Repository navigation
Do not allow addition/subtractions with null and number #4059
Description
Addition and subtraction with null values results in string concatenation rather than an error.
@debug 2% + null - 10px; // -> 2%-10pxDoing the same operation within calc() results on the expected error.
@debug calc(2% + null - 10px);
// This expression can't be used in a calculation.
// ╷
// 2 │ @debug calc(2% + null - 10px);
// │ ^^^^
// ╵
// - 2:18 root stylesheetI'm not sure whether this requires a spec change, or whether the spec is right but the implementation isn't
Activity
nex3 commentedon Apr 2, 2025
The spec doesn't cover this at all currently, so it does require a spec change.
stof commentedon Jun 13, 2025
why would "number and null" suddenly become forbidden but not "number and string" then ? should this apply to any type used with numbers instead ?
SassNumber.plusandSassNumber.minushas 3 cases only in dart-sass:other is SassNumber: perform number additionother is SassColor: trigger error due to forbidding color math (which was supported in ruby-sass and libsass)Value.plusorValue.minuswhich treats+as concatenation and-as a delimited concatenationNote that the documentation of https://sass-lang.com/documentation/operators/string/ does not exactly match the behavior (it says numbers cannot be used at all on the left of string operators).
So even though the spec does not say anything (because the spec for the
stringtype is not written at all, and no spec is written either for binary operators), the documentation says something (and it does not match the implementation)nex3 commentedon Jun 14, 2025
I think it makes sense to still do string concatenation when strings are already involved (which is very common behavior across programming languages), but defaulting to string concatenation when none of the operands are strings is likely to be unexpected.