Add Iterable.empty constructor.

Add Iterable.empty constructor.

Convenience constructor giving an easy/quick way to create an empty iterable.

R=sgjesse@google.com

Committed: https://github.com/dart-lang/sdk/commit/dcf0286f5385187a68ce9e66318d3bf19abf454b

[Lasse Reichstein Nielsen, 2015-05-21 08:20:40]

lrn@google.com changed reviewers:
+ sgjesse@google.com

[Søren Gjesse, 2015-05-21 09:10:06]

lgtm

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart
File sdk/lib/core/iterable.dart (right):

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart#...
sdk/lib/core/iterable.dart:111: * the iterable you would otherwise is always
empty.
Seems like there is a word missing after "otherwise".

https://codereview.chromium.org/1152483002/diff/1/tests/corelib/iterable_empt...
File tests/corelib/iterable_empty_test.dart (right):

https://codereview.chromium.org/1152483002/diff/1/tests/corelib/iterable_empt...
tests/corelib/iterable_empty_test.dart:20: Expect.throws(() =>
it.singleWhere((_) => true), (e) => e is StateError, name);
Long line.

[kevmoo, 2015-05-21 15:07:06]

kevmoo@google.com changed reviewers:
+ kevmoo@google.com

[kevmoo, 2015-05-21 15:07:06]

DCQ

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart
File sdk/lib/core/iterable.dart (right):

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart#...
sdk/lib/core/iterable.dart:113: const factory Iterable.empty() =
EmptyIterable<E>;
Why is this useful over using `const []`?

[Lasse Reichstein Nielsen, 2015-05-21 15:16:51]

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart
File sdk/lib/core/iterable.dart (right):

https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart#...
sdk/lib/core/iterable.dart:113: const factory Iterable.empty() =
EmptyIterable<E>;
Because const[] is a List, not just an Iterable.
You shouldn't return a class that is more capable than our interface requires,
at least not in library code, because sooner or later someone is going to rely
on it.

I was about to do a new DelegatingIterable(const []) when I decided that I
should just get around to add this constructor (which I had plans for before I
even started working on the libraries :).

And the class already existed, so it was either moving it to a public library
(from dart:_internal) or giving access to it like this.

[kevmoo, 2015-05-21 16:05:08]

On 2015/05/21 15:16:51, Lasse Reichstein Nielsen wrote:
> https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart
> File sdk/lib/core/iterable.dart (right):
> 
>
https://codereview.chromium.org/1152483002/diff/1/sdk/lib/core/iterable.dart#...
> sdk/lib/core/iterable.dart:113: const factory Iterable.empty() =
> EmptyIterable<E>;
> Because const[] is a List, not just an Iterable.
> You shouldn't return a class that is more capable than our interface requires,
> at least not in library code, because sooner or later someone is going to rely
> on it.
> 
> I was about to do a new DelegatingIterable(const []) when I decided that I
> should just get around to add this constructor (which I had plans for before I
> even started working on the libraries :).
> 
> And the class already existed, so it was either moving it to a public library
> (from dart:_internal) or giving access to it like this.

Makes sense. Thanks for clarifying.

[Lasse Reichstein Nielsen, 2015-05-22 08:40:02]

Committed patchset #2 (id:20001) manually as
dcf0286f5385187a68ce9e66318d3bf19abf454b (presubmit successful).

[kevmoo, 2015-05-23 00:20:23]

On 2015/05/22 08:40:02, Lasse Reichstein Nielsen wrote:
> Committed patchset #2 (id:20001) manually as
> dcf0286f5385187a68ce9e66318d3bf19abf454b (presubmit successful).

Please add an entry to the CHANGELOG, too. :-)