scalafmt breaks for/yield blocks using significant indentation

[zainab-ali]

Formatted for/yield blocks with long variable names fail to compile. scalafmt inserts a newline, which breaks code using significant indentation.

Configuration

version = 3.8.3
runner.dialect = scala3

Command-line parameters

When I run scalafmt via CLI like this: scalafmt reproduction.scala

Steps

Given code like this:

val loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
    : Option[Int] = Some(1)

val expression = for (
  x <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu;
  y <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
) yield x + y

Problem

Scalafmt formats code like this:

val loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
    : Option[Int] = Some(1)

val expression = for (
  x <-
    loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu;
  y <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
) yield x + y

This fails to compile with:

λ> scala-cli compile reproduction.scala
Compiling project (Scala 3.2.2, JVM)
[error] ./reproduction.scala:7:5
[error] expression expected but <- found
[error]   y <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
[error]     ^^
[error] ./reproduction.scala:6:5
[error] value y is not a member of Option[Int].
[error] Note that `y` is treated as an infix operator in Scala 3.
[error] If you do not want that, insert a `;` or empty line in front
[error] or drop any spaces behind the operator.

Expectation

I would like the formatted output to compile.

val loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
    : Option[Int] = Some(1)

val expression = for (
  x <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu;
  y <- loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
) yield x + y

Workaround

The indentation is not introduced if maxColumns is increased, e.g. maxColumns=100. It is not introduced if the variable name is shorter in length.

[kitbellew]

my guess is, if you're using scala3 (with optional braces), another workaround is:

val expression = for
  x <-
    loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
  y <-
    loremipsumdolorsitametconsecteturadipiscingelitseddoeiusmodtemporincididu
yield x + y

[kitbellew]

@zainab-ali can you please point where on this page it explains why your code doesn't compile: https://docs.scala-lang.org/scala3/reference/syntax.html

all i can see is that there's no special treatment of parens vs braces vs opt-braces in

ForExpr           ::=  ‘for’ ‘(’ Enumerators0 ‘)’ {nl} [‘do‘ | ‘yield’] Expr
                    |  ‘for’ ‘{’ Enumerators0 ‘}’ {nl} [‘do‘ | ‘yield’] Expr
                    |  ‘for’     Enumerators0          (‘do‘ | ‘yield’) Expr

@tgodzik who is the expert on scala3 syntax who may have authored the page above?