PowerShell doesn't recognize provided parameter - rest

Question

Operating System - Windows 10
Powershell version - 5.1.15063.1088
I'm using Windows PowerShell ISE (if that makes any sense). When running simple HTTP Post function
Function MyBeautifulFunction {
$myCredentials = Get-Credential
$body = #{
"query"="SELECT [System.Wheel],[System.SparkPlug],[System.EngineOil],[System.Headlight],[System.RadioButton] FROM JunkYard WHERE [System.Brand] = 'Ford' AND [System.Model] = 'GT' AND [System.Title] CONTAINS 'Rebuild'"
} | ConvertTo-Json
Invoke-RestMethod -Uri 'http://example.com//ford/parts/fuelpump/_apis/wit/wiql?api-version=2.0' `
-Method Post `
-Credential $myCredentials `
-Body $body `
-ContentType 'application/json'
}
MyBeautifulFunction
Editor's note: The Invoke-RestMethod call was originally spread across 2 lines without line continuation, which part of Adam's answer below discusses.
I'm getting following error message in PowerShell ISE console window:
"message":"The request indicated a Content-Type of \"application/x-www-form-urlencoded\" for method type \"POST\" which is not supported. Valid
content types for this method are: application/json, application/json-patch+json.
It's clearly visible that I'm passing 'application/json' in the parameter, but for some reason PowerShell still complains. Has anyone faced this error before? Should I report to Microsoft with it? Thanks for the advice...

Answer 1

Couple of things...
First, I call REST services all the time with a content type of application/json, and I don't have any problems. For example, the following works fine for me:
$url = 'https://jsonplaceholder.typicode.com/posts/1'
$response_from_webservice = Invoke-RestMethod -Uri $url -ContentType 'application/json' -Method 'Get'
jsonplaceholder... is a public service, available for testing. Feel free to run the snippet on your machine in-case you need a sanity check.
Second, this sample code you sent had this Accept parameter:
Invoke-RestMethod -Uri 'http://example.com//ford/parts/fuelpump/_apis/wit/wiql?api-version=2.0' -Method Post -Credential $myCredentials
-Body $body -ContentType 'application/json' -Accept 'application/json'
I don't believe I've seen that before. I am also running Windows 10 with Powershell v5.1.15063.1088. I've checked the docs. I checked out the commandlet's parameters. I didn't find it.
I share this to explain, I can't recreate your scenario with that call signature.
If you want to add an accept entry to the HTTP header, you'd have to do that directly:
$h = new-object 'system.collections.generic.dictionary[[string],[string]]'
$h.add('accept', 'application/json')
$r = Invoke-RestMethod -Uri '...' -ContentType 'application/json' -Method 'Post' -Headers $h
Third, it sort of looks like you're not specifying the content type in your snippet. The snippet has the Invoke-RestMethod on a seperate line from the body and contenttype parameters. Just to be clear, it's not wrapping. It looks like there is a line break there. That means that the second line -Body $body -ContentType 'application/json' -Accept 'application/json' is unassociated with the call that precedes it; the following is a copy and paste from your post:
Invoke-RestMethod -Uri 'http://example.com//ford/parts/fuelpump/_apis/wit/wiql?api-version=2.0' -Method Post -Credential $myCredentials
-Body $body -ContentType 'application/json' -Accept 'application/json'
If you want to put the parameters on a separate line, just use a backtick.
Invoke-RestMethod -Uri 'http://example.com//ford/parts/fuelpump/_apis/wit/wiql?api-version=2.0' `
-Method Post `
-Credential $myCredentials `
-Body $body `
-ContentType `
'application/json'
Now, if you don't specify the ContentType (as I'm suggesting) it will default to "application/x-www-form-urlencoded" on a post. According to Microsoft:
-ContentType
Specifies the content type of the web request.
If this parameter is omitted and the request method is POST,
Invoke-RestMethod sets the content type to
application/x-www-form-urlencoded. Otherwise, the content type is not
specified in the call.

Answer 2

You need to pass headers in to the headers argument
$headers = #{
"Content-Type" = "application/json",
"Accept" = "application/json"
}
Invoke-RestMethod -Uri 'http://example.com/123' -Method Post -Body $body -Headers $headers
See - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/invoke-restmethod