Misuse of `empty` psalm type
zerkms opened this issue · comments
Assert::isEmpty is typed as @psalm-assert empty $value
Assert::notEmpty is typed as @psalm-assert !empty $value
I think both are wrong.
https://psalm.dev/docs/annotating_code/type_syntax/atomic_types/
empty - a type that represents a lack of type - not just a lack of type information (that's where mixed is useful) but where there can be no type. A good example is the type of the empty array []. Psalm types this as array<empty, empty>.
So I believe there is no psalm type currently available to express empty'ness or non-empty'ness in the php values meaning.
Oops, accidentally closed, reopening.
Seems coherent:
https://psalm.dev/r/7972caa66e
When you expect empty, Psalm will reject any value.
When you expect !empty, Psalm will accept any value.
It would have been a different story if we were able to do this though:
@psalm-assert ($value is string : empty-string : ($value is array ? empty-array : mixed) $value
Unfortunately, it only works with returns right now
When you expect empty, Psalm will reject any value.
This is wrong, '', [], 0 etc are valid empty values (as per the Assert::isEmpty semantics).
Psalm's empty (lack of) type and php's empty() function have different incompatible semantics, even though they are named the same.
Ok, wait a second, it looks like psalm combines empty with the already currently known type, and produces a context-specific intersection.
In that case I'm indeed wrong.
Closing this as invalid, thanks!