cascading await

[DartBot]

This issue was originally filed by [email protected]

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Would it be possible to make the following work?

testDriver..await deleteAll()
  ..await createNew()
  ..await refresh();

[lrhn]

Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

[lrhn]

I don't see this syntax happening. I'd put my money on #25986 instead, introducing a suffix form of await, so you could write, e.g.,

testDriver..deleteAll().await
  ..createNew().await
  ..refresh().await;

(or whatever syntax would be used for that).

The problem with allowing prefix operators to be used infix is that it's not clear how they bind.
If you write testDriver..await foo().bar(), are you awaiting foo() or foo().bar().
How about a..await b[42] or a..await b.foo()[42].

So, probably won't happen as this.

[subzero911]

+1, just made a mistake today:

final auth = await context.read<AuthStore>()..login();

this wouldn't work because I need to await login, not a read method
the only way is

final auth = context.read<AuthStore>();
await auth.login()

The desirable syntax is final auth = context.read<AuthStore>()..await login();... Things like login().await are counter-intuitive IMO.

[HannesGitH]

The problem with allowing prefix operators to be used infix is that it's not clear how they bind.
If you write testDriver..await foo().bar(), are you awaiting foo() or foo().bar().
How about a..await b[42] or a..await b.foo()[42].

how does that differ from normal await ? e.g.

if(await foo().bar()) // calls foo and awaits its bar
if((await foo()).bar()) // awaits foo and then calls its bar

and we know that, no ambiguity..
on the other hand a new syntax like

if(foo().bar().await.baz())

would probably confuse people as dart does not use .await as a postfix normally
and i dont really see how cascading differs from normal code/invocation

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but, tbh, on the other hand I already find

final auth = await context.read<AuthStore>()..login();

somewhat ambigous already, as i thought cascading async calls would work similar to promise/future chaining à la

var auth;
await asyncGet<AuthStore>().then(init).then(login).then((a)=>auth=a)

which makes the whole call a future as soon as one part is async, and awaiting would await all calls and make

final auth = await asyncGet<AuthStore>()..init()..login();

work as @subzero911 (and I, which brought me here in the first place) thought (intuitively without actually thinking about it) it would