This fixes parsing

puts "foo #{"bar"
}"

to produce foo bar in stdout, however that example still can't be formatted.

If we can come to a quick consensus on how this should be formatted we should include that change in this PR, if it gets to be a lengthy discussion we can fix it later.

To me the above example should format to

puts "foo #{"bar"}"

but i'm not sure what this (and similar) should format to:

puts "foo #{
  "bar"
}"

Also "Correctly parse ..." is correct English, instead of "Correct to parse ..."

I am not sure if the formatter should remove newlines even in the first case.

@straight-shoota Even if the first case's newline is intended, we can use backslash + newline escape in this case (and I think we should use it.)

puts "foo #{"bar"}\
"

@RX14 I can't understand the difference between "to do" and "doing"...

I considered some ideas to format string interpolation with newline:

Original source code:

"foo #{
  bar = 1
} baz"

Idea 1: keep

"foo #{
  bar = 1
} baz"

Idea 2: align with delimiter

"foo #{
       bar = 1
     } baz"

Idea 3: remove newline and indent

"foo #{bar = 1} baz"

I don't know which is the best and I can't decide it. I guess, the preference of idea 1 is unstable (and I don't like it). Idea 2 is the best if it follows no string, so:

"foo #{
       bar = 1
     }"

this indentation looks like foo = begin ... end pattern, so it is good enough. However when it follows any string, I think it is ugly. Idea 3, crystal tool format disallow newline inside string interpolation in other words, is good for me, because I think we shouldn't write too complex expression to need newline inside string interpolation, but I don't know this is general opinion.

I think the rule should be that if there's a newline after #{ we do idea 1 (indent 1 indent then format normally), otherwise keep it as-is. That means that the original example formats to

puts "foo #{"bar"}"

but

puts "foo #{
  "bar"
}"

formats as-is.

Ok. I implemented formatting string interpolation in this way.

Thank you @makenowjust!