Runbook parameters do not handle complex types properly

Question

When passing parameters to Runbooks, neither PowerShell 5.1 nor PowerShell 7.1 handle parameter types appropriately. It appears that whatever strings I send in are passed through ConvertFrom-Json even if I want the parameter interpreted as a string.

According to the documentation, I should be able to pass JSON as a parameter that has type [object]. The documentation then uses ConvertFrom-Json to turn that into an object. But, when I pass JSON to my runbook, it is either already converted (and sometimes to an incorrect shape), or the JSON is corrupted and ConvertFrom-Json cannot parse it.

Using the following runbook:

param(  
 [string]$StringContainingText,  
 [string]$StringContainingJsonString,  
 [string]$StringContainingJsonArray,  
 [string]$StringContainingJsonObject,  
 [object]$Object,  
 [array]$Array  
)  
  
"StringContainingText: $($StringContainingText.GetType()) ~$StringContainingText~" | Write-Output  
"StringContainingJsonString: $($StringContainingJsonString.GetType()) ~$StringContainingJsonString~" | Write-Output  
"StringContainingJsonArray: $($StringContainingJsonArray.GetType()) ~$StringContainingJsonArray~" | Write-Output  
"StringContainingJsonObject: $($StringContainingJsonObject.GetType()) ~$StringContainingJsonObject~" | Write-Output  
  
"Object: $($Object.GetType()) ~$Object~" | Write-Output  
"Array: $($Array.GetType()) ~$Array~ Len: $($Array.Length) Len[0]: $($Array[0].Length)" | Write-Output  

And starting the runbook with this HTTP request:

{  
  "properties": {  
    "runbook": {  
      "name": "ParameterTest"  
    },  
    "parameters": {  
      "StringContainingText": "Hello, world",  
      "StringContainingJsonString": "\"Hello, world\"",  
      "StringContainingJsonArray": "[ \"one\", \"two\" ]",  
      "StringContainingJsonObject": "{ \"foo\": \"bar\" }",  
      "Object": "{ \"foo\": \"bar\" }",  
      "Array": "[ \"foo\", \"bar\", 123 ]"  
    },  
    "runOn": ""  
  }  
}  

A PowerShell 5.1 runbook produces the following output:

StringContainingText: string ~Hello, world~  
StringContainingJsonString: string ~Hello, world~  
StringContainingJsonArray: string ~one two~  
StringContainingJsonObject: string ~@{foo=bar}~  
Object: System.Management.Automation.PSCustomObject ~@{foo=bar}~  
Array: System.Object[] ~foo bar 123~ Len: 3 Len[0]: 3  

The PowerShell 5.1 result has the following problems:

• The string parameter StringContainingJsonString is missing the double-quotes at the beginning and end of the string
• The string parameter StringContainingJsonArray has is missing the square brackets and double-quotes
• The string parameter StringContainingJsonObject is completely mangled (it looks like it was converted to a PS hashtable then back to a string)

A PowerShell 7.1 runbook produces the following output:

StringContainingText: string ~Hello, world~  
StringContainingJsonString: string ~Hello, world~  
StringContainingJsonArray: string ~[ one, two ]~  
StringContainingJsonObject: string ~{ foo: bar }~  
Object: string ~{ foo: bar }~  
Array: System.Object[] ~[ foo, bar, 123 ]~ Len: 1 Len[0]: 17  

The PowerShell 7.1 result has the following problems:

• The string parameter StringContainingJsonString is missing the double-quotes at the beginning and end of the string
• The string parameter StringContainingJsonArray has is missing the square brackets and double-quotes
• The string parameter StringContainingJsonObject is completely mangled (it looks like it was converted to a PS hashtable then back to a string)
• The object parameter Object should be a hashtable, but instead is a string. The double quotes have been stripped so it is no longer valid JSON.
• The array parameter Array should contain 3 elements but instead contains 1 element which is the whole object mangled the same way StringContainingJsonArray is.