This with break-string-literal=newlines-and-wrap (or newlines):
let _ = "abc@,def\n\nghi"
Diff of the AST:
pattern (_none_[0,0+-1]..[0,0+-1]) ghost
Ppat_any
expression (_none_[0,0+-1]..[0,0+-1]) ghost
- Pexp_constant PConst_string("abc@,def\n\nghi",None)
+ Pexp_constant PConst_string("abc@,def\nghi",None)
]