#6 implemented MethodVisibilityReduced comparator

src/Comparator/BackwardsCompatibility/ClassBased/MethodVisibilityReduced.php

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+<?php
+
+declare(strict_types=1);
+
+namespace Roave\ApiCompare\Comparator\BackwardsCompatibility\ClassBased;
+
+use Assert\Assert;
+use Roave\ApiCompare\Change;
+use Roave\ApiCompare\Changes;
+use Roave\BetterReflection\Reflection\ReflectionClass;
+use Roave\BetterReflection\Reflection\ReflectionMethod;
+
+final class MethodVisibilityReduced implements ClassBased
+{
+    private const VISIBILITY_PRIVATE = 'private';
+
+    private const VISIBILITY_PROTECTED = 'protected';
+
+    private const VISIBILITY_PUBLIC = 'public';
+
+    public function compare(ReflectionClass $fromClass, ReflectionClass $toClass) : Changes
+    {
+        Assert::that($fromClass->getName())->same($toClass->getName());
+
+        $visibilitiesFrom = $this->methodVisibilities($fromClass);
+        $visibilitiesTo   = $this->methodVisibilities($toClass);
+
+        $affectedVisibilities = array_filter(
+            array_combine(
+                array_keys(array_intersect_key($visibilitiesFrom, $visibilitiesTo)),
+                array_map(
+                    function (string $visibilityFrom, string $visibilityTo) : array {
+                        return [$visibilityFrom, $visibilityTo];
+                    },
+                    array_intersect_key($visibilitiesFrom, $visibilitiesTo),
+                    array_intersect_key($visibilitiesTo, $visibilitiesFrom)
+                )
+            ),
+            function (array $visibilities) : bool {
+                // Note: works because public, protected and private are (luckily) sortable
+                return $visibilities[0] > $visibilities[1];
+            }
+        );
+
+        return Changes::fromArray(array_values(array_map(function (string $methodName, array $visibilities) use (
+            $fromClass
+        ) : Change {
+            return Change::changed(
+                sprintf(
+                    'Method %s#%s() changed visibility from %s to %s',
+                    $fromClass->getName(),
+                    $fromClass->getMethod($methodName)->getName(),
+                    $visibilities[0],
+                    $visibilities[1]
+                ),
+                true
+            );
+        }, array_keys($affectedVisibilities), $affectedVisibilities)));
+    }
+
+    /** @return string[] */
+    private function methodVisibilities(ReflectionClass $class) : array
+    {
+        $methods = $class->getMethods();
+
+        return array_combine(
+            array_map(function (ReflectionMethod $method) : string {
+                return $method->getName();
+            }, $methods),
+            array_map(function (ReflectionMethod $method) : string {
+                if ($method->isPublic()) {
+                    return self::VISIBILITY_PUBLIC;
+                }
+
+                if ($method->isProtected()) {
+                    return self::VISIBILITY_PROTECTED;
+                }
+
+                return self::VISIBILITY_PRIVATE;
+            }, $methods)
+        );
+    }
+}

test/asset/api/new/ClassWithMethodVisibilitiesBeingChanged.php

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+<?php
+declare(strict_types=1);
+
+namespace RoaveTestAsset;
+
+class ClassWithMethodVisibilitiesBeingChanged
+{
+    public function publicMaintainedPublic()
+    {
+    }
+    protected function publicReducedToProtected()
+    {
+    }
+    private function publicReducedToPrivate()
+    {
+    }
+    protected function protectedMaintainedProtected()
+    {
+    }
+    private function protectedReducedToPrivate()
+    {
+    }
+    public function protectedIncreasedToPublic()
+    {
+    }
+    private function privateMaintainedPrivate()
+    {
+    }
+    protected function privateIncreasedToProtected()
+    {
+    }
+    public function privateIncreasedToPublic()
+    {
+    }
+}

test/asset/api/old/ClassWithMethodVisibilitiesBeingChanged.php

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+<?php
+declare(strict_types=1);
+
+namespace RoaveTestAsset;
+
+class ClassWithMethodVisibilitiesBeingChanged
+{
+    public function publicMaintainedPublic()
+    {
+    }
+    public function publicReducedToProtected()
+    {
+    }
+    public function publicReducedToPrivate()
+    {
+    }
+    protected function protectedMaintainedProtected()
+    {
+    }
+    protected function protectedReducedToPrivate()
+    {
+    }
+    protected function protectedIncreasedToPublic()
+    {
+    }
+    private function privateMaintainedPrivate()
+    {
+    }
+    private function privateIncreasedToProtected()
+    {
+    }
+    private function privateIncreasedToPublic()
+    {
+    }
+}

test/unit/Comparator/BackwardsCompatibility/ClassBased/MethodVisibilityReducedTest.php

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+<?php
+
+declare(strict_types=1);
+
+namespace RoaveTest\ApiCompare\Comparator\BackwardsCompatibility\ClassBased;
+
+use PHPUnit\Framework\TestCase;
+use Roave\ApiCompare\Change;
+use Roave\ApiCompare\Comparator\BackwardsCompatibility\ClassBased\MethodVisibilityReduced;
+use Roave\ApiCompare\Comparator\BackwardsCompatibility\ClassBased\PropertyVisibilityReduced;
+use Roave\BetterReflection\BetterReflection;
+use Roave\BetterReflection\Reflection\ReflectionClass;
+use Roave\BetterReflection\Reflector\ClassReflector;
+use Roave\BetterReflection\SourceLocator\Type\SingleFileSourceLocator;
+
+final class MethodVisibilityReducedTest extends TestCase
+{
+    /**
+     * @dataProvider classesToBeTested
+     *
+     * @param string[] $expectedMessages
+     */
+    public function testDiffs(
+        ReflectionClass $fromClass,
+        ReflectionClass $toClass,
+        array $expectedMessages
+    ) : void {
+        $changes = (new MethodVisibilityReduced())
+            ->compare($fromClass, $toClass);
+
+        self::assertSame(
+            $expectedMessages,
+            array_map(function (Change $change) : string {
+                return $change->__toString();
+            }, iterator_to_array($changes))
+        );
+    }
+
+    /** @return (string[]|ReflectionClass)[][] */
+    public function classesToBeTested() : array
+    {
+        $locator = (new BetterReflection())->astLocator();
+
+        return [
+            'RoaveTestAsset\\ClassWithPropertyVisibilitiesBeingChanged' => [
+                (new ClassReflector(new SingleFileSourceLocator(
+                    __DIR__ . '/../../../../asset/api/old/ClassWithMethodVisibilitiesBeingChanged.php',
+                    $locator
+                )))->reflect('RoaveTestAsset\\ClassWithMethodVisibilitiesBeingChanged'),
+                (new ClassReflector(new SingleFileSourceLocator(
+                    __DIR__ . '/../../../../asset/api/new/ClassWithMethodVisibilitiesBeingChanged.php',
+                    $locator
+                )))->reflect('RoaveTestAsset\\ClassWithMethodVisibilitiesBeingChanged'),
+                [
+                    '[BC] CHANGED: Method RoaveTestAsset\ClassWithMethodVisibilitiesBeingChanged#publicReducedToProtected() changed visibility from public to protected',
+                    '[BC] CHANGED: Method RoaveTestAsset\ClassWithMethodVisibilitiesBeingChanged#publicReducedToPrivate() changed visibility from public to private',
+                    '[BC] CHANGED: Method RoaveTestAsset\ClassWithMethodVisibilitiesBeingChanged#protectedReducedToPrivate() changed visibility from protected to private',
+                ],
+            ],
+        ];
+    }
+}