Bugfixes in SHOW CREATE TABLE and SHOW TABLES (#117)

Fixes a series of crashes encountered when

* SHOW TABLES now returns a flat list, not an array of objects – I'm not
sure here. It makes `$tables = $wpdb->get_results("SHOW TABLES LIKE
'{$prefix}%'", ARRAY_N);` work as expected
[here](https://github.com/WordPress/playground-tools/blob/128123e84e25cf0421770f6885c6f26aaf0b05dc/packages/playground/src/playground-db.php#L90-L91),
but is the right thing to return, or is this more about correct handling
of the fetch mode, like ARRAY_N?
* `SHOW tables` isn't all uppercase
* There's no table tho SHOW CREATE: `SHOW CREATE TABLE _no_such_table;`
* The table identifier passed to SHOW CREATE is quoted:

```
'SHOW CREATETABLE `_tmp_table`;'
```

This PR makes the [Sandbox site
plugin](https://wordpress.org/plugins/playground/) work in Playground

cc @bgrgicak @brandonpayton @wojtekn

tests/WP_SQLite_Translator_Tests.php

@@ -253,6 +253,14 @@ public function testSelectFromDual() {
 		$this->assertEquals( 1, $result[0]->output );
 	}
 
+	public function testShowCreateTableNotFound() {
+		$this->assertQuery(
+			'SHOW CREATE TABLE _no_such_table;'
+		);
+		$results = $this->engine->get_query_results();
+		$this->assertCount( 0, $results );
+	}
+
 	public function testShowCreateTable1() {
 		$this->assertQuery(
 			"CREATE TABLE _tmp_table (
@@ -281,6 +289,34 @@ public function testShowCreateTable1() {
 		);
 	}
 
+	public function testShowCreateTableQuoted() {
+		$this->assertQuery(
+			"CREATE TABLE _tmp_table (
+				ID BIGINT PRIMARY KEY AUTO_INCREMENT NOT NULL,
+				option_name VARCHAR(255) default '',
+				option_value TEXT NOT NULL,
+				UNIQUE KEY option_name (option_name),
+				KEY composite (option_name, option_value)
+			);"
+		);
+
+		$this->assertQuery(
+			'SHOW CREATE TABLE `_tmp_table`;'
+		);
+		$results = $this->engine->get_query_results();
+		# TODO: Should we fix mismatch with original `option_value` text NOT NULL,` without default?
+		$this->assertEquals(
+			"CREATE TABLE _tmp_table (
+	`ID` bigint PRIMARY KEY AUTO_INCREMENT NOT NULL,
+	`option_name` varchar(255) DEFAULT '',
+	`option_value` text NOT NULL DEFAULT '',
+	KEY _tmp_table__composite (option_name, option_value),
+	UNIQUE KEY _tmp_table__option_name (option_name)
+);",
+			$results[0]->{'Create Table'}
+		);
+	}
+
 	public function testShowCreateTableSimpleTable() {
 		$this->assertQuery(
 			'CREATE TABLE _tmp_table (
@@ -417,9 +453,7 @@ public function testShowTablesLike() {
 		);
 		$this->assertEquals(
 			array(
-				(object) array(
-					'Tables_in_db' => '_tmp_table',
-				),
+				'_tmp_table',
 			),
 			$this->engine->get_query_results()
 		);

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

@@ -3238,8 +3238,8 @@ private function execute_drop() {
 	 */
 	private function execute_show() {
 		$this->rewriter->skip();
-		$what1 = $this->rewriter->consume()->token;
-		$what2 = $this->rewriter->consume()->token;
+		$what1 = strtoupper( $this->rewriter->consume()->token );
+		$what2 = strtoupper( $this->rewriter->consume()->token );
 		$what  = $what1 . ' ' . $what2;
 		switch ( $what ) {
 			case 'CREATE PROCEDURE':
@@ -3338,10 +3338,18 @@ private function execute_show() {
 				return;
 
 			case 'CREATE TABLE':
-				$table_name = $this->rewriter->consume()->token;
+				// Value is unquoted table name
+				$table_name = $this->rewriter->consume()->value;
 				$columns    = $this->get_columns_from( $table_name );
 				$keys       = $this->get_keys( $table_name );
 
+				if ( empty( $columns ) ) {
+					$this->set_results_from_fetched_data(
+						array()
+					);
+					return;
+				}
+
 				foreach ( $columns as $column ) {
 					$column      = (array) $column;
 					$definition  = '';
@@ -3452,8 +3460,12 @@ private function execute_show() {
 						':param' => $table_expression->value,
 					)
 				);
+
 				$this->set_results_from_fetched_data(
-					$stmt->fetchAll( $this->pdo_fetch_mode )
+					array_column(
+						$stmt->fetchAll( $this->pdo_fetch_mode ),
+						'Tables_in_db'
+					)
 				);
 				return;
 
@@ -3464,7 +3476,10 @@ private function execute_show() {
 							"SELECT name FROM sqlite_master WHERE type='table'"
 						);
 						$this->set_results_from_fetched_data(
-							$stmt->fetchAll( $this->pdo_fetch_mode )
+							array_column(
+								$stmt->fetchAll( $this->pdo_fetch_mode ),
+								'Tables_in_db'
+							)
 						);
 						return;