Can’t understand what is the easy way to add custom headers in Fable.PowerPack.Fetch about fable-powerpack HOT 7 CLOSED

PR is created: #20

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Here's an example, I hope it helps 😄

  GlobalFetch.fetch(
    RequestInfo.Url url,
    requestProps
      [ RequestProperties.Method HttpMethod.POST
        requestHeaders [ContentType "application/json"]
        RequestProperties.Body !^(toJson myObject) ])

fable-powerpack contains helpers for most common cases like this one. You can also check the tests.

from fable-powerpack.

I have no problems with predefined headers, but still not clear how to add custom headers.
Tests and code does not have examples.
This does not work:

        let headers =
            [   ContentType "application/x-www-form-urlencoded"
                "API-Key", Json.Encode.string apiKey
                "API-Sign", signature
            ]

from fable-powerpack.

@ed-ilyin Can you try something like that:

      let headers =  
            [   ContentType "application/x-www-form-urlencoded"
                !!("API-Key", Json.Encode.string apiKey)
                !!("API-Sign", signature)
            ]

!! comes from Fable.Core.JsInterop

I am not sure if this will work, but I saw people using this synthax for custom data attribute in Elmish and it's kind the same situation.
To explain, !! is equivalent to unbox(".....", "......") so it's simply make the compiler happy and Fable should convert the Key/Value into the desired object.

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Sorry @ed-ilyin, I misread the issue 😅 Thanks for the explanation, @MangelMaxime! That's right, you can use dynamic casting to fake a key-value pair when passing values to keyValueList. Another alternative is to add a union case with Erase attribute to the union type.

| [<Erase>] Custom of key:string * value:obj

Then you can do:

      let headers =  
            [   ContentType "application/x-www-form-urlencoded"
                Custom("API-Key", Json.Encode.string apiKey)
                // Same as !!("API-Key", Json.Encode.string apiKey) but typed
            ]

I just noticed the Erase attribute is not working in these cases in the current release, but I've fixed that for the next one. Also, please not the CaseRules (like LowerFirst letter) don't apply for custom headers.

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I like the idea with Custom case. Should I create PR?

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Yes, please :)

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