Stricter type definition of Subject #5307
Merged
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Description:
Make type definition of
Subject
more strict to avoid common bugs when using Subject.Related issue (if exists):
This issue been discussed extensively in #2852 and #5066 .
Sensitive points
As discussed in the issues linked above, it is possible to omit the argument to
next
when the Subject is of typeSubject<void>
.When the template type is anything other than
void
, then an argument fornext
is required.The primary case where this can be a problem is when people instantiate
Subject<any>
and then usesubject.next()
with no arguments. This will break.The present change makes the default template type of Subject
void
instead ofany
. This means that when you writenew Subject()
, you get aSubject<void>
(instead ofSubject<any>
) and are therefore able to writesubject.next()
orsubject.next(value)
ifvalue
is eitherany
orundefined
.Other good candidates for default template type are
unknown
andany
. We can discuss whethervoid
is the best choice here, I am not completely sure yet.