[TypeDeclaration] Add AddArrowFunctionReturnTypeRector (#2933)

* [TypeDeclaration] Add AddArrowFunctionReturnTypeRector

* [ci-review] Rector Rectify

* [ci-review] Rector Rectify

* final touch: clean up

* final touch: clean up

* final touch: test for return declaration exists

* fix min php version

Co-authored-by: GitHub Action <action@github.com>

config/set/type-declaration.php

@@ -3,6 +3,7 @@
 declare(strict_types=1);
 
 use Rector\Config\RectorConfig;
+use Rector\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector;
 use Rector\TypeDeclaration\Rector\ClassMethod\AddArrayParamDocTypeRector;
 use Rector\TypeDeclaration\Rector\ClassMethod\AddArrayReturnDocTypeRector;
 use Rector\TypeDeclaration\Rector\ClassMethod\AddReturnTypeDeclarationBasedOnParentClassMethodRector;
@@ -22,6 +23,7 @@
         ReturnTypeDeclarationRector::class,
         PropertyTypeDeclarationRector::class,
         AddClosureReturnTypeRector::class,
+        AddArrowFunctionReturnTypeRector::class,
         AddArrayParamDocTypeRector::class,
         AddArrayReturnDocTypeRector::class,
         ParamTypeByMethodCallTypeRector::class,

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/AddArrowFunctionReturnTypeRectorTest.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Tests\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector;
+
+use Iterator;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class AddArrowFunctionReturnTypeRectorTest extends AbstractRectorTestCase
+{
+    /**
+     * @dataProvider provideData()
+     */
+    public function test(string $filePath): void
+    {
+        $this->doTestFile($filePath);
+    }
+
+    /**
+     * @return Iterator<array<string>>
+     */
+    public function provideData(): Iterator
+    {
+        return $this->yieldFilesFromDirectory(__DIR__ . '/Fixture');
+    }
+
+    public function provideConfigFilePath(): string
+    {
+        return __DIR__ . '/config/before_union_types.php';
+    }
+}

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/Fixture/fixture.php.inc

@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\Closure\AddClosureReturnTypeRector\Fixture;
+
+class Fixture
+{
+    public function run()
+    {
+        fn () => rand(0, 1) ? []: null;
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\Closure\AddClosureReturnTypeRector\Fixture;
+
+class Fixture
+{
+    public function run()
+    {
+        fn (): ?array => rand(0, 1) ? []: null;
+    }
+}
+
+?>

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/Fixture/skip_return_declaration_exists.php.inc

@@ -0,0 +1,11 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\Closure\AddClosureReturnTypeRector\Fixture;
+
+class SkipReturnDeclarationExists
+{
+    public function run()
+    {
+        fn (): array => [];
+    }
+}

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/FixturePhp80/fixture.php.inc

@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\Closure\AddClosureReturnTypeRector\FixturePhp80;
+
+class Fixture
+{
+    public function run()
+    {
+        fn () => rand(0, 1) ? true : (rand(0, 1) ? [] : 0);
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\Closure\AddClosureReturnTypeRector\FixturePhp80;
+
+class Fixture
+{
+    public function run()
+    {
+        fn (): array|bool|int => rand(0, 1) ? true : (rand(0, 1) ? [] : 0);
+    }
+}
+
+?>

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/Php80Test.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Tests\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector;
+
+use Iterator;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class Php80Test extends AbstractRectorTestCase
+{
+    /**
+     * @dataProvider provideData()
+     */
+    public function test(string $filePath): void
+    {
+        $this->doTestFile($filePath);
+    }
+
+    /**
+     * @return Iterator<array<string>>
+     */
+    public function provideData(): Iterator
+    {
+        return $this->yieldFilesFromDirectory(__DIR__ . '/FixturePhp80');
+    }
+
+    public function provideConfigFilePath(): string
+    {
+        return __DIR__ . '/config/union_types.php';
+    }
+}

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/config/before_union_types.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Core\ValueObject\PhpVersionFeature;
+use Rector\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector;
+
+return static function (RectorConfig $rectorConfig): void {
+    $rectorConfig->phpVersion(PhpVersionFeature::UNION_TYPES - 1);
+    $rectorConfig->rule(AddArrowFunctionReturnTypeRector::class);
+};

rules-tests/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector/config/union_types.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Core\ValueObject\PhpVersionFeature;
+use Rector\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector;
+
+return static function (RectorConfig $rectorConfig): void {
+    $rectorConfig->phpVersion(PhpVersionFeature::UNION_TYPES);
+    $rectorConfig->rule(AddArrowFunctionReturnTypeRector::class);
+};

rules/TypeDeclaration/Rector/ArrowFunction/AddArrowFunctionReturnTypeRector.php

@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\TypeDeclaration\Rector\ArrowFunction;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\ArrowFunction;
+use Rector\Core\Rector\AbstractRector;
+use Rector\Core\ValueObject\PhpVersionFeature;
+use Rector\PHPStanStaticTypeMapper\Enum\TypeKind;
+use Rector\VersionBonding\Contract\MinPhpVersionInterface;
+use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
+use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;
+
+/**
+ * @see \Rector\Tests\TypeDeclaration\Rector\ArrowFunction\AddArrowFunctionReturnTypeRector\AddArrowFunctionReturnTypeRectorTest
+ */
+final class AddArrowFunctionReturnTypeRector extends AbstractRector implements MinPhpVersionInterface
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Add known return type to arrow function', [
+            new CodeSample(
+                <<<'CODE_SAMPLE'
+fn () => [];
+CODE_SAMPLE
+                ,
+                <<<'CODE_SAMPLE'
+fn (): array => [];
+CODE_SAMPLE
+            ),
+        ]);
+    }
+
+    /**
+     * @return array<class-string<Node>>
+     */
+    public function getNodeTypes(): array
+    {
+        return [ArrowFunction::class];
+    }
+
+    /**
+     * @param ArrowFunction $node
+     */
+    public function refactor(Node $node): ?Node
+    {
+        if ($node->returnType !== null) {
+            return null;
+        }
+
+        $type = $this->getType($node->expr);
+        $returnTypeNode = $this->staticTypeMapper->mapPHPStanTypeToPhpParserNode($type, TypeKind::RETURN);
+
+        if ($returnTypeNode === null) {
+            return null;
+        }
+
+        $node->returnType = $returnTypeNode;
+
+        return $node;
+    }
+
+    public function provideMinPhpVersion(): int
+    {
+        return PhpVersionFeature::ARROW_FUNCTION;
+    }
+}