Required backslash removed in string interpolation

[suside]

Issue created from fantomas-online

Code

$"INSERT INTO \"{tableName}\" {colNames} VALUES {values}"

Result

$"INSERT INTO "{tableName}" {colNames} VALUES {values}"

Problem description

Interestingly, formating this does not remove \:

$"INSERT INTO \"{tableName}\" {colNames} VALUES"

so it's like the third variable is causing the error?

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 12/26/2020 15:00:23 - 76fa31e

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 @suside, thank you for reporting this issue.
This looks like a Trivia issue somewhere around

fantomas/src/Fantomas/CodePrinter.fs

Line 2512 in d5f4d9f

let stringsFromTrivia =

Would you be interested in submitting a PR?

[suside]

Hi @nojaf
I took a look but unfortunately I don't know what's wrong there 😕

Failing test case:

[<Test>]
let ``backslash in interpolation, issue 1344`` () =
    formatSourceString
        false """
$"\"{bar}\" {1} {2}"
"""
        config
    |> prepend newline
    |> should
        equal """
$"\"{bar}\" {1} {2}"
"""

[nojaf]

I believe the active pattern

fantomas/src/Fantomas/TokenParser.fs

Lines 514 to 518 in d5f4d9f

	let private (|InterpStringEndToken|_|) token =
	if token.TokenInfo.TokenName = "INTERP_STRING_END" then
	Some token
	else
	None

Needs to be changed to:

let private (|InterpStringEndOrPartToken|_|) token =
    if token.TokenInfo.TokenName = "INTERP_STRING_END"
       || token.TokenInfo.TokenName = "INTERP_STRING_PART" then
        Some token
    else
        None

In order to capture all interpolated strings as trivia.