RxJS v6.3 pipe - How to use it? - rxjs

Question

I just created a new Angular app that installed the new RxJS v6.3 (released 6 days ago), which "fixed" a problem with pipe and strong typing.
With v6.2 I could specify only the final returning value of the pipe (in this case, .pipe<User>, like this:
getStatus(): Observable<User> {
return this.http.get('/user/status')
.pipe<User>(
tap(foo, bar),
finalize(() => this.requestEnded()),
map((resp) => new User(resp.user)));
}
But in the new version they removed that possibility in the Observable class (they fixed this line from v6.2.2, to this in v6.3). The IDE complains with this message:
Expected at least 0 arguments, but got 1 or more.
Now I am forced to specify types for every function in the pipe, something like this:
getStatus(): Observable<User> {
return this.http.get('/user/status')
// If I have 3 piped functions I have to specify all 3 types
.pipe<{}, {}, User>(
tap(foo, bar),
finalize(() => this.requestEnded()),
// I even have to specify type for this parameter (resp)
map((resp: {user}) => new User(resp.user)));
}
Was this really intended? Note that this is a "fix" to pipe, which means to me that pipe was always supposed to work like that. Or am I using it the wrong way?
I even had this function that worked nicely, I just passed in some "common pipes" that I wanted to execute for every request:
logIn(username: string, password: string, remember: boolean) {
return this.http.post('/user/login', { username, password, remember })
.pipe<User>(
...this.commonPipes(),
map(resp => new User(resp.user)));
}
But now, how am I supposed to specify types for that?
This change was introduced in v6.3 which says it "fixes" some error with pipe (it references this issue). I write "fixes" because for me it broke things, it's not backwards compatible, and I haven't found a "how to upgrade" guide that explains how to use the new, fixed pipe().

Answer 1

The problem was that the spread syntax could only be used in a couple of versions in which the signatures for pipe were 'fixed'. However, those 'fixes' essentially broke all type checking for pipe - which was far worse, so they were reverted and changed again.
As noted in this issue, using the spread syntax with pipe requires TypeScript 3.0 - as it supports tuple parameter extraction and spreading.
As an alternative to having commonPipes return an array of operators, you could look at using the static pipe function to compose the operators into a single operator that can then be passed to an observable's pipe method.
Have a look at my Combining Operators article.