string interpolation with multi-line string causes literal part to change

[johlrich]

Issue created from fantomas-online

Code

module ApiPolicy

open Pulumi

let create (discoveryUrl: Input<string>) (aud: Input<string>) (backendId: Input<string>) =
  Output.Format(
    $"""<policies>
  <inbound>
    <validate-jwt header-name="Authorization" failed-validation-httpcode="401" failed-validation-error-message="Unauthorized. Access token is missing or invalid." require-expiration-time="true" require-scheme="Bearer" require-signed-tokens="true">
      <openid-config url="{discoveryUrl}" />
      <required-claims>
        <claim name="aud">
          <value>{aud}</value>
        </claim>
      </required-claims>
    </validate-jwt>
    <set-backend-service backend-id="{backendId}" />
  </inbound>
  <backend>
    <base />
  </backend>
  <outbound>
    <base />
  </outbound>
  <on-error>
    <base />
  </on-error>
</policies>"""
  )

Result

module ApiPolicy

open Pulumi

let create (discoveryUrl: Input<string>) (aud: Input<string>) (backendId: Input<string>) =
    Output.Format(
        $"""<policies>
  <inbound>
    <validate-jwt header-name="Authorization" failed-validation-httpcode="401" failed-validation-error-message="Unauthorized. Access token is missing or invalid." require-expiration-time="true" require-scheme="Bearer" require-signed-tokens="true">
      <openid-config url="{discoveryUrl}" />      <required-claims>        <claim name="aud">          <value>{aud}</value>        </claim>      </required-claims>    </validate-jwt>    <set-backend-service backend-id="{
                                                                                                                                                                                                                                backendId
        }" />  </inbound>  <backend>    <base />  </backend>  <outbound>    <base />  </outbound>  <on-error>    <base />  </on-error></policies>"""
    )

Problem description

The combination of a string interpolation and a multi-line string causes fantomas to both add whitespace to the { } expression as well as change the formatting of the string itself after the first interpolation expression found.

Extra information

• The formatted result breaks by code.
• The formatted result gives compiler warnings.
• I or my company would be willing to help fix this.

Options

Fantomas Master at 02/12/2021 20:07:06 - e016b1c

Default Fantomas configuration

_{Did you know that you can ignore files when formatting from fantomas-tool or the FAKE targets by using a .fantomasignore file?}

[nojaf]

Hello Jonathan, thank you for reporting this issue.
I believe the issue here is that we are not taking newlines found in the Tokens into account in

fantomas/src/Fantomas/TokenParser.fs

Lines 734 to 737 in e016b1c

	let stringContent =
	[ yield! (List.map (fun t -> t.Content) stringTokens)
	yield interpStringEnd.Content ]
	|> String.concat String.Empty

Would you be interested to submit a PR for this?

[johlrich]

I would like to try, yes. Thanks for suggesting a place to start.

[nojaf]

Great to hear, please read our Contribution guidelines first as they contain some other useful tips.
You can also ask some questions via a draft PR if you need any help.
Good luck!