feat: Add filterStrict() and flatten() methods to ArrayList

.github/workflows/phpstan.yml

@@ -68,4 +68,4 @@ jobs:
           key: "phpstan-result-cache-${{ github.run_id }}"
 
       - name: Run PHPUnit tests
-        run: vendor/bin/phpunit --configuration=phpunit.xml.dist --testdox --colors=always
+        run: php -d zend.assertions=1 vendor/bin/phpunit --configuration=phpunit.xml.dist --testdox --colors=always

src/Collection/ArrayList.php

@@ -253,7 +253,7 @@ final public function firstOrFail(?Closure $closure = null)
     #[Override]
     final public function sole(?Closure $closure = null)
     {
-        $items = $closure === null ? new static($this->elements) : $this->filter($closure);
+        $items = $closure === null ? new static($this->elements) : $this->filterStrict($closure);
         $count = $items->count();
 
         if ($count === 0) {
@@ -337,17 +337,47 @@ final public function mapStrict(Closure $closure): static
         return new static(array_map($closure, $this->elements, $keys));
     }
 
+    /**
+     * @template TFlatMapValue
+     * @param  Closure(TValue,int): iterable<TFlatMapValue> $closure
+     * @return self<TFlatMapValue>
+     */
+    #[Override]
+    final public function flatMap(Closure $closure): self
+    {
+        $result = [];
+
+        foreach ($this->elements as $index => $item) {
+            $mapped = $closure($item, $index);
+
+            foreach ($mapped as $subItem) {
+                $result[] = $subItem;
+            }
+        }
+
+        return new self($result);
+    }
+
+    /**
+     * @param  Closure(TValue,int): bool $closure
+     * @return self<TValue>
+     */
     #[Override]
-    final public function filter(Closure $closure): static
+    final public function filter(Closure $closure): self
     {
+        return new self(array_filter($this->elements, $closure, ARRAY_FILTER_USE_BOTH));
+    }
 
+    #[Override]
+    final public function filterStrict(Closure $closure): static
+    {
         return new static(array_filter($this->elements, $closure, ARRAY_FILTER_USE_BOTH));
     }
 
     #[Override]
     final public function reject(Closure $closure): static
     {
-        return $this->filter(static fn ($value, $key) => !$closure($value, $key));
+        return $this->filterStrict(static fn ($value, $key) => !$closure($value, $key));
     }
 
     #[Override]

src/Collection/List/IArrayList.php

@@ -125,6 +125,14 @@ public function merge(self $other): self;
      */
     public function map(Closure $closure): self;
 
+    /**
+     * 各要素に関数を適用し、結果を平坦化したコレクションを返す
+     * @template TFlatMapValue
+     * @param  Closure(TValue,int): iterable<TFlatMapValue> $closure
+     * @return self<TFlatMapValue>
+     */
+    public function flatMap(Closure $closure): self;
+
     /**
      * @param  Closure(TValue,int): TValue $closure
      * @return static<TValue>
@@ -134,9 +142,17 @@ public function mapStrict(Closure $closure): static;
     /**
      * 与えられた真理判定に合格するすべての要素のコレクションを作成する。
      * @param  Closure(TValue,int): bool $closure
+     * @return self<TValue>
+     */
+    public function filter(Closure $closure): self;
+
+    /**
+     * 与えられた真理判定に合格するすべての要素のコレクションを作成する。
+     * (strict version - 正確な型を保持)
+     * @param  Closure(TValue,int): bool $closure
      * @return static<TValue>
      */
-    public function filter(Closure $closure): static;
+    public function filterStrict(Closure $closure): static;
 
     /**
      * 与えられた真理判定に合格しないすべての要素のコレクションを作成する。

src/ValueObjectList.php

@@ -27,7 +27,7 @@ public function has(IValueObject $element): bool
      */
     public function remove(IValueObject $element): static
     {
-        return $this->filter(static fn (IValueObject $e) => !$e->equals($element));
+        return $this->filterStrict(static fn (IValueObject $e) => !$e->equals($element));
     }
 
     /**
@@ -45,6 +45,6 @@ public function put(IValueObject $element): static
      */
     public function diff(self $other): static
     {
-        return $this->filter(static fn (IValueObject $e) => !$other->has($e));
+        return $this->filterStrict(static fn (IValueObject $e) => !$other->has($e));
     }
 }

tests/Unit/Collection/ArrayListTest.php

@@ -467,4 +467,76 @@ public function sort関数で要素をソートしたコレクションが取得
         // 元のコレクションは変更されない（イミュータブル）
         $this->assertEquals([3, 1, 4, 2, 5], $collection->toArray());
     }
+
+    #[Test]
+    public function filter関数でselfを返すことができる(): void
+    {
+        $collection = ArrayList::from([1, 2, 3, 4, 5]);
+
+        $filtered = $collection->filter(static fn ($value) => $value % 2 === 0);
+
+        // 戻り値がArrayListインスタンス（self）であることを確認
+        $this->assertInstanceOf(ArrayList::class, $filtered);
+        $this->assertEquals([1 => 2, 3 => 4], $filtered->toArray());
+
+        // 元のコレクションは変更されない（イミュータブル）
+        $this->assertEquals([1, 2, 3, 4, 5], $collection->toArray());
+    }
+
+    #[Test]
+    public function filterStrict関数でstaticを返すことができる(): void
+    {
+        $collection = ArrayList::from([1, 2, 3, 4, 5]);
+
+        $filtered = $collection->filterStrict(static fn ($value) => $value % 2 === 0);
+
+        // 戻り値が正確な型（static）であることを確認
+        $this->assertInstanceOf(ArrayList::class, $filtered);
+        $this->assertEquals([1 => 2, 3 => 4], $filtered->toArray());
+
+        // 元のコレクションは変更されない（イミュータブル）
+        $this->assertEquals([1, 2, 3, 4, 5], $collection->toArray());
+    }
+
+    #[Test]
+    public function flatMap関数で各要素を変換して平坦化できる(): void
+    {
+        // 基本的な変換（各数値を2倍にして配列に包む）
+        $collection = ArrayList::from([1, 2, 3]);
+        $mapped = $collection->flatMap(static fn ($value) => [$value * 2]);
+
+        $this->assertInstanceOf(ArrayList::class, $mapped);
+        $this->assertEquals([2, 4, 6], $mapped->toArray());
+
+        // 各要素を複数の要素に展開
+        $collection2 = ArrayList::from([1, 2, 3]);
+        $expanded = $collection2->flatMap(static fn ($value) => [$value, $value * 10]);
+
+        $this->assertEquals([1, 10, 2, 20, 3, 30], $expanded->toArray());
+
+        // 空の配列を返す場合
+        $collection3 = ArrayList::from([1, 2, 3]);
+        $filtered = $collection3->flatMap(static fn ($value) => $value % 2 === 0 ? [$value] : []);
+
+        $this->assertEquals([2], $filtered->toArray());
+
+        // 2次元配列の平坦化（従来のflattenと同等の動作）
+        $collection4 = ArrayList::from([[1, 2], [3, 4], [5, 6]]);
+        $flattened = $collection4->flatMap(static fn ($array) => $array);
+
+        $this->assertEquals([1, 2, 3, 4, 5, 6], $flattened->toArray());
+        // 元のコレクションは変更されない（イミュータブル）
+        $this->assertEquals([1, 2, 3], $collection->toArray());
+
+        // objectの2次元配列の平坦化（従来のflattenと同等の動作）
+        $collection5 = ArrayList::from([
+            ArrayList::from([1, 2]),
+            ArrayList::from([3, 4]),
+            ArrayList::from([5, 6]),
+        ]);
+        $flattenedObjects = $collection5->flatMap(static fn ($array) => $array);
+        $this->assertEquals([1, 2, 3, 4, 5, 6], $flattenedObjects->toArray());
+        // 元のコレクションは変更されない（イミュータブル）
+        $this->assertEquals([ArrayList::from([1, 2]), ArrayList::from([3, 4]), ArrayList::from([5, 6])], $collection5->toArray());
+    }
 }