reference previous #[TestWith] dataprovider by label

Author: staabm

src/Metadata/Api/DataProvider.php

@@ -231,19 +231,19 @@ private function dataProvidedByMetadata(MetadataCollection $testWith): array
     {
         $result = [];
 
-        $providerLabel = 'TestWith attribute';
-
-        foreach ($testWith as $_testWith) {
+        foreach ($testWith as $i => $_testWith) {
             assert($_testWith instanceof TestWith);
+            $providerLabel = sprintf('TestWith#%s attribute', $i);
 
             if ($_testWith->hasName()) {
                 $key = $_testWith->name();
 
                 if (array_key_exists($key, $result)) {
                     throw new InvalidDataProviderException(
                         sprintf(
-                            'The key "%s" has already been defined by a previous TestWith attribute',
+                            'The key "%s" has already been defined by %s',
                             $key,
+                            $result[$key]->getProviderLabel(),
                         ),
                     );
                 }

tests/unit/Metadata/Api/DataProviderTest.php

@@ -195,7 +195,7 @@ public function testTestWithAttribute(): void
     public function testTestWithAttributeWithDuplicateKey(): void
     {
         $this->expectException(InvalidDataProviderException::class);
-        $this->expectExceptionMessage('The key "foo" has already been defined by a previous TestWith attribute');
+        $this->expectExceptionMessage('The key "foo" has already been defined by TestWith#0 attribute');
 
         /* @noinspection UnusedFunctionResultInspection */
         (new DataProvider)->providedData(TestWithAttributeDataProviderTest::class, 'testWithDuplicateName');