Support "CONSTRAINT name" clause

Author: JanJakes

tests/WP_SQLite_Driver_Tests.php

@@ -4704,6 +4704,41 @@ public function testAlterTableDuplicateKeyNameWithUnique(): void {
 		$this->assertSame( '42S21', $exception->getCode() );
 	}
 
+	public function testConstraintName(): void {
+		$this->assertQuery(
+			'CREATE TABLE t ( id INT, CONSTRAINT cst_id UNIQUE (id) )'
+		);
+
+		$result = $this->assertQuery( 'SHOW INDEX FROM t' );
+		$this->assertCount( 1, $result );
+		$this->assertSame( 'cst_id', $result[0]->Key_name );
+	}
+
+	public function testIndexNamePrecedesConstraintName(): void {
+		$this->assertQuery(
+			'CREATE TABLE t ( id INT, CONSTRAINT cst_id UNIQUE idx_id (id) )'
+		);
+
+		$result = $this->assertQuery( 'SHOW INDEX FROM t' );
+		$this->assertCount( 1, $result );
+		$this->assertSame( 'idx_id', $result[0]->Key_name );
+
+		$result = $this->assertQuery( 'SHOW CREATE TABLE t' );
+		$this->assertCount( 1, $result );
+		$this->assertSame(
+			implode(
+				"\n",
+				array(
+					'CREATE TABLE `t` (',
+					'  `id` int DEFAULT NULL,',
+					'  UNIQUE KEY `idx_id` (`id`)',
+					') ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci',
+				)
+			),
+			$result[0]->{'Create Table'}
+		);
+	}
+
 	public function testNoBackslashEscapesSqlMode(): void {
 		$backslash = chr( 92 );
 

wp-includes/sqlite-ast/class-wp-sqlite-information-schema-builder.php

@@ -1657,7 +1657,19 @@ private function get_index_name( WP_Parser_Node $node ): string {
 			return 'PRIMARY';
 		}
 
+		/*
+		 * Get index name.
+		 *
+		 * When both index and constraint name are defined, the index name will
+		 * be used. E.g., in "CONSTRAINT c UNIQUE u (id)", the name will be "u".
+		 */
 		$name_node = $node->get_first_descendant_node( 'indexName' );
+		if ( null === $name_node && $node->has_child_node( 'constraintName' ) ) {
+			$name_node = $node
+				->get_first_child_node( 'constraintName' )
+				->get_first_child_node( 'identifier' );
+		}
+
 		if ( null === $name_node ) {
 			/*
 			 * In MySQL, the default index name equals the first column name.