How do I expand variables in a JSON string in Powershell? - json

Question

Goal: Get information from one API request, store those into variables and pass into a new API request to make a JIRA issue.
Env:
Powershell 5.1
Windows 10
Problem: I have no issues with the first two steps in the goal. But I'm not sure how to properly construct the last step.
$summary = 'summary'
$desc = 'desc'
$Body = '{
"fields": {
"project": {"key": "ABC"},
"summary": "${summary}",
"description": ${desc},
"issuetype": {"name": "Story"},
"assignee" : {"name":"bob"}
}
}'
Actual Results: The variables are interpreted literally.
Expected Results: The variables should be expanded in the string.
What I've tried:
I am aware the variable is currently wrapped in single quotes. But using double quotes is not ideal either. There are too many other double quotes to escape. What if I have a massive JSON body? I have to manually put a backtick for each double quote inside. What is a more elegant solution?
Referred to https://adamtheautomator.com/powershell-escape-double-quotes/#Using_PowerShell_to_Escape_Double_Quotes
Many thanks in advance.

Answer 1

There are more ways than one to do this, depending on how large the body json needs to be, you can choose to do that using
Method 1, create a double-quoted Here-String (no need to escape the other double-quotes):
$summary = 'summary'
$desc = 'desc'
$Body = #"
{
"fields": {
"project": {"key": "ABC"},
"summary": "$summary",
"description": "$desc",
"issuetype": {"name": "Story"},
"assignee" : {"name":"bob"}
}
}
"#
Method 2: create the body as template with self-defined placeholders to be used multiple times if needed
$summary = 'summary'
$desc = 'desc'
$template = #'
{
"fields": {
"project": {"key": "ABC"},
"summary": "##SUMMARY##",
"description": "##DESCRIPTION##",
"issuetype": {"name": "Story"},
"assignee" : {"name":"bob"}
}
}
'#
$Body = $template -replace '##SUMMARY##', $summary -replace '##DESCRIPTION##', $desc
Method 3: create numbered placeholders for use with the -f Format operator.
This has the disadvantage that ALL other existing curly brackets { and } have to be doubled..
$summary = 'summary'
$desc = 'desc'
$template = #'
{{
"fields": {{
"project": {{"key": "ABC"}},
"summary": "{0}",
"description": "{1}",
"issuetype": {{"name": "Story"}},
"assignee" : {{"name":"bob"}}
}}
}}
'#
$Body = $template -f $summary, $desc
Method 4, create the body as nested PsCustomObject and convert that to Json
$summary = 'summary'
$desc = 'desc'
$Body = [PsCustomObject]#{
fields = [PsCustomObject]#{
project = [PsCustomObject]#{key = 'ABC'}
summary = $summary
description = $desc
issuetype = [PsCustomObject]#{name = 'Story'}
assignee = [PsCustomObject]#{name = 'bob'}
}
} | ConvertTo-Json -Depth 3 # you can also set this way higher to be on the safe side

Answer 2

You can build a PsObject and convert it to Json format with ConvertTo-Json.
Something like this
$firstname = "myFirstName"
$lastname = "myLastName"
$properties = [ordered]#{
firstname = $firstname
lastname = $lastname
}
$obj = New-Object psobject -Property $properties;
$body = convertto-json $obj
PS >$body
{
"firstname": "myFirstName",
"lastname": "myLastName"
}