Idempotency problem when formatting quotations

[sergey-tihon]

Issue created from fantomas-online

Original code

let action =
    <@
        let msg = %httpRequestMessageWithPayload
        RuntimeHelpers.fillHeaders msg %heads
        async {
            let! response = (%this).HttpClient.SendAsync(msg) |> Async.AwaitTask
            return response.EnsureSuccessStatusCode().Content
        }
    @>

Formatted code

let action =
    <@ let msg = %httpRequestMessageWithPayload
    RuntimeHelpers.fillHeaders msg %heads

    async {
        let! response =
            (%this).HttpClient.SendAsync(msg)
            |> Async.AwaitTask

        return response.EnsureSuccessStatusCode().Content
    } @>

Reformatted code

let action =
    <@ let msg = %httpRequestMessageWithPayload

       RuntimeHelpers.fillHeaders
           msg
           %heads

           async {
           let! response =
               (%this).HttpClient.SendAsync(msg)
               |> Async.AwaitTask

           return response.EnsureSuccessStatusCode().Content
       } @>

Problem description

Fantomas was not able to produce the same code after reformatting the result.

Extra information

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

Options

Fantomas master branch at 2022-04-12T06:26:27Z - 7b35c89

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, thank you for reporting this!

I believe we currently, don't have a good way of dealing with multiline quotation expressions.
We should extend

fantomas/src/Fantomas/CodePrinter.fs

Lines 1356 to 1361 in 04d176a

	let e =
	match e2 with
	| DotGetApp _ -> atCurrentColumnIndent (genExpr astContext e2)
	| _ -> genExpr astContext e2
	ifElse isRaw (!- "<@@ " +> e -- " @@>") (!- "<@ " +> e -- " @>")

to something like:

    let e = expressionFitsOnRestOfLine (genExpr astContext e2) (indent +> sepNln +> genExpr astContext e2 +> unindent +> sepNln)
    ifElse isRaw (!- "<@@" +> sepSpace +> e => sepSpace +> !- " @@>") (!- "<@" +> sepSpace +> e +> sepSpace +>  !- "@>")

(Didn't test this code)

This will slightly change the outcome of #2154
But as I reported this one myself, it should be fine to change it.

Are you interested in submitting a PR for this one?

[sergey-tihon]

Are you interested in submitting a PR for this one?

Sorry, no, at least not now.

This bug is not critical at all, I just tried Fantomas on TypeProvider project and discovered this issues.
It may leave for a while in Open state if it is not critical for others