Dict\flatten

Summary: Adding for parity with `{Keyset, Vec}\flatten`.

Reviewed By: fredemmott

Differential Revision: D6011560

fbshipit-source-id: 3527e9e5358a6795242f56dc5dd6ffe34e4a9cad

src/dict/combine.php

@@ -41,11 +41,5 @@ function associate<Tk as arraykey, Tv>(
 function merge<Tk, Tv>(
  KeyedTraversable<Tk, Tv> ...$traversables
 ): dict<Tk, Tv> {
- $result = dict[];
- foreach ($traversables as $traversable) {
- foreach ($traversable as $key => $value) {
- $result[$key] = $value;
- }
- }
- return $result;
+ return namespace\flatten($traversables);
 }

src/dict/transform.php

@@ -47,6 +47,25 @@ function count_values<Tv as arraykey>(
  return $result;
 }
 
+/**
+ * Returns a new dict formed by merging the KeyedTraversable elements of the
+ * given Traversable. In the case of duplicate keys, later values will overwrite
+ * the previous ones.
+ *
+ * For a fixed number of KeyedTraversables, see `Dict\merge`.
+ */
+function flatten<Tk, Tv>(
+ Traversable<KeyedTraversable<Tk, Tv>> $traversables,
+): dict<Tk, Tv> {
+ $result = dict[];
+ foreach ($traversables as $traversable) {
+ foreach ($traversable as $key => $value) {
+ $result[$key] = $value;
+ }
+ }
+ return $result;
+}
+
 /**
  * Returns a new dict where all the given keys map to the given value.
  */

tests/dict/DictTransformTest.php

@@ -136,6 +136,83 @@ public function testFillKeys<Tk as arraykey, Tv>(
  expect(Dict\fill_keys($keys, $value))->toBeSame($expected);
  }
 
+ public static function provideTestFlatten(): array<mixed> {
+ return array(
+ tuple(
+ array(),
+ dict[],
+ ),
+ tuple(
+ array(
+ array(
+ 'one' => 'one',
+ 'two' => 'two',
+ ),
+ array(
+ 'three' => 'three',
+ 'one' => 3,
+ ),
+ Map {
+ 'four' => null,
+ },
+ ),
+ dict[
+ 'one' => 3,
+ 'two' => 'two',
+ 'three' => 'three',
+ 'four' => null,
+ ],
+ ),
+ tuple(
+ array(
+ HackLibTestTraversables::getKeyedIterator(array(
+ 'foo' => 'foo',
+ 'bar' => 'bar',
+ 'baz' => array(1, 2, 3),
+ )),
+ dict[
+ 'bar' => 'barbar',
+ ],
+ Vector {'I should feel bad for doing this', 'But yolo'},
+ array(
+ '1' => 'gross array behavior',
+ ),
+ Set {'bloop'},
+ ),
+ dict[
+ 'foo' => 'foo',
+ 'bar' => 'barbar',
+ 'baz' => array(1, 2, 3),
+ 0 => 'I should feel bad for doing this',
+ 1 => 'gross array behavior',
+ 'bloop' => 'bloop',
+ ],
+ ),
+ tuple(
+ HackLibTestTraversables::getIterator(array(
+ vec['zero'],
+ array(1 => 'one'),
+ dict[2 => 'two'],
+ Map {3 => 'three'},
+ )),
+ dict[
+ 0 => 'zero',
+ 1 => 'one',
+ 2 => 'two',
+ 3 => 'three',
+ ],
+ ),
+ );
+ }
+
+ /** @dataProvider provideTestFlatten */
+ public function testFlatten<Tk, Tv>(
+ Traversable<KeyedTraversable<Tk, Tv>> $traversables,
+ dict<Tk, Tv> $expected,
+ ): void {
+ expect(Dict\flatten($traversables))->toBeSame($expected);
+ }
+
  public static function provideTestFlip(): array<mixed> {
  return array(
  tuple(