Wrong change of comment's position

[knocte]

Issue created from fantomas-online

Code

exception LoadedSourceNotFoundIgnoring of (*filename*) string * range

Result

exception LoadedSourceNotFoundIgnoring of string * range (*filename*)

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 4.6 branch at 11/07/2021 14:33:13 - a4d21fe

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 issue.
The trivia is assigned to SynUnionCase_ while the first SynField_ might be the better candidate.
Are you interested in submitting a PR?

[ribeirotomas1904]

I saw that we are calling genField inside genUnionCase when the fields are not empty on CodePrinter.fs, but I can't find why it's not generating the trivia for the field

[ribeirotomas1904]

We also have other similar cases happening here

[nojaf]

The trivia is not assigned to SynField_ but to SynUnionCase_, the main problem is that the Ident of the exception (LoadedSourceNotFoundIgnoring ) is not picked up in ASTTransformer:

fantomas/src/Fantomas/AstTransformer.fs

Lines 1113 to 1118 in fe22e31

	and visitSynUnionCase (uc: SynUnionCase) : TriviaNodeAssigner list =
	match uc with
	| SynUnionCase (attrs, _, uct, _, _, range) ->
	[ yield mkNode SynUnionCase_ range
	yield! visitSynUnionCaseType uct
	yield! (visitSynAttributeLists attrs) ]

should be something like:

    and visitSynUnionCase (uc: SynUnionCase) : TriviaNodeAssigner list =
        match uc with
        | SynUnionCase (attrs, ident, uct, _, _, range) ->
            [ yield mkNode SynUnionCase_ range
              yield visitIdent ident
              yield! visitSynUnionCaseType uct
              yield! (visitSynAttributeLists attrs) ]

that will lead to the comment being assigned to the right node.

However, for this to be processed correctly in CodePrinter, you would need to extend the active pattern in SourceParser:

fantomas/src/Fantomas/SourceParser.fs

Lines 31 to 44 in 18eda76

	let (|Ident|) (s: Ident) =
	let ident = s.idText
	match ident with
	| "`global`" -> "global"
	| "not" -> "not"
	| "params" -> "``params``"
	| "parallel" -> "``parallel``"
	| "mod" -> "``mod``"
	| _ ->
	if IsActivePatternName ident then
	sprintf "(%s)" (DecompileOpName ident)
	else
	AddBackticksToIdentifierIfNeeded ident

to include the range and print the trivia in CodePrinter.

This is used in a lot of places so a helper function in CodePrinter might be a good idea.

[nojaf]

We also have other similar cases happening here

Similar kind of bug, different solution, please open a new issue.