Implement PDO statment's fetchColumn() and fetchObject() methods (#315)

This PR implements two additional PDO statement proxy methods:
- `PDOStatement::fetchColumn()`
- `PDOStatement::fetchObject()`

Both of these methods delegate the calls to the underlying SQLite
statement.

There are more PDO APIs to cover, but I had these in an in-progress
branch, and there is no need to hold it off.
Additional PDO API coverage will be done in subsequent PRs.

Author: JanJakes

tests/WP_PDO_MySQL_On_SQLite_PDO_API_Tests.php

@@ -2,6 +2,20 @@
 
 use PHPUnit\Framework\TestCase;
 
+// phpcs:disable Generic.Files.OneObjectStructurePerFile.MultipleFound
+class FetchObjectTestClass {
+	public $col1;
+	public $col2;
+	public $col3;
+	public $arg1;
+	public $arg2;
+
+	public function __construct( $arg1 = null, $arg2 = null ) {
+		$this->arg1 = $arg1;
+		$this->arg2 = $arg2;
+	}
+}
+
 class WP_PDO_MySQL_On_SQLite_PDO_API_Tests extends TestCase {
 	/** @var WP_PDO_MySQL_On_SQLite */
 	private $driver;
@@ -324,6 +338,106 @@ public function test_fetch( $query, $mode, $expected ): void {
 		}
 	}
 
+	public function test_fetch_column(): void {
+		$query = "
+			SELECT 1, 'abc', true
+			UNION ALL
+			SELECT 2, 'xyz', false
+			UNION ALL
+			SELECT 3, null, null
+		";
+
+		// Fetch first column (default).
+		$stmt = $this->driver->query( $query );
+		$this->assertSame( '1', $stmt->fetchColumn() );
+		$this->assertSame( '2', $stmt->fetchColumn() );
+		$this->assertSame( '3', $stmt->fetchColumn() );
+		$this->assertFalse( $stmt->fetchColumn() );
+
+		// Fetch second column.
+		$stmt = $this->driver->query( $query );
+		$this->assertSame( 'abc', $stmt->fetchColumn( 1 ) );
+		$this->assertSame( 'xyz', $stmt->fetchColumn( 1 ) );
+		$this->assertNull( $stmt->fetchColumn( 1 ) );
+		$this->assertFalse( $stmt->fetchColumn( 1 ) );
+
+		// Fetch third column.
+		$stmt = $this->driver->query( $query );
+		$this->assertSame( '1', $stmt->fetchColumn( 2 ) );
+		$this->assertSame( '0', $stmt->fetchColumn( 2 ) );
+		$this->assertNull( $stmt->fetchColumn( 2 ) );
+		$this->assertFalse( $stmt->fetchColumn( 2 ) );
+
+		// Fetch different columns across rows.
+		$stmt = $this->driver->query( $query );
+		$this->assertSame( '1', $stmt->fetchColumn( 0 ) );
+		$this->assertSame( 'xyz', $stmt->fetchColumn( 1 ) );
+		$this->assertNull( $stmt->fetchColumn( 2 ) );
+		$this->assertFalse( $stmt->fetchColumn() );
+	}
+
+	public function test_fetch_column_invalid_index(): void {
+		$stmt = $this->driver->query( "SELECT 1, 'abc', true" );
+
+		if ( PHP_VERSION_ID < 80000 ) {
+			$this->expectException( PDOException::class );
+			$this->expectExceptionMessage( 'Invalid column index' );
+		} else {
+			$this->expectException( ValueError::class );
+			$this->expectExceptionMessage( 'Invalid column index' );
+		}
+		$stmt->fetchColumn( 3 );
+	}
+
+	public function test_fetch_column_negative_index(): void {
+		$stmt = $this->driver->query( "SELECT 1, 'abc', true" );
+
+		if ( PHP_VERSION_ID < 80000 ) {
+			$this->expectException( PDOException::class );
+			$this->expectExceptionMessage( 'Invalid column index' );
+		} else {
+			$this->expectException( ValueError::class );
+			$this->expectExceptionMessage( 'Column index must be greater than or equal to 0' );
+		}
+		$stmt->fetchColumn( -1 );
+	}
+
+	public function test_fetch_obj(): void {
+		// No arguments (stdClass).
+		$stmt = $this->driver->query( "SELECT 1, 'abc', true" );
+		$this->assertEquals(
+			(object) array(
+				1      => '1',
+				'abc'  => 'abc',
+				'true' => true,
+			),
+			$stmt->fetchObject()
+		);
+		$this->assertFalse( $stmt->fetchObject() );
+
+		// Custom class.
+		$stmt   = $this->driver->query( "SELECT 1 AS col1, 'abc' AS col2, true AS col3" );
+		$result = $stmt->fetchObject( FetchObjectTestClass::class );
+		$this->assertInstanceOf( FetchObjectTestClass::class, $result );
+		$this->assertSame( '1', $result->col1 );
+		$this->assertSame( 'abc', $result->col2 );
+		$this->assertSame( '1', $result->col3 );
+		$this->assertNull( $result->arg1 );
+		$this->assertNull( $result->arg2 );
+		$this->assertFalse( $stmt->fetchObject( FetchObjectTestClass::class ) );
+
+		// Custom class with constructor arguments.
+		$stmt   = $this->driver->query( "SELECT 1 AS col1, 'abc' AS col2, true AS col3" );
+		$result = $stmt->fetchObject( FetchObjectTestClass::class, array( 'val1', 'val2' ) );
+		$this->assertInstanceOf( FetchObjectTestClass::class, $result );
+		$this->assertSame( '1', $result->col1 );
+		$this->assertSame( 'abc', $result->col2 );
+		$this->assertSame( '1', $result->col3 );
+		$this->assertSame( 'val1', $result->arg1 );
+		$this->assertSame( 'val2', $result->arg2 );
+		$this->assertFalse( $stmt->fetchObject( FetchObjectTestClass::class, array( 'val1', 'val2' ) ) );
+	}
+
 	public function test_attr_default_fetch_mode(): void {
 		$this->driver->setAttribute( PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_NUM );
 		$result = $this->driver->query( "SELECT 'a', 'b', 'c'" );

wp-includes/sqlite-ast/class-wp-pdo-proxy-statement.php

@@ -196,7 +196,7 @@ public function fetch(
 	 */
 	#[ReturnTypeWillChange]
 	public function fetchColumn( $column = 0 ) {
-		throw new RuntimeException( 'Not implemented' );
+		return $this->statement->fetchColumn( $column );
 	}
 
 	/**
@@ -208,7 +208,7 @@ public function fetchColumn( $column = 0 ) {
 	 */
 	#[ReturnTypeWillChange]
 	public function fetchObject( $class = 'stdClass', $constructorArgs = array() ) {
-		throw new RuntimeException( 'Not implemented' );
+		return $this->statement->fetchObject( $class, $constructorArgs );
 	}
 
 	/**