[Configuration] Resolve --only rule name with shell-eaten backslashes

src/Configuration/OnlyRuleResolver.php

@@ -63,6 +63,19 @@ public function resolve(string $rule): string
         }
 
         if (! str_contains($rule, '\\')) {
+            // the shell has eaten unescaped backslashes, e.g. --only=\Rector\Some\Rule
+            $flattenMatching = [];
+            foreach ($this->rectors as $rector) {
+                if (str_replace('\\', '', $rector::class) === $rule) {
+                    $flattenMatching[] = $rector::class;
+                }
+            }
+
+            $flattenMatching = array_unique($flattenMatching);
+            if (count($flattenMatching) === 1) {
+                return $flattenMatching[0];
+            }
+
             $message = sprintf(
                 'Rule "%s" was not found.%sThe rule has no namespace. Make sure to escape the backslashes, and add quotes around the rule name: --only="My\\Rector\\Rule"',
                 $rule,

tests/Configuration/OnlyRuleResolverTest.php

@@ -63,14 +63,23 @@ public function testResolveOkSingleQuotes(): void
     }
 
     public function testResolveMissingBackslash(): void
+    {
+        $this->assertSame(
+            RemoveDoubleAssignRector::class,
+            $this->onlyRuleResolver->resolve('RectorDeadCodeRectorAssignRemoveDoubleAssignRector'),
+            'The shell eats unescaped backslashes, resolve the flattened rule name anyway'
+        );
+    }
+
+    public function testResolveMissingBackslashNotFound(): void
     {
         $this->expectExceptionMessageIsOrContains(
-            'Rule "RectorDeadCodeRectorAssignRemoveDoubleAssignRector" was not found.' . PHP_EOL
+            'Rule "ThisRuleDoesNotExist" was not found.' . PHP_EOL
                 . 'The rule has no namespace. Make sure to escape the backslashes, and add quotes around the rule name: --only="My\\Rector\\Rule"'
         );
         $this->expectException(RectorRuleNotFoundException::class);
 
-        $this->onlyRuleResolver->resolve('RectorDeadCodeRectorAssignRemoveDoubleAssignRector');
+        $this->onlyRuleResolver->resolve('ThisRuleDoesNotExist');
     }
 
     public function testResolveNotFound(): void