From 76e8d9762581f0564b7400503fdf20fb04df6352 Mon Sep 17 00:00:00 2001
From: Timo Tijhof <krinklemail@gmail.com>
Date: Wed, 24 Jan 2018 11:33:37 -0800
Subject: [PATCH] rdbms: Simplify Database::factory()

Follows-up 0ff2b7a776 (T120333) which removed support for the
deprecated php 'mysql' extension.

It surprised me that the 'DatabaseMysql' entry could safely be removed
from $classAliases. This was because the key is not direct input,
but based on $canonicalDBTypes, which maps mysql to mysqli.

Take this further by removing the indirection between type, driver
and class name.

* Map built-in db types directly to their class and driver.
* Change fallback to assign $class directly from $dbType, without
  indirection of a $driver variable.
* Remove unused $classAliases.

Change-Id: I1200b07f66f23624410d848b6f382cb2dafa5c59
---
 includes/libs/rdbms/database/Database.php | 64 +++++++++++------------
 1 file changed, 31 insertions(+), 33 deletions(-)

diff --git a/includes/libs/rdbms/database/Database.php b/includes/libs/rdbms/database/Database.php
index 323c147824..1efa9a1f2e 100644
--- a/includes/libs/rdbms/database/Database.php
+++ b/includes/libs/rdbms/database/Database.php
@@ -336,53 +336,51 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
 	 * @since 1.18
 	 */
 	final public static function factory( $dbType, $p = [] ) {
-		static $canonicalDBTypes = [
-			'mysql' => [ 'mysqli' ],
-			'postgres' => [],
-			'sqlite' => [],
-			'oracle' => [],
-			'mssql' => [],
-		];
-		static $classAliases = [
-			'DatabaseMssql' => DatabaseMssql::class,
-			'DatabaseMysqli' => DatabaseMysqli::class,
-			'DatabaseSqlite' => DatabaseSqlite::class,
-			'DatabasePostgres' => DatabasePostgres::class
+		// For database types with built-in support, the below maps type to IDatabase
+		// implementations. For types with multipe driver implementations (PHP extensions),
+		// an array can be used, keyed by extension name. In case of an array, the
+		// optional 'driver' parameter can be used to force a specific driver. Otherwise,
+		// we auto-detect the first available driver. For types without built-in support,
+		// an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
+		static $builtinTypes = [
+			'mssql' => DatabaseMssql::class,
+			'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
+			'sqlite' => DatabaseSqlite::class,
+			'postgres' => DatabasePostgres::class,
 		];
 
-		$driver = false;
 		$dbType = strtolower( $dbType );
-		if ( isset( $canonicalDBTypes[$dbType] ) && $canonicalDBTypes[$dbType] ) {
-			$possibleDrivers = $canonicalDBTypes[$dbType];
-			if ( !empty( $p['driver'] ) ) {
-				if ( in_array( $p['driver'], $possibleDrivers ) ) {
-					$driver = $p['driver'];
-				} else {
-					throw new InvalidArgumentException( __METHOD__ .
-						" type '$dbType' does not support driver '{$p['driver']}'" );
-				}
+		$class = false;
+		if ( isset( $builtinTypes[$dbType] ) ) {
+			$possibleDrivers = $builtinTypes[$dbType];
+			if ( is_string( $possibleDrivers ) ) {
+				$class = $possibleDrivers;
 			} else {
-				foreach ( $possibleDrivers as $posDriver ) {
-					if ( extension_loaded( $posDriver ) ) {
-						$driver = $posDriver;
-						break;
+				if ( !empty( $p['driver'] ) ) {
+					if ( !isset( $possibleDrivers[$p['driver']] ) ) {
+						throw new InvalidArgumentException( __METHOD__ .
+							" type '$dbType' does not support driver '{$p['driver']}'" );
+					} else {
+						$class = $possibleDrivers[$p['driver']];
+					}
+				} else {
+					foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
+						if ( extension_loaded( $posDriver ) ) {
+							$class = $possibleClass;
+							break;
+						}
 					}
 				}
 			}
 		} else {
-			$driver = $dbType;
+			$class = 'Database' . ucfirst( $dbType );
 		}
 
-		if ( $driver === false || $driver === '' ) {
+		if ( $class === false ) {
 			throw new InvalidArgumentException( __METHOD__ .
 				" no viable database extension found for type '$dbType'" );
 		}
 
-		$class = 'Database' . ucfirst( $driver );
-		if ( isset( $classAliases[$class] ) ) {
-			$class = $classAliases[$class];
-		}
-
 		if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 			// Resolve some defaults for b/c
 			$p['host'] = isset( $p['host'] ) ? $p['host'] : false;
-- 
2.20.1