record mutation: first field after with should be placed in a new line

[yatli]

I'm integrating fantomas into coc-fsharp with API FormatDocumentAsync.
I'm using 3.0-beta002 nuget package.

Problem example:

                return { 
                    capabilities = 
                        { defaultServerCapabilities with 
                            hoverProvider = true
                            completionProvider = Some({resolveProvider=true; triggerCharacters=['.']})
                            signatureHelpProvider = Some({triggerCharacters=['('; ',']})
                            documentSymbolProvider = true
                            codeActionProvider = true
                            codeLensProvider = Some({resolveProvider=true})
                            workspaceSymbolProvider = true
                            definitionProvider = true
                            referencesProvider = true
                            renameProvider = true
                            documentFormattingProvider = true
                            documentRangeFormattingProvider = true
                            textDocumentSync = 
                                { defaultTextDocumentSyncOptions with 
                                    openClose = true 
                                    save = Some({ includeText = false })
                                    change = TextDocumentSyncKind.Incremental 
                                } 
                        }
                }

becomes:

                return { capabilities =
                             { defaultServerCapabilities with hoverProvider = true
                               completionProvider =
                                   Some({ resolveProvider = true
                                          triggerCharacters = [ '.' ] })
                               signatureHelpProvider = Some({ triggerCharacters = [ '('; ',' ] })
                               documentSymbolProvider = true
                               codeActionProvider = true
                               codeLensProvider = Some({ resolveProvider = true })
                               workspaceSymbolProvider = true
                               definitionProvider = true
                               referencesProvider = true
                               renameProvider = true
                               documentFormattingProvider = true
                               documentRangeFormattingProvider = true
                               textDocumentSync =
                                   { defaultTextDocumentSyncOptions with openClose = true
                                     save = Some({ includeText = false })
                                     change = TextDocumentSyncKind.Incremental } } }
            }

online fantomas code

Note, this problem does not repro with all record mutations -- not sure about the condition, but I tried a few simpler cases and it works as expected -- this is exactly the repro snippet, extracted from the full source file given in the link above.

[yatli]

I've also tried to first typecheck with my language server, and send the AST to Fantomas -- the formatting result is mostly correct (see #456), but the comments are gone.

[jindraivanek]

I've also tried to first typecheck with my language server, and send the AST to Fantomas -- the formatting result is mostly correct (see #456), but the comments are gone.

Comments are not included in AST.

[yatli]

Comments are not included in AST.

I know.

I think the first part is more interesting -- using AST does not repro the problem.

[jindraivanek]

Oh, okay, I misinterpreted it.

That means problem is probably in comments.

This issue is definitely elusive, I tried to find smaller repro but without success (for example whole class Server is formatted correctly).

[jindraivanek]

I was able to find minimized repro.

[nojaf]

Ok, so fix could be to auto add a newline after the with keyword if there are multiple members?

[yatli]

@nojaf ideally yes. I haven’t dig into fantomas codebase yet — just wondering: why does it behave correctly in some conditions?

@jindraivanek did you find patterns? That minimal repro definitely helps to simplify things. :)

[yatli]

In the minimal repro, if we remove the first line (let x = .....), then the record formats correctly.
Semantically it seems irrelevant...?
Even more interesting: changing the first line to:
let x = 1 // no repro
let x = foo.bar(2) //no repro
let x = foo(1).bar(2) // repro!

[yatli]

Turning on strict mode mutes the repro — this echos the AST formatting approach.

[jindraivanek]

@yatli Yes, also
foo(x).bar() //no repro
foo(1).bar //no repro

[yatli]

let x = Foo(1).Bar 1 //repro
let x = (Foo 1).Bar 1 // no repro

[yatli]

ok, the reason "it doesn't repro on simpler cases":

let _ = 
    let x = Foo(1).Bar()
    x

let F x = x

type T = A | B | C of int

let r =
    { s with
        x = 1
        y = 2 }
// repro

It infects following lines

[yatli]

...and this:

let r =
    { s with
        x = 1
        y = 2 }

let x = (fun () -> Foo(1).Bar())

let r =
    { s with
        x = 1
        y = 2 }

===>

let r =
    { s with
          x = 1
          y = 2 }

let x = (fun () -> Foo(1).Bar())

let r =
    { s with x = 1
      y = 2 }

[yatli]

It turns on some kind of switch?

[jindraivanek]

I found the bug, it was indeed caused by incorrectly set switch here:

fantomas/src/Fantomas/Context.fs

Lines 402 to 406 in 7d5d3f1

	let internal noNln f (ctx : Context) : Context =
	ctx.BreakLines <- false
	let res = f ctx
	ctx.BreakLines <- true
	res

Will fix soon.