PowerShell-PowerShell/src/System.Management.Automation/DscSupport/JsonDeserializer.cs

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Management.Automation;
using System.Management.Automation.Runspaces;

namespace Microsoft.PowerShell.DesiredStateConfiguration.Internal.CrossPlatform
{
    internal class JsonDeserializer
    {
        #region Constructors

        /// <summary>
        /// Instantiates a default deserializer.
        /// </summary>
        /// <returns>Default deserializer.</returns>
        public static JsonDeserializer Create()
        {
            return new JsonDeserializer();
        }

        #endregion Constructors

        #region Methods

        /// <summary>
        /// Returns schema of Cim classes from specified json file.
        /// </summary>
        /// <param name="json">Json text to deserialize.</param>
        /// <param name="useNewRunspace">If a new runspace should be used.</param>
        /// <returns>Deserialized PSObjects.</returns>
        public IEnumerable<PSObject> DeserializeClasses(string json, bool useNewRunspace = false)
        {
            if (string.IsNullOrEmpty(json))
            {
                throw new ArgumentNullException(nameof(json));
            }

            System.Management.Automation.PowerShell powerShell = null;

            if (useNewRunspace)
            {
                // currently using RunspaceMode.NewRunspace will reset PSModulePath env var for the entire process
                // this is something we want to avoid in DSC GuestConfigAgent scenario, so we use following workaround
                var s_iss = InitialSessionState.CreateDefault();
                s_iss.EnvironmentVariables.Add(
                    new SessionStateVariableEntry(
                        "PSModulePath",
                        Environment.GetEnvironmentVariable("PSModulePath"),
                        description: null));
                powerShell = System.Management.Automation.PowerShell.Create(s_iss);
            }
            else
            {
                powerShell = System.Management.Automation.PowerShell.Create(RunspaceMode.CurrentRunspace);
            }

            using (powerShell)
            {
                return powerShell.AddCommand("Microsoft.PowerShell.Utility\\ConvertFrom-Json")
                    .AddParameter("InputObject", json)
                    .AddParameter("Depth", 100) // maximum supported by cmdlet
                    .Invoke();
            }
        }

        #endregion Methods
    }
}