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Introduce IterableMapEntryExtension for use with Map.entries. (#715)
* Introduce `IterableMapEntryExtension` for use with `Map.entries`. **Example**: ```dart final myMap = { 'foo': 42, 'bar': -1, 'foobar': 21, }; // myMap without negative values myMap.entries.whereValue((v) => v >= 0).toMap(); // myMap, but only keys that start with 'foo' myMap.entries.whereKey((k) => k.startsWith('foo')).toMap(); ```
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‎pkgs/collection/CHANGELOG.md

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@@ -1,3 +1,7 @@
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## 1.19.1-wip
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- Add `IterableMapEntryExtension` for working on `Map` as a list of pairs, using
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`Map.entries`.
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## 1.19.1
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- Move to `dart-lang/core` monorepo.

‎pkgs/collection/lib/src/iterable_extensions.dart

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@@ -914,6 +914,43 @@ extension IterableIterableExtension<T> on Iterable<Iterable<T>> {
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};
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}
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/// Extension on iterables of [MapEntry].
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///
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/// An [Iterable<MapEntry>] is obtained using [Map.entries]. These extensions
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/// facilitates working directly on the entries of a [Map].
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extension IterableMapEntryExtension<K, V> on Iterable<MapEntry<K, V>> {
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/// The elements whose [MapEntry.key] values satisfy [test].
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///
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/// The resulting iterable is lazily computing its elements
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/// based on the elements this iterable.
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Iterable<MapEntry<K, V>> whereKey(bool Function(K) test) =>
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where((e) => test(e.key));
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/// The elements whose [MapEntry.value] values satisfy [test].
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///
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/// The resulting iterable is lazily computing its elements
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/// based on the elements this iterable.
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Iterable<MapEntry<K, V>> whereValue(bool Function(V) test) =>
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where((e) => test(e.value));
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/// A new lazy [Iterable] of the [MapEntry.key]s of these entries.
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///
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/// Do not use this getter as `map.entries.keys`, just use `map.keys`
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/// directly.
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Iterable<K> get keys => map((e) => e.key);
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/// A new lazy [Iterable] of the [MapEntry.value]s of these entries.
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///
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/// Do not use this getter as `map.entries.values`, just use `map.values`
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/// directly.
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Iterable<V> get values => map((e) => e.value);
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/// Create a [Map<K, V>] from all elements.
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///
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/// This is a short-hand for [Map.fromEntries].
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Map<K, V> toMap() => Map<K, V>.fromEntries(this);
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}
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/// Extensions that apply to iterables of [Comparable] elements.
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///
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/// These operations can assume that the elements have a natural ordering,

‎pkgs/collection/pubspec.yaml

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@@ -1,5 +1,5 @@
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name: collection
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version: 1.19.1
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version: 1.19.1-wip
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description: >-
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Collections and utilities functions and classes related to collections.
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repository: https://github.com/dart-lang/core/tree/main/pkgs/collection

‎pkgs/collection/test/extensions_test.dart

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@@ -1122,6 +1122,180 @@ void main() {
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});
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});
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});
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group('of MapEntry', () {
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group('.whereKey', () {
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test('empty', () {
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expect(
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iterable(<MapEntry<String, int>>[]).whereKey(unreachable),
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isEmpty,
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);
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});
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test('single', () {
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expect(
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iterable([const MapEntry('a', 1)]).whereKey((k) => k == 'a'),
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[const MapEntry('a', 1)],
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);
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expect(
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iterable([const MapEntry('a', 1)]).whereKey((k) => k == 'b'),
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isEmpty,
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);
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});
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test('multiple', () {
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereKey((k) => k == 'a'),
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[const MapEntry('a', 1)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereKey((k) => k == 'b'),
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[const MapEntry('b', 2)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereKey((k) => k != 'c'),
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[const MapEntry('a', 1), const MapEntry('b', 2)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('a', 3),
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]).whereKey((k) => k == 'a'),
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[const MapEntry('a', 1), const MapEntry('a', 3)],
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);
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});
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});
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group('.whereValue', () {
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test('empty', () {
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expect(
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iterable(<MapEntry<String, int>>[]).whereValue(unreachable),
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isEmpty,
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);
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});
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test('single', () {
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expect(
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iterable([const MapEntry('a', 1)]).whereValue((v) => v == 1),
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[const MapEntry('a', 1)],
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);
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expect(
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iterable([const MapEntry('a', 1)]).whereValue((v) => v == 2),
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isEmpty,
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);
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});
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test('multiple', () {
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereValue((v) => v == 1),
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[const MapEntry('a', 1)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereValue((v) => v == 2),
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[const MapEntry('b', 2)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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]).whereValue((v) => v != 3),
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[const MapEntry('a', 1), const MapEntry('b', 2)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('c', 1),
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]).whereValue((v) => v == 1),
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[const MapEntry('a', 1), const MapEntry('c', 1)],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('a', 1),
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]).whereValue((v) => v == 1),
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[const MapEntry('a', 1), const MapEntry('a', 1)],
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);
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});
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});
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group('.keys', () {
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test('empty', () {
1234+
expect(iterable(<MapEntry<String, int>>[]).keys, isEmpty);
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});
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test('single', () {
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expect(iterable([const MapEntry('a', 1)]).keys, ['a']);
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});
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test('multiple', () {
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expect(
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iterable([const MapEntry('a', 1), const MapEntry('b', 2)]).keys,
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['a', 'b'],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('a', 3),
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]).keys,
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['a', 'b', 'a'],
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);
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});
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});
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group('.values', () {
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test('empty', () {
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expect(iterable(<MapEntry<String, int>>[]).values, isEmpty);
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});
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test('single', () {
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expect(iterable([const MapEntry('a', 1)]).values, [1]);
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});
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test('multiple', () {
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expect(
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iterable([const MapEntry('a', 1), const MapEntry('b', 2)]).values,
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[1, 2],
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('a', 3),
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]).values,
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[1, 2, 3],
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);
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});
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});
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group('.toMap', () {
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test('empty', () {
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expect(iterable(<MapEntry<String, int>>[]).toMap(), <String, int>{});
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});
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test('single', () {
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expect(iterable([const MapEntry('a', 1)]).toMap(), {'a': 1});
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});
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test('multiple', () {
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expect(
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iterable([const MapEntry('a', 1), const MapEntry('b', 2)]).toMap(),
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{'a': 1, 'b': 2},
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);
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expect(
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iterable([
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const MapEntry('a', 1),
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const MapEntry('b', 2),
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const MapEntry('a', 3),
1293+
]).toMap(),
1294+
{'b': 2, 'a': 3},
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);
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});
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});
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});
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group('of comparable', () {
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group('.min', () {
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test('empty', () {

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