Downgrade arrow functions (#4137)

* Extracted rule into abstract class for reuse

* Implemented rule

* Added rule to downgrade set

* Fixed rector-ci errors

* Fixed cs

* Preserve return type

* Direct assignment of parameters

* Use interface instead of abstract methods

* Moved abstract class under Php72

* Added test for params with type

config/set/downgrade.php

@@ -2,6 +2,7 @@
 
 declare(strict_types=1);
 
+use Rector\Downgrade\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector;
 use Rector\Downgrade\Rector\Coalesce\DowngradeNullCoalescingOperatorRector;
 use Rector\Downgrade\Rector\FunctionLike\DowngradeParamObjectTypeDeclarationRector;
 use Rector\Downgrade\Rector\FunctionLike\DowngradeReturnObjectTypeDeclarationRector;
@@ -17,5 +18,7 @@ return static function (ContainerConfigurator $containerConfigurator): void {
 
     $services->set(DowngradeTypedPropertyRector::class);
 
+    $services->set(ArrowFunctionToAnonymousFunctionRector::class);
+
     $services->set(DowngradeNullCoalescingOperatorRector::class);
 };

rules/downgrade/src/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector.php

@@ -0,0 +1,99 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Downgrade\Rector\ArrowFunction;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\ArrowFunction;
+use PhpParser\Node\Identifier;
+use PhpParser\Node\Name;
+use PhpParser\Node\NullableType;
+use PhpParser\Node\Param;
+use PhpParser\Node\Stmt\Return_;
+use PhpParser\Node\UnionType;
+use Rector\Core\RectorDefinition\CodeSample;
+use Rector\Core\RectorDefinition\RectorDefinition;
+use Rector\Php72\Rector\FuncCall\AbstractConvertToAnonymousFunctionRector;
+
+/**
+ * @see https://www.php.net/manual/en/functions.arrow.php
+ *
+ * @see \Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\ArrowFunctionToAnonymousFunctionRectorTest
+ */
+final class ArrowFunctionToAnonymousFunctionRector extends AbstractConvertToAnonymousFunctionRector
+{
+    public function getDefinition(): RectorDefinition
+    {
+        return new RectorDefinition('Replace arrow functions with anonymous functions', [
+            new CodeSample(
+                <<<'PHP'
+class SomeClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = fn($matches) => $delimiter . strtolower($matches[1]);
+    }
+}
+PHP
+                ,
+                <<<'PHP'
+class SomeClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = function ($matches) use ($delimiter) {
+            return $delimiter . strtolower($matches[1]);
+        };
+    }
+}
+PHP
+            ),
+        ]);
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getNodeTypes(): array
+    {
+        return [ArrowFunction::class];
+    }
+
+    /**
+     * @param ArrowFunction $node
+     */
+    public function shouldSkip(Node $node): bool
+    {
+        return false;
+    }
+
+    /**
+     * @param ArrowFunction $node
+     * @return Param[]
+     */
+    public function getParameters(Node $node): array
+    {
+        return $node->params;
+    }
+
+    /**
+     * @param ArrowFunction $node
+     * @return Identifier|Name|NullableType|UnionType|null
+     */
+    public function getReturnType(Node $node): ?Node
+    {
+        return $node->returnType;
+    }
+
+    /**
+     * @param ArrowFunction $node
+     * @return Return_[]
+     */
+    public function getBody(Node $node): array
+    {
+        return [new Return_($node->expr)];
+    }
+}

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/ArrowFunctionToAnonymousFunctionRectorTest.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector;
+
+use Iterator;
+use Rector\Core\Testing\PHPUnit\AbstractRectorTestCase;
+use Rector\Core\ValueObject\PhpVersionFeature;
+use Rector\Downgrade\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector;
+use Symplify\SmartFileSystem\SmartFileInfo;
+
+final class ArrowFunctionToAnonymousFunctionRectorTest extends AbstractRectorTestCase
+{
+    /**
+     * @requires PHP >= 7.4
+     * @dataProvider provideData()
+     */
+    public function test(SmartFileInfo $fileInfo): void
+    {
+        $this->doTestFileInfo($fileInfo);
+    }
+
+    public function provideData(): Iterator
+    {
+        return $this->yieldFilesFromDirectory(__DIR__ . '/Fixture');
+    }
+
+    protected function getRectorClass(): string
+    {
+        return ArrowFunctionToAnonymousFunctionRector::class;
+    }
+
+    protected function getPhpVersion(): string
+    {
+        return PhpVersionFeature::BEFORE_ARROW_FUNCTION;
+    }
+}

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/fixture.php.inc

@@ -0,0 +1,31 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class FixtureClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = fn($matches) => $delimiter . strtolower($matches[1]);
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class FixtureClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = function ($matches) use ($delimiter) {
+            return $delimiter . strtolower($matches[1]);
+        };
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/no_params.php.inc

@@ -0,0 +1,31 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoParamsClass
+{
+    public function run()
+    {
+        $delimiter = " ";
+        $callable = fn() => 'Hello' . $delimiter . 'world';
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoParamsClass
+{
+    public function run()
+    {
+        $delimiter = " ";
+        $callable = function () use ($delimiter) {
+            return 'Hello' . $delimiter . 'world';
+        };
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/no_params_or_use.php.inc

@@ -0,0 +1,29 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoParamsOrUseClass
+{
+    public function run()
+    {
+        $callable = fn() => 'Hello world';
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoParamsOrUseClass
+{
+    public function run()
+    {
+        $callable = function () {
+            return 'Hello world';
+        };
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/no_use.php.inc

@@ -0,0 +1,31 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoUseClass
+{
+    public function duplicate()
+    {
+        $numbers = [3, 5, 7];
+        return array_map(fn(int $number) => $number * 2, $numbers);
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNoUseClass
+{
+    public function duplicate()
+    {
+        $numbers = [3, 5, 7];
+        return array_map(function (int $number) {
+            return $number * 2;
+        }, $numbers);
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/params_with_type.php.inc

@@ -0,0 +1,31 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class ParamsWithTypeClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = fn(array $matches) => $delimiter . strtolower($matches[1]);
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class ParamsWithTypeClass
+{
+    public function run()
+    {
+        $delimiter = ",";
+        $callable = function (array $matches) use ($delimiter) {
+            return $delimiter . strtolower($matches[1]);
+        };
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/with_nullable_return_type.php.inc

@@ -0,0 +1,29 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNullableReturnTypeClass
+{
+    public function run()
+    {
+        $callable = fn(): ?string => 'Hello world';
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithNullableReturnTypeClass
+{
+    public function run()
+    {
+        $callable = function () : ?string {
+            return 'Hello world';
+        };
+    }
+}
+
+?>

rules/downgrade/tests/Rector/ArrowFunction/ArrowFunctionToAnonymousFunctionRector/Fixture/with_return_type.php.inc

@@ -0,0 +1,29 @@
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithReturnTypeClass
+{
+    public function run()
+    {
+        $callable = fn(): string => 'Hello world';
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Downgrade\Tests\Rector\ArrowFunction\ArrowFunctionToAnonymousFunctionRector\Fixture;
+
+class WithReturnTypeClass
+{
+    public function run()
+    {
+        $callable = function () : string {
+            return 'Hello world';
+        };
+    }
+}
+
+?>

rules/php72/src/Contract/ConvertToAnonymousFunctionRectorInterface.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Php72\Contract;
+
+use PhpParser\Node;
+use PhpParser\Node\Identifier;
+use PhpParser\Node\Name;
+use PhpParser\Node\NullableType;
+use PhpParser\Node\Param;
+use PhpParser\Node\Stmt;
+use PhpParser\Node\Stmt\Expression;
+use PhpParser\Node\UnionType;
+
+interface ConvertToAnonymousFunctionRectorInterface
+{
+    public function shouldSkip(Node $node): bool;
+
+    /**
+     * @return Param[]
+     */
+    public function getParameters(Node $node): array;
+
+    /**
+     * @return Identifier|Name|NullableType|UnionType|null
+     */
+    public function getReturnType(Node $node): ?Node;
+
+    /**
+     * @return Expression[]|Stmt[]
+     */
+    public function getBody(Node $node): array;
+}

rules/php72/src/Rector/FuncCall/AbstractConvertToAnonymousFunctionRector.php

@@ -0,0 +1,94 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Php72\Rector\FuncCall;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\Assign;
+use PhpParser\Node\Expr\Closure;
+use PhpParser\Node\Expr\ClosureUse;
+use PhpParser\Node\Expr\Variable;
+use PhpParser\Node\Param;
+use Rector\Core\Rector\AbstractRector;
+use Rector\NodeTypeResolver\Node\AttributeKey;
+use Rector\Php72\Contract\ConvertToAnonymousFunctionRectorInterface;
+
+/**
+ * @see https://www.php.net/functions.anonymous
+ */
+abstract class AbstractConvertToAnonymousFunctionRector extends AbstractRector implements ConvertToAnonymousFunctionRectorInterface
+{
+    public function refactor(Node $node): ?Node
+    {
+        if ($this->shouldSkip($node)) {
+            return null;
+        }
+
+        $body = $this->getBody($node);
+        $parameters = $this->getParameters($node);
+        $useVariables = $this->resolveUseVariables($body, $parameters);
+
+        $anonymousFunctionNode = new Closure();
+        $anonymousFunctionNode->params = $parameters;
+
+        foreach ($useVariables as $useVariable) {
+            $anonymousFunctionNode->uses[] = new ClosureUse($useVariable);
+        }
+
+        $anonymousFunctionNode->returnType = $this->getReturnType($node);
+
+        if ($body !== []) {
+            $anonymousFunctionNode->stmts = $body;
+        }
+
+        return $anonymousFunctionNode;
+    }
+
+    /**
+     * @param Node[] $nodes
+     * @param Param[] $paramNodes
+     * @return Variable[]
+     */
+    private function resolveUseVariables(array $nodes, array $paramNodes): array
+    {
+        $paramNames = [];
+        foreach ($paramNodes as $paramNode) {
+            $paramNames[] = $this->getName($paramNode);
+        }
+
+        $variableNodes = $this->betterNodeFinder->findInstanceOf($nodes, Variable::class);
+
+        /** @var Variable[] $filteredVariables */
+        $filteredVariables = [];
+        $alreadyAssignedVariables = [];
+        foreach ($variableNodes as $variableNode) {
+            // "$this" is allowed
+            if ($this->isName($variableNode, 'this')) {
+                continue;
+            }
+
+            $variableName = $this->getName($variableNode);
+            if ($variableName === null) {
+                continue;
+            }
+
+            if (in_array($variableName, $paramNames, true)) {
+                continue;
+            }
+
+            $parentNode = $variableNode->getAttribute(AttributeKey::PARENT_NODE);
+            if ($parentNode instanceof Assign) {
+                $alreadyAssignedVariables[] = $variableName;
+            }
+
+            if ($this->isNames($variableNode, $alreadyAssignedVariables)) {
+                continue;
+            }
+
+            $filteredVariables[$variableName] = $variableNode;
+        }
+
+        return $filteredVariables;
+    }
+}

rules/php72/src/Rector/FuncCall/CreateFunctionToAnonymousFunctionRector.php

@@ -10,21 +10,20 @@ use PhpParser\Node\Expr;
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\BinaryOp\Concat;
 use PhpParser\Node\Expr\Closure;
-use PhpParser\Node\Expr\ClosureUse;
 use PhpParser\Node\Expr\FuncCall;
-use PhpParser\Node\Expr\Variable;
+use PhpParser\Node\Identifier;
 use PhpParser\Node\Name;
+use PhpParser\Node\NullableType;
 use PhpParser\Node\Param;
 use PhpParser\Node\Scalar\Encapsed;
 use PhpParser\Node\Scalar\String_;
 use PhpParser\Node\Stmt;
 use PhpParser\Node\Stmt\Expression;
+use PhpParser\Node\UnionType;
 use Rector\Core\Exception\ShouldNotHappenException;
 use Rector\Core\PhpParser\Parser\InlineCodeParser;
-use Rector\Core\Rector\AbstractRector;
 use Rector\Core\RectorDefinition\CodeSample;
 use Rector\Core\RectorDefinition\RectorDefinition;
-use Rector\NodeTypeResolver\Node\AttributeKey;
 
 /**
  * @see https://stackoverflow.com/q/48161526/1348344
@@ -32,7 +31,7 @@ use Rector\NodeTypeResolver\Node\AttributeKey;
  *
  * @see \Rector\Php72\Tests\Rector\FuncCall\CreateFunctionToAnonymousFunctionRector\CreateFunctionToAnonymousFunctionRectorTest
  */
-final class CreateFunctionToAnonymousFunctionRector extends AbstractRector
+final class CreateFunctionToAnonymousFunctionRector extends AbstractConvertToAnonymousFunctionRector
 {
     /**
      * @var InlineCodeParser
@@ -84,33 +83,35 @@ PHP
     /**
      * @param FuncCall $node
      */
-    public function refactor(Node $node): ?Node
+    public function shouldSkip(Node $node): bool
     {
-        if (! $this->isName($node, 'create_function')) {
-            return null;
-        }
+        return ! $this->isName($node, 'create_function');
+    }
 
-        /** @var Variable[] $parameters */
-        $parameters = $this->parseStringToParameters($node->args[0]->value);
-        $body = $this->parseStringToBody($node->args[1]->value);
-        $useVariables = $this->resolveUseVariables($body, $parameters);
+    /**
+     * @param FuncCall $node
+     * @return Param[]
+     */
+    public function getParameters(Node $node): array
+    {
+        return $this->parseStringToParameters($node->args[0]->value);
+    }
 
-        $anonymousFunctionNode = new Closure();
+    /**
+     * @return Identifier|Name|NullableType|UnionType|null
+     */
+    public function getReturnType(Node $node): ?Node
+    {
+        return null;
+    }
 
-        foreach ($parameters as $parameter) {
-            /** @var Variable $parameter */
-            $anonymousFunctionNode->params[] = new Param($parameter);
-        }
-
-        if ($body !== []) {
-            $anonymousFunctionNode->stmts = $body;
-        }
-
-        foreach ($useVariables as $useVariable) {
-            $anonymousFunctionNode->uses[] = new ClosureUse($useVariable);
-        }
-
-        return $anonymousFunctionNode;
+    /**
+     * @param FuncCall $node
+     * @return Stmt[]
+     */
+    public function getBody(Node $node): array
+    {
+        return $this->parseStringToBody($node->args[1]->value);
     }
 
     /**
@@ -153,53 +154,6 @@ PHP
         return $this->inlineCodeParser->parse($node);
     }
 
-    /**
-     * @param Node[] $nodes
-     * @param Variable[] $paramNodes
-     * @return Variable[]
-     */
-    private function resolveUseVariables(array $nodes, array $paramNodes): array
-    {
-        $paramNames = [];
-        foreach ($paramNodes as $paramNode) {
-            $paramNames[] = $this->getName($paramNode);
-        }
-
-        $variableNodes = $this->betterNodeFinder->findInstanceOf($nodes, Variable::class);
-
-        /** @var Variable[] $filteredVariables */
-        $filteredVariables = [];
-        $alreadyAssignedVariables = [];
-        foreach ($variableNodes as $variableNode) {
-            // "$this" is allowed
-            if ($this->isName($variableNode, 'this')) {
-                continue;
-            }
-
-            $variableName = $this->getName($variableNode);
-            if ($variableName === null) {
-                continue;
-            }
-
-            if (in_array($variableName, $paramNames, true)) {
-                continue;
-            }
-
-            $parentNode = $variableNode->getAttribute(AttributeKey::PARENT_NODE);
-            if ($parentNode instanceof Assign) {
-                $alreadyAssignedVariables[] = $variableName;
-            }
-
-            if ($this->isNames($variableNode, $alreadyAssignedVariables)) {
-                continue;
-            }
-
-            $filteredVariables[$variableName] = $variableNode;
-        }
-
-        return $filteredVariables;
-    }
-
     private function createEval(Expr $expr): Expression
     {
         $evalFuncCall = new FuncCall(new Name('eval'), [new Arg($expr)]);

src/ValueObject/PhpVersionFeature.php

@@ -146,6 +146,11 @@ final class PhpVersionFeature
      */
     public const BEFORE_TYPED_PROPERTIES = '7.3';
 
+    /**
+     * @var string
+     */
+    public const BEFORE_ARROW_FUNCTION = '7.3';
+
     /**
      * @var string
      */