Fix USE statement, add tests

tests/WP_SQLite_Driver_Tests.php

@@ -9325,4 +9325,46 @@ function ( $name ) {
 		$this->assertEquals( 'information_schema', $result[0]->SCHEMA_NAME );
 		$this->assertEquals( 'wp_test_new', $result[1]->SCHEMA_NAME );
 	}
+
+	public function testDynamicDatabaseNameWithUseStatement(): void {
+		// Ensure "information_schema.tables" is empty.
+		$this->assertQuery( 'DROP TABLE _options, _dates' );
+		$result = $this->assertQuery( 'SELECT * FROM information_schema.tables' );
+		$this->assertCount( 0, $result );
+
+		// Create a "tables" table in the "wp" database.
+		$this->assertQuery( 'CREATE TABLE tables (id INT)' );
+		$this->assertQuery( 'INSERT INTO tables (id) VALUES (1), (2)' );
+
+		// Now, unqualified "tables" refers to the "wp.tables".
+		$result = $this->assertQuery( 'SELECT * FROM tables' );
+		$this->assertCount( 2, $result );
+		$this->assertEquals( array( (object) array( 'id' => '1' ), (object) array( 'id' => '2' ) ), $result );
+
+		// Qualified references should work as well.
+		$result = $this->assertQuery( 'SELECT * FROM wp.tables' );
+		$this->assertCount( 2, $result );
+		$this->assertEquals( array( (object) array( 'id' => '1' ), (object) array( 'id' => '2' ) ), $result );
+
+		$result = $this->assertQuery( 'SELECT * FROM information_schema.tables' );
+		$this->assertCount( 1, $result );
+		$this->assertEquals( 'tables', $result[0]->TABLE_NAME );
+
+		// Switch to the "information_schema" database.
+		$this->assertQuery( 'USE information_schema' );
+
+		// Now, unqualified "tables" refers to the "information_schema.tables".
+		$result = $this->assertQuery( 'SELECT * FROM tables' );
+		$this->assertCount( 1, $result );
+		$this->assertEquals( 'tables', $result[0]->TABLE_NAME );
+
+		// Qualified references should still work.
+		$result = $this->assertQuery( 'SELECT * FROM wp.tables' );
+		$this->assertCount( 2, $result );
+		$this->assertEquals( array( (object) array( 'id' => '1' ), (object) array( 'id' => '2' ) ), $result );
+
+		$result = $this->assertQuery( 'SELECT * FROM information_schema.tables' );
+		$this->assertCount( 1, $result );
+		$this->assertEquals( 'tables', $result[0]->TABLE_NAME );
+	}
 }

wp-includes/sqlite-ast/class-wp-sqlite-driver.php

@@ -3353,7 +3353,7 @@ private function translate_qualified_identifier(
 			);
 			if ( 'information_schema' === strtolower( $schema_name ) ) {
 				$is_information_schema = true;
-			} elseif ( $this->db_name === $schema_name ) {
+			} elseif ( $this->main_db_name === $schema_name ) {
 				$is_information_schema = false;
 			} else {
 				throw $this->new_not_supported_exception(