Fix UnderflowException in map

composer.json

@@ -18,11 +18,11 @@
 	"require-dev": {
 		"squizlabs/php_codesniffer": "^3.9",
 		"stefna/codestyle": "^1.15",
-		"phpstan/phpstan": "^1.10",
+		"phpstan/phpstan": "^2.1",
 		"bnf/phpstan-psr-container": "^1.0",
 		"phpunit/phpunit": "^10.5",
-		"phpstan/phpstan-phpunit": "^1.1",
-		"tomasvotruba/type-coverage": "^0.3 || ^1.0",
+		"phpstan/phpstan-phpunit": "^2.0",
+		"tomasvotruba/type-coverage": "^2.0",
 		"phpstan/extension-installer": "^1.3"
 	},
 	"autoload": {

phpstan.neon

@@ -2,6 +2,7 @@ parameters:
 	level: max
 	paths:
 		- src
+		- tests
 	type_coverage:
 		return_type: 90
 		param_type: 100

src/AbstractListCollection.php

@@ -191,8 +191,12 @@ public function filter(callable $filter): static
 
 	public function map(callable $callback): ListCollection
 	{
+		if ($this->data->isEmpty()) {
+			return new GenericListCollection($this->collectionType); // @phpstan-ignore return.type
+		}
 		$newData = $this->data->map($callback);
-		$collection = new GenericListCollection(get_class($newData->first()));
+		$collectionType = $newData->first()::class;
+		$collection = new GenericListCollection($collectionType);
 		$collection->data = $newData;
 		return $collection;
 	}
@@ -211,7 +215,7 @@ public function indexBy(callable $callback): MapCollection
 
 	public function column(callable $callback): array
 	{
-		return $this->data->map($callback)->toArray();
+		return array_values($this->data->map($callback)->toArray());
 	}
 
 	public function merge(Collection ...$collections): static

src/AbstractMapCollection.php

@@ -31,10 +31,11 @@ public function __construct(
 		if (!isset($this->collectionType) && isset(static::$defaultCollectionType)) {
 			$this->collectionType = static::$defaultCollectionType;
 		}
-		$this->data = new Map();
+		$this->data = new Map(); // @phpstan-ignore assign.propertyType
 		// Invoke offsetSet() for each value added; in this way, sub-classes
 		// may provide additional logic about values added to the array object.
 		foreach ($data as $key => $value) {
+			// @phpstan-ignore function.alreadyNarrowedType
 			if (!is_string($key)) {
 				throw new \BadMethodCallException('Must specify key');
 			}
@@ -83,6 +84,7 @@ public function offsetSet(mixed $offset, mixed $value): void
 		if (!$value instanceof $this->collectionType) {
 			throw new \TypeError('Invalid type for collection. Expected: ' . $this->collectionType);
 		}
+		// @phpstan-ignore function.alreadyNarrowedType
 		if (!is_string($offset)) {
 			throw new \InvalidArgumentException('Offset must be of type string');
 		}
@@ -108,7 +110,7 @@ public function count(): int
 
 	public function clear(): void
 	{
-		$this->data = new Map();
+		$this->data = new Map(); // @phpstan-ignore assign.propertyType
 	}
 
 	/**
@@ -204,6 +206,9 @@ public function filter(callable $filter): static
 	 */
 	public function map(callable $callback): MapCollection
 	{
+		if ($this->data->isEmpty()) {
+			return new GenericMapCollection($this->collectionType); // @phpstan-ignore return.type
+		}
 		$newData = $this->data->map($callback);
 		$collection = new GenericMapCollection(get_class($newData->first()->value));
 		$collection->data = $newData;

tests/GenericListCollectionTest.php

@@ -178,6 +178,18 @@ public function testMap(): void
 		$this->assertSame($value, $newCollection->first()?->value);
 	}
 
+	public function testMapOnEmptyCollection(): void
+	{
+		$collection1 = new GenericListCollection(RandomEntity::class, []);
+
+		$newCollection = $collection1->map(fn (RandomEntity $entity): ExtraEntity => new ExtraEntity((string)$entity->value));
+
+		$this->assertNotSame($collection1, $newCollection);
+		$this->assertCount(0, $newCollection);
+		// the collection type stays the same since the collection is empty and hence can't change
+		$this->assertSame($collection1->getType(), $newCollection->getType());
+	}
+
 	public function testFilter(): void
 	{
 		$collection1 = new GenericListCollection(RandomEntity::class, [
@@ -226,7 +238,7 @@ public function testIndexBy(): void
 		$index = 1;
 		foreach ($mapCollection as $key => $value) {
 			$this->assertSame('index' . $index, $key);
-			$this->assertInstanceOf(ExtraEntity::class, $value);
+			$this->assertInstanceOf(ExtraEntity::class, $value); // @phpstan-ignore method.alreadyNarrowedType
 			$index++;
 		}
 	}
@@ -274,7 +286,7 @@ public function testColumn(): void
 		$values = $collection1->column(fn (RandomEntity $r) => $r->value);
 
 		$this->assertCount(5, $values);
-		$this->assertIsList($values);
+		$this->assertIsList($values); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertSame([1, 2, 3, 4, 5], $values);
 	}
 

tests/GenericMapCollectionTest.php

@@ -201,6 +201,18 @@ public function testMap(): void
 		$this->assertSame($value, $newCollection->first()?->value);
 	}
 
+	public function testMapOnEmptyCollection(): void
+	{
+		$collection1 = new GenericMapCollection(RandomEntity::class, []);
+
+		$newCollection = $collection1->map(fn (string $key, RandomEntity $entity): ExtraEntity => new ExtraEntity((string)$entity->value));
+
+		$this->assertNotSame($collection1, $newCollection);
+		$this->assertCount(0, $newCollection);
+		// the collection type stays the same since the collection is empty and hence can't change
+		$this->assertSame($collection1->getType(), $newCollection->getType());
+	}
+
 	public function testFilter(): void
 	{
 		$collection1 = new GenericMapCollection(RandomEntity::class, [
@@ -297,7 +309,7 @@ public function testIndexBy(): void
 		$index = 1;
 		foreach ($mapCollection as $key => $value) {
 			$this->assertSame('index' . $index, $key);
-			$this->assertInstanceOf(ExtraEntity::class, $value);
+			$this->assertInstanceOf(ExtraEntity::class, $value); // @phpstan-ignore method.alreadyNarrowedType
 			$index++;
 		}
 	}
@@ -324,7 +336,7 @@ public function testColumn(): void
 		$values = $collection1->column(fn (RandomEntity $r) => $r->value);
 
 		$this->assertCount(5, $values);
-		$this->assertIsList($values);
+		$this->assertIsList($values); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertSame(['1', '2', '3', '4', '5'], $values);
 	}
 

tests/ScalarMapTest.php

@@ -20,7 +20,7 @@ public function testGetStringWithDefaultValue(): void
 	{
 		$map = $this->createMap();
 		$value = $map->getString('testStringNotFound', 'random');
-		$this->assertIsString($value);
+		$this->assertIsString($value); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertSame('random', $value);
 	}
 
@@ -55,7 +55,7 @@ public function testGetIntWithDefaultValue(): void
 	{
 		$map = $this->createMap();
 		$value = $map->getInt('testIntNotFound', 42);
-		$this->assertIsInt($value);
+		$this->assertIsInt($value); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertSame(42, $value);
 	}
 
@@ -76,7 +76,7 @@ public function testGetFloatWithDefaultValue(): void
 	{
 		$map = $this->createMap();
 		$value = $map->getFloat('testFloatNotFound', 42.1);
-		$this->assertIsFloat($value);
+		$this->assertIsFloat($value); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertSame(42.1, $value);
 	}
 
@@ -100,7 +100,7 @@ public function testGetBoolWithDefaultValue(): void
 	{
 		$map = $this->createMap();
 		$value = $map->getBool('testBoolNotFound', true);
-		$this->assertIsBool($value);
+		$this->assertIsBool($value); // @phpstan-ignore method.alreadyNarrowedType
 		$this->assertTrue($value);
 	}