Add support for SHOW COLLATIONS statement

Author: JanJakes

tests/WP_SQLite_Driver_Metadata_Tests.php

@@ -467,6 +467,19 @@ public function testRepairTable() {
 		);
 	}
 
+	public function testShowCollation(): void {
+		$this->assertQuery( 'SHOW COLLATION' );
+		$actual = $this->engine->get_query_results();
+		$this->assertCount( 7, $actual );
+		$this->assertEquals( 'binary', $actual[0]->Collation );
+		$this->assertEquals( 'utf8_bin', $actual[1]->Collation );
+		$this->assertEquals( 'utf8_general_ci', $actual[2]->Collation );
+		$this->assertEquals( 'utf8_unicode_ci', $actual[3]->Collation );
+		$this->assertEquals( 'utf8mb4_bin', $actual[4]->Collation );
+		$this->assertEquals( 'utf8mb4_unicode_ci', $actual[5]->Collation );
+		$this->assertEquals( 'utf8mb4_0900_ai_ci', $actual[6]->Collation );
+	}
+
 	public function testShowDatabases(): void {
 		// Simple.
 		$this->assertQuery( 'SHOW DATABASES' );

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

@@ -2200,6 +2200,9 @@ private function execute_show_statement( WP_Parser_Node $node ): void {
 		$keyword2 = $tokens[2] ?? null;
 
 		switch ( $keyword1->id ) {
+			case WP_MySQL_Lexer::COLLATION_SYMBOL:
+				$this->execute_show_collation_statement();
+				return;
 			case WP_MySQL_Lexer::DATABASES_SYMBOL:
 				$this->execute_show_databases_statement( $node );
 				return;
@@ -2267,6 +2270,32 @@ private function execute_show_statement( WP_Parser_Node $node ): void {
 		);
 	}
 
+	/**
+	 * Translate and execute a MySQL SHOW COLLATION statement in SQLite.
+	 */
+	private function execute_show_collation_statement(): void {
+		$definition = $this->information_schema_builder
+			->get_computed_information_schema_table_definition( 'collations' );
+
+		// TODO: LIKE and WHERE clauses.
+
+		$result = $this->execute_sqlite_query( $definition )->fetchAll( PDO::FETCH_ASSOC );
+
+		$collations = array();
+		foreach ( $result as $row ) {
+			$collations[] = (object) array(
+				'Collation'     => $row['COLLATION_NAME'],
+				'Charset'       => $row['CHARACTER_SET_NAME'],
+				'Id'            => $row['ID'],
+				'Default'       => $row['IS_DEFAULT'],
+				'Compiled'      => $row['IS_COMPILED'],
+				'Sortlen'       => $row['SORTLEN'],
+				'Pad_attribute' => $row['PAD_ATTRIBUTE'],
+			);
+		}
+		$this->set_results_from_fetched_data( $collations );
+	}
+
 	/**
 	 * Translate and execute a MySQL SHOW DATABASES statement in SQLite.
 	 *