Handled tag conflict from rename tag action

module/Core/src/Exception/TagConflictException.php

@@ -8,8 +8,8 @@ use function sprintf;
 
 class TagConflictException extends RuntimeException
 {
-    public static function fromExistingTag(string $tag): self
+    public static function fromExistingTag(string $oldName, string $newName): self
     {
-        return new self(sprintf('Tag with name %s already exists', $tag));
+        return new self(sprintf('You cannot rename tag %s to %s, because it already exists', $oldName, $newName));
     }
 }

module/Core/src/Service/Tag/TagService.php

@@ -82,7 +82,7 @@ class TagService implements TagServiceInterface
 
         $newNameExists = $newName !== $oldName && $repo->count(['name' => $newName]) > 0;
         if ($newNameExists) {
-            throw TagConflictException::fromExistingTag($newName);
+            throw TagConflictException::fromExistingTag($oldName, $newName);
         }
 
         $tag->rename($newName);

module/Rest/src/Action/Tag/UpdateTagAction.php

@@ -8,6 +8,7 @@ use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Log\LoggerInterface;
 use Shlinkio\Shlink\Core\Exception\EntityDoesNotExistException;
+use Shlinkio\Shlink\Core\Exception\TagConflictException;
 use Shlinkio\Shlink\Core\Service\Tag\TagServiceInterface;
 use Shlinkio\Shlink\Rest\Action\AbstractRestAction;
 use Shlinkio\Shlink\Rest\Util\RestUtils;
@@ -58,6 +59,15 @@ class UpdateTagAction extends AbstractRestAction
                 'error' => RestUtils::NOT_FOUND_ERROR,
                 'message' => sprintf('It was not possible to find a tag with name %s', $body['oldName']),
             ], self::STATUS_NOT_FOUND);
+        } catch (TagConflictException $e) {
+            return new JsonResponse([
+                'error' => 'TAG_CONFLICT',
+                'message' => sprintf(
+                    'You cannot rename tag %s to %s, because it already exists',
+                    $body['oldName'],
+                    $body['newName']
+                ),
+            ], self::STATUS_CONFLICT);
         }
     }
 }

module/Rest/test-api/Action/UpdateTagActionTest.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioApiTest\Shlink\Rest\Action;
+
+use GuzzleHttp\RequestOptions;
+use Shlinkio\Shlink\TestUtils\ApiTest\ApiTestCase;
+
+class UpdateTagActionTest extends ApiTestCase
+{
+    /** @test */
+    public function errorIsThrownWhenTryingToRenameTagToAnotherTagName(): void
+    {
+        $resp = $this->callApiWithKey(self::METHOD_PUT, '/tags', [RequestOptions::JSON => [
+            'oldName' => 'foo',
+            'newName' => 'bar',
+        ]]);
+        $payload = $this->getJsonResponsePayload($resp);
+
+        $this->assertEquals(self::STATUS_CONFLICT, $resp->getStatusCode());
+        $this->assertEquals('TAG_CONFLICT', $payload['error']);
+    }
+
+    /** @test */
+    public function tagIsProperlyRenamedWhenRenamingToItself(): void
+    {
+        $resp = $this->callApiWithKey(self::METHOD_PUT, '/tags', [RequestOptions::JSON => [
+            'oldName' => 'foo',
+            'newName' => 'foo',
+        ]]);
+
+        $this->assertEquals(self::STATUS_NO_CONTENT, $resp->getStatusCode());
+    }
+}