ResultSet: improved error message on duplicated names in select statement

Author: Unlink

src/Database/Helpers.php

@@ -266,4 +266,27 @@ public static function toPairs(array $rows, $key = NULL, $value = NULL)
 		return $return;
 	}
 
+
+	/**
+	 * Finds duplicate columns in select statement
+	 * @param  \PDOStatement
+	 * @return string
+	 */
+	public static function findDuplicates(\PDOStatement $statement)
+	{
+		$cols = [];
+		for ($i = 0; $i < $statement->columnCount(); $i++) {
+			$meta = $statement->getColumnMeta($i);
+			$cols[$meta['name']][] = isset($meta['table']) ? $meta['table'] : '';
+		}
+		$duplicates = [];
+		foreach ($cols as $name => $tables) {
+			if (count($tables) > 1) {
+				$tables = array_filter(array_unique($tables));
+				$duplicates[] = "'$name'" . ($tables ? ' (from ' . implode(', ', $tables) . ')' : '');
+			}
+		}
+		return implode(', ', $duplicates);
+	}
+
 }

src/Database/ResultSet.php

@@ -253,6 +253,10 @@ public function fetch()
 		if (!$data) {
 			$this->pdoStatement->closeCursor();
 			return FALSE;
+
+		} elseif ($this->result === NULL && count($data) !== $this->pdoStatement->columnCount()) {
+			$duplicates = Helpers::findDuplicates($this->pdoStatement);
+			trigger_error("Found duplicate columns in database result set: $duplicates.", E_USER_NOTICE);
 		}
 
 		$row = new Row;
@@ -262,10 +266,6 @@ public function fetch()
 			}
 		}
 
-		if ($this->result === NULL && count($data) !== $this->pdoStatement->columnCount()) {
-			trigger_error('Found duplicate columns in database result set.', E_USER_NOTICE);
-		}
-
 		$this->resultKey++;
 		return $this->result = $row;
 	}

tests/Database/ResultSet.fetch().phpt

@@ -12,12 +12,27 @@ require __DIR__ . '/connect.inc.php'; // create $connection
 Nette\Database\Helpers::loadFromFile($connection, __DIR__ . "/files/{$driverName}-nette_test1.sql");
 
 
-test(function () use ($context) {
+test(function () use ($context, $driverName) {
 	$res = $context->query('SELECT name, name FROM author');
-
+	switch ($driverName) {
+		case 'mysql':
+			$message = "Found duplicate columns in database result set: 'name' (from author).";
+			break;
+		case 'pgsql':
+			$message = "Found duplicate columns in database result set: 'name'%a%";
+			break;
+		case 'sqlite':
+			$message = "Found duplicate columns in database result set: 'name' (from author).";
+			break;
+		case 'sqlsrv':
+			$message = "Found duplicate columns in database result set: 'name'.";
+			break;
+		default:
+			Assert::fail("Unsupported driver $driverName");
+	}
 	Assert::error(function () use ($res) {
 		$res->fetch();
-	}, E_USER_NOTICE, 'Found duplicate columns in database result set.');
+	}, E_USER_NOTICE, $message);
 
 	$res->fetch();
 });
@@ -35,3 +50,27 @@ test(function () use ($context, $driverName) { // tests closeCursor()
 		foreach ($res as $row) {}
 	}
 });
+
+
+test(function () use ($context, $driverName) {
+	$res = $context->query('SELECT book.id, author.id, author.name, translator.name FROM book JOIN author ON (author.id = book.author_id) JOIN author translator ON (translator.id = book.translator_id)');
+	switch ($driverName) {
+		case 'mysql':
+			$message = "Found duplicate columns in database result set: 'id' (from book, author), 'name' (from author, translator).";
+			break;
+		case 'pgsql':
+			$message = "Found duplicate columns in database result set: 'id'%a% 'name'%a%";
+			break;
+		case 'sqlite':
+			$message = "Found duplicate columns in database result set: 'id' (from book, author), 'name' (from author).";
+			break;
+		case 'sqlsrv':
+			$message = "Found duplicate columns in database result set: 'id', 'name'.";
+			break;
+		default:
+			Assert::fail("Unsupported driver $driverName");
+	}
+	Assert::error(function() use ($res) {
+		$res->fetch();
+	}, E_USER_NOTICE, $message);
+});