Implement altering column with SET DEFAULT and DROP DEFAULT

Author: JanJakes

tests/WP_SQLite_Translator_Tests.php

@@ -3048,6 +3048,63 @@ public function testCurrentTimestamp() {
 		$this->assertQuery( 'DELETE FROM _dates WHERE option_value = CURRENT_TIMESTAMP()' );
 	}
 
+
+	public function testAlterColumnSetAndDropDefault() {
+		$this->assertQuery(
+			'CREATE TABLE _tmp_table (
+				name varchar(20) NOT NULL
+			);'
+		);
+		$result = $this->assertQuery( 'DESCRIBE _tmp_table' );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'Field'   => 'name',
+					'Type'    => 'varchar(20)',
+					'Null'    => 'NO',
+					'Key'     => '',
+					'Default' => '',
+					'Extra'   => '',
+				),
+			),
+			$result
+		);
+
+		// SET DEFAULT
+		$this->assertQuery( "ALTER TABLE _tmp_table CHANGE name SET DEFAULT 'abc'" );
+		$result = $this->assertQuery( 'DESCRIBE _tmp_table' );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'Field'   => 'name',
+					'Type'    => 'varchar(20)',
+					'Null'    => 'NO',
+					'Key'     => '',
+					'Default' => 'abc',
+					'Extra'   => '',
+				),
+			),
+			$result
+		);
+
+		// DROP DEFAULT
+		$this->assertQuery( 'ALTER TABLE _tmp_table CHANGE name DROP DEFAULT' );
+		$result = $this->assertQuery( 'DESCRIBE _tmp_table' );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'Field'   => 'name',
+					'Type'    => 'varchar(20)',
+					'Null'    => 'NO',
+					'Key'     => '',
+					'Default' => '',
+					'Extra'   => '',
+				),
+			),
+			$result
+		);
+	}
+
 	/**
 	 * @dataProvider mysqlVariablesToTest
 	 */

wp-includes/sqlite/class-wp-sqlite-translator.php

@@ -3053,16 +3053,31 @@ private function execute_alter() {
 				$this->rewriter->consume_all();
 			} elseif ( 'CHANGE' === $op_type ) {
 				// Parse the new column definition.
-				$raw_from_name    = 'COLUMN' === $op_subject ? $this->rewriter->skip()->token : $op_raw_subject;
-				$from_name        = $this->normalize_column_name( $raw_from_name );
-				$new_field        = $this->parse_mysql_create_table_field();
-				$alter_terminator = end( $this->rewriter->output_tokens );
-				$this->update_data_type_cache(
-					$this->table_name,
-					$new_field->name,
-					$new_field->mysql_data_type
+				$raw_from_name = 'COLUMN' === $op_subject ? $this->rewriter->skip()->token : $op_raw_subject;
+				$from_name     = $this->normalize_column_name( $raw_from_name );
+
+				$set_or_drop_default = $this->rewriter->peek()->matches(
+					WP_SQLite_Token::TYPE_KEYWORD,
+					WP_SQLite_Token::FLAG_KEYWORD_RESERVED,
+					array( 'SET', 'DROP' )
 				);
 
+				// Not all CHANGE statements have a new field definition (e.g, SET/DROP DEFAULT).
+				if ( $set_or_drop_default ) {
+					$new_field = null;
+				} else {
+					$new_field = $this->parse_mysql_create_table_field();
+				}
+
+				$alter_terminator = end( $this->rewriter->output_tokens );
+				if ( $new_field ) {
+					$this->update_data_type_cache(
+						$this->table_name,
+						$new_field->name,
+						$new_field->mysql_data_type
+					);
+				}
+
 				/*
 				 * In SQLite, there is no direct equivalent to the CHANGE COLUMN
 				 * statement from MySQL. We need to do a bit of work to emulate it.
@@ -3107,7 +3122,7 @@ private function execute_alter() {
 						WP_SQLite_Token::TYPE_KEYWORD,
 						WP_SQLite_Token::FLAG_KEYWORD_DATA_TYPE
 					);
-					if ( $is_column_definition ) {
+					if ( $new_field && $is_column_definition ) {
 						// Skip the old field definition.
 						$field_depth = $create_table->depth;
 						do {
@@ -3130,10 +3145,42 @@ private function execute_alter() {
 						// Otherwise, just add the new name in place of the old name we dropped.
 						$create_table->add(
 							new WP_SQLite_Token(
-								"`$new_field->name`",
+								'`' . ( $new_field ? $new_field->name : $from_name ) . '`',
 								WP_SQLite_Token::TYPE_KEYWORD
 							)
 						);
+
+						// Handle "CHANGE <column> DROP DEFAULT" and "CHANGE <column> SET DEFAULT <value>".
+						if ( $set_or_drop_default ) {
+							// 1. Drop "DEFAULT <value>" from old column definition.
+							$field_depth = $create_table->depth;
+							do {
+								$is_default = $create_table->peek()->matches(
+									WP_SQLite_Token::TYPE_KEYWORD,
+									WP_SQLite_Token::FLAG_KEYWORD_RESERVED,
+									array( 'DEFAULT' )
+								);
+								if ( $is_default ) {
+									$create_table->skip(); // DEFAULT
+									$create_table->skip(); // value
+								} else {
+									$create_table->consume();
+								}
+							} while (
+								! $this->is_create_table_field_terminator( $create_table->peek(), $field_depth, $create_table->depth )
+							);
+
+							// 2. For SET, add new "DEFAULT <value>" to column definition.
+							$keyword = $this->rewriter->consume();
+							if ( 'SET' === $keyword->value ) {
+								$terminator = $create_table->drop_last();
+								$create_table->add( new WP_SQLite_Token( ' ', WP_SQLite_Token::TYPE_WHITESPACE ) );
+								$create_table->add( $this->rewriter->consume() ); // DEFAULT
+								$create_table->add( new WP_SQLite_Token( ' ', WP_SQLite_Token::TYPE_WHITESPACE ) );
+								$create_table->add( $this->rewriter->consume() ); // value
+								$create_table->add( $terminator );
+							}
+						}
 					}
 				}