easy way to be compatible with PowerShell 6.0.x, so I'll close this issue and open a new one to track future work to improve this compatibility.

[lupino3]

Reopening as I actually found and fixed the issue 😮‍💨

Now Pester is complaining about running under that version of Powershell.

[lupino3]

Note that #39 fixed compatibility with PowerShell Core >= 6.1.0.