Fable's JsInterop ? dynamic access operator causes formatting error

[joprice]

Issue created from fantomas-online

Code

Jest.expect(json)?oMatchSnapshot ()

Error

System.Exception: cannot determine if Expr AppLongIdentAndSingleParenArg
  Fantomas.Core.SyntaxOak+ExprAppLongIdentAndSingleParenArgNode is uppercase or lowercase
   at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1448.Invoke(String message)
   at Fantomas.Core.CodePrinter.sepSpaceBeforeParenInFuncInvocation(Expr functionExpr, Expr argExpr, Context ctx) in /_//src/Fantomas.Core/CodePrinter.fs:line 2549
   at Fantomas.Core.CodePrinter.genExpr@1036-197.Invoke(Context ctx)
   at Fantomas.Core.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /_//src/Fantomas.Core/Context.fs:line 430
   at Fantomas.Core.Context.shortExpressionWithFallback(FSharpFunc`2 shortExpression, FSharpFunc`2 fallbackExpression, Int32 maxWidth, FSharpOption`1 startColumn, Context ctx) in /_//src/Fantomas.Core/Context.fs:line 616
   at Fantomas.Core.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /_//src/Fantomas.Core/Context.fs:line 430
   at Fantomas.Core.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /_//src/Fantomas.Core/Context.fs:line 430
   at Fantomas.Core.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /_//src/Fantomas.Core/Context.fs:line 463
   at Fantomas.Core.CodePrinter.genFile@4066-4.Invoke(Context ctx)
   at Fantomas.Core.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /_//src/Fantomas.Core/Context.fs:line 430
   at Fantomas.Core.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /_//src/Fantomas.Core/Context.fs:line 430
   at Fantomas.Core.CodeFormatterImpl.formatAST(ParsedInput ast, FSharpOption`1 sourceText, FormatConfig config, FSharpOption`1 cursor) in /_//src/Fantomas.Core/CodeFormatterImpl.fs:line 74
   at Fantomas.Core.CodeFormatterImpl.formatDocument@89-3.Invoke(Unit unitVar) in /_//src/Fantomas.Core/CodeFormatterImpl.fs:line 89
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvoke[T,TResult](AsyncActivation`1 ctxt, TResult result1, FSharpFunc`2 part2) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 508
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 112

Problem description

When using the ? operator on the result of a tupled function call, a parse error is hit. A workaround is to call the first function without parens: (Jest.expect json)?oMatchSnapshot ()

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.
• I would like a release if this problem is solved.

Options

Fantomas main branch at 11/04/2024

Default Fantomas configuration

_{Did you know that you can ignore files when formatting by using a .fantomasignore file?
PS: It's unlikely that someone else will solve your specific issue, as it's something that you have a personal stake in.}

[nojaf]

Hello,

Thanks for reporting this problem!

You would need to extend

fantomas/src/Fantomas.Core/CodePrinter.fs

Lines 44 to 63 in b7dca79

	match expr with
	| Expr.Ident ident -> upperOrLower ident.Text
	| Expr.OptVar node -> lastFragmentInList node.Identifier
	| Expr.Chain node ->
	match List.tryLast node.Links with
	| None
	| Some(ChainLink.Dot _) -> LowercaseExpr
	| Some(ChainLink.Identifier e)
	| Some(ChainLink.Expr e) -> (|UppercaseExpr|LowercaseExpr|) e
	| Some(ChainLink.AppParen appParen) -> (|UppercaseExpr|LowercaseExpr|) appParen.FunctionName
	| Some(ChainLink.AppUnit appUnit) -> (|UppercaseExpr|LowercaseExpr|) appUnit.FunctionName
	// Questionable
	| Some(ChainLink.IndexExpr _) -> LowercaseExpr
	| Expr.DotIndexedGet node -> (|UppercaseExpr|LowercaseExpr|) node.ObjectExpr
	| Expr.TypeApp node -> (|UppercaseExpr|LowercaseExpr|) node.Identifier
	| Expr.Dynamic node -> (|UppercaseExpr|LowercaseExpr|) node.FuncExpr
	| Expr.AppSingleParenArg node -> (|UppercaseExpr|LowercaseExpr|) node.FunctionExpr
	| Expr.Paren node -> (|UppercaseExpr|LowercaseExpr|) node.Expr
	| Expr.App node -> (|UppercaseExpr|LowercaseExpr|) node.FunctionExpr
	| _ -> failwithf "cannot determine if Expr %A is uppercase or lowercase" expr

with Expr.AppLongIdentAndSingleParenArg where you want to check the FunctionName I think.

Would you be interested in sending a PR for this?