Html::openElement() micro-optimisations

* Use isset() instead of in_array()

In dropDefaults():
* Remove strtolower(), since the performance cost of running
  strtolower() on all attribute names far outweighs the performance
  benefit of dropping default values for attributes with non-canonical
  capitalisation. Attribute names with non-canonical case are extremely
  rare in the MediaWiki ecosystem. The change is harmless in the sense
  that a default attribute is semantically equivalent to an omitted
  attribute.
* Handle common cases first.
* Avoid value normalization when the attribute name is unknown.
* For class attributes, check if the value is empty using strict
  comparison rather than normalization.

In expandAttributes():
* If the value is an array, explode each element and add the parts to
  an array rather than doing implode() then explode().
* If the value is an array, check for spaces in the loop rather than
  calling array_diff().
* Replace $quote with a literal
* Skip the check for boolean attributes if we already know it is a
  space-separated attribute.
* Inline Sanitizer::encodeAttribute

Measuring instruction count per iteration with perf stat, averaged over
10M iterations, PS1. Test case:
Html::openElement('a', [ 'class' => [ 'foo', 'bar' ] ] )

* Baseline: 11160.7265433
* in_array(): 10390.3837233
* dropDefaults() changes: 9674.1248824
* expandAttributes() misc: 9248.1947500
* implode/explode and space check: 8318.9800417
* Sanitizer inline: 8021.7371794

Change-Id: I7680b8939da50430316d77d42ebc1987752e99dc

1 files changed, 135 insertions, 109 deletions

diff --git a/includes/Html.php b/includes/Html.php
index 3ffea80dcff8..8b19456debfc 100644
--- a/includes/Html.php
+++ b/includes/Html.php
@@ -47,59 +47,57 @@ use MediaWiki\MediaWikiServices;
  * @since 1.16
  */
 class Html {
-	/** @var string[] List of void elements from HTML5, section 8.1.2 as of 2016-09-19 */
+	/** @var bool[] List of void elements from HTML5, section 8.1.2 as of 2016-09-19 */
 	private static $voidElements = [
-		'area',
-		'base',
-		'br',
-		'col',
-		'embed',
-		'hr',
-		'img',
-		'input',
-		'keygen',
-		'link',
-		'meta',
-		'param',
-		'source',
-		'track',
-		'wbr',
+		'area' => true,
+		'base' => true,
+		'br' => true,
+		'col' => true,
+		'embed' => true,
+		'hr' => true,
+		'img' => true,
+		'input' => true,
+		'keygen' => true,
+		'link' => true,
+		'meta' => true,
+		'param' => true,
+		'source' => true,
+		'track' => true,
+		'wbr' => true,
 	];
 
 	/**
 	 * Boolean attributes, which may have the value omitted entirely.  Manually
 	 * collected from the HTML5 spec as of 2011-08-12.
-	 * @var string[]
+	 * @var bool[]
 	 */
 	private static $boolAttribs = [
-		'async',
-		'autofocus',
-		'autoplay',
-		'checked',
-		'controls',
-		'default',
-		'defer',
-		'disabled',
-		'formnovalidate',
-		'hidden',
-		'ismap',
-		'itemscope',
-		'loop',
-		'multiple',
-		'muted',
-		'novalidate',
-		'open',
-		'pubdate',
-		'readonly',
-		'required',
-		'reversed',
-		'scoped',
-		'seamless',
-		'selected',
-		'truespeed',
-		'typemustmatch',
-		// HTML5 Microdata
-		'itemscope',
+		'async' => true,
+		'autofocus' => true,
+		'autoplay' => true,
+		'checked' => true,
+		'controls' => true,
+		'default' => true,
+		'defer' => true,
+		'disabled' => true,
+		'formnovalidate' => true,
+		'hidden' => true,
+		'ismap' => true,
+		'itemscope' => true,
+		'loop' => true,
+		'multiple' => true,
+		'muted' => true,
+		'novalidate' => true,
+		'open' => true,
+		'pubdate' => true,
+		'readonly' => true,
+		'required' => true,
+		'reversed' => true,
+		'scoped' => true,
+		'seamless' => true,
+		'selected' => true,
+		'truespeed' => true,
+		'typemustmatch' => true,
 	];
 
 	/**
@@ -211,7 +209,7 @@ class Html {
 	 */
 	public static function rawElement( $element, $attribs = [], $contents = '' ) {
 		$start = self::openElement( $element, $attribs );
-		if ( in_array( $element, self::$voidElements ) ) {
+		if ( isset( self::$voidElements[$element] ) ) {
 			// Silly XML.
 			return substr( $start, 0, -1 ) . '/>';
 		} else {
@@ -266,33 +264,33 @@ class Html {
 		// Remove invalid input types
 		if ( $element == 'input' ) {
 			$validTypes = [
-				'hidden',
-				'text',
-				'password',
-				'checkbox',
-				'radio',
-				'file',
-				'submit',
-				'image',
-				'reset',
-				'button',
+				'hidden' => true,
+				'text' => true,
+				'password' => true,
+				'checkbox' => true,
+				'radio' => true,
+				'file' => true,
+				'submit' => true,
+				'image' => true,
+				'reset' => true,
+				'button' => true,
 
 				// HTML input types
-				'datetime',
-				'datetime-local',
-				'date',
-				'month',
-				'time',
-				'week',
-				'number',
-				'range',
-				'email',
-				'url',
-				'search',
-				'tel',
-				'color',
+				'datetime' => true,
+				'datetime-local' => true,
+				'date' => true,
+				'month' => true,
+				'time' => true,
+				'week' => true,
+				'number' => true,
+				'range' => true,
+				'email' => true,
+				'url' => true,
+				'search' => true,
+				'tel' => true,
+				'color' => true,
 			];
-			if ( isset( $attribs['type'] ) && !in_array( $attribs['type'], $validTypes ) ) {
+			if ( isset( $attribs['type'] ) && !isset( $validTypes[$attribs['type']] ) ) {
 				unset( $attribs['type'] );
 			}
 		}
@@ -371,25 +369,20 @@ class Html {
 			'textarea' => [ 'wrap' => 'soft' ],
 		];
 
-		$element = strtolower( $element );
-
 		foreach ( $attribs as $attrib => $value ) {
-			$lcattrib = strtolower( $attrib );
-			if ( is_array( $value ) ) {
-				$value = implode( ' ', $value );
-			} else {
-				$value = strval( $value );
-			}
-
-			// Simple checks using $attribDefaults
-			if ( isset( $attribDefaults[$element][$lcattrib] )
-				&& $attribDefaults[$element][$lcattrib] == $value
-			) {
-				unset( $attribs[$attrib] );
-			}
-
-			if ( $lcattrib == 'class' && $value == '' ) {
-				unset( $attribs[$attrib] );
+			if ( $attrib === 'class' ) {
+				if ( $value === '' || $value === [] || $value === [ '' ] ) {
+					unset( $attribs[$attrib] );
+				}
+			} elseif ( isset( $attribDefaults[$element][$attrib] ) ) {
+				if ( is_array( $value ) ) {
+					$value = implode( ' ', $value );
+				} else {
+					$value = strval( $value );
+				}
+				if ( $attribDefaults[$element][$attrib] == $value ) {
+					unset( $attribs[$attrib] );
+				}
 			}
 		}
 
@@ -490,7 +483,7 @@ class Html {
 
 			// For boolean attributes, support [ 'foo' ] instead of
 			// requiring [ 'foo' => 'meaningless' ].
-			if ( is_int( $key ) && in_array( strtolower( $value ), self::$boolAttribs ) ) {
+			if ( is_int( $key ) && isset( self::$boolAttribs[strtolower( $value )] ) ) {
 				$key = $value;
 			}
 
@@ -501,23 +494,23 @@ class Html {
 			// https://www.w3.org/TR/html401/index/attributes.html ("space-separated")
 			// https://www.w3.org/TR/html5/index.html#attributes-1 ("space-separated")
 			$spaceSeparatedListAttributes = [
-				'class', // html4, html5
-				'accesskey', // as of html5, multiple space-separated values allowed
+				'class' => true, // html4, html5
+				'accesskey' => true, // as of html5, multiple space-separated values allowed
 				// html4-spec doesn't document rel= as space-separated
 				// but has been used like that and is now documented as such
 				// in the html5-spec.
-				'rel',
+				'rel' => true,
 			];
 
 			// Specific features for attributes that allow a list of space-separated values
-			if ( in_array( $key, $spaceSeparatedListAttributes ) ) {
+			if ( isset( $spaceSeparatedListAttributes[$key] ) ) {
 				// Apply some normalization and remove duplicates
 
 				// Convert into correct array. Array can contain space-separated
 				// values. Implode/explode to get those into the main array as well.
 				if ( is_array( $value ) ) {
 					// If input wasn't an array, we can skip this step
-					$newValue = [];
+					$arrayValue = [];
 					foreach ( $value as $k => $v ) {
 						if ( is_string( $v ) ) {
 							// String values should be normal `[ 'foo' ]`
@@ -526,34 +519,55 @@ class Html {
 								// As a special case don't set 'foo' if a
 								// separate 'foo' => true/false exists in the array
 								// keys should be authoritative
-								$newValue[] = $v;
+								foreach ( explode( ' ', $v ) as $part ) {
+									// Normalize spacing by fixing up cases where people used
+									// more than 1 space and/or a trailing/leading space
+									if ( $part !== '' && $part !== ' ' ) {
+										$arrayValue[] = $part;
+									}
+								}
 							}
 						} elseif ( $v ) {
 							// If the value is truthy but not a string this is likely
 							// an [ 'foo' => true ], falsy values don't add strings
-							$newValue[] = $k;
+							$arrayValue[] = $k;
 						}
 					}
-					$value = implode( ' ', $newValue );
+				} else {
+					$arrayValue = explode( ' ', $value );
+					// Normalize spacing by fixing up cases where people used
+					// more than 1 space and/or a trailing/leading space
+					$arrayValue = array_diff( $arrayValue, [ '', ' ' ] );
 				}
-				$value = explode( ' ', $value );
-
-				// Normalize spacing by fixing up cases where people used
-				// more than 1 space and/or a trailing/leading space
-				$value = array_diff( $value, [ '', ' ' ] );
 
 				// Remove duplicates and create the string
-				$value = implode( ' ', array_unique( $value ) );
+				$value = implode( ' ', array_unique( $arrayValue ) );
+
+				// Optimization: Skip below boolAttribs check and jump straight
+				// to its `else` block. The current $spaceSeparatedListAttributes
+				// block is mutually exclusive with $boolAttribs.
+				// phpcs:ignore Generic.PHP.DiscourageGoto
+				goto not_bool; // NOSONAR
 			} elseif ( is_array( $value ) ) {
 				throw new MWException( "HTML attribute $key can not contain a list of values" );
 			}
 
-			$quote = '"';
-
-			if ( in_array( $key, self::$boolAttribs ) ) {
+			if ( isset( self::$boolAttribs[$key] ) ) {
 				$ret .= " $key=\"\"";
 			} else {
-				$ret .= " $key=$quote" . Sanitizer::encodeAttribute( $value ) . $quote;
+				// phpcs:ignore Generic.PHP.DiscourageGoto
+				not_bool:
+				// Inlined from Sanitizer::encodeAttribute() for improved performance
+				$encValue = htmlspecialchars( $value, ENT_QUOTES );
+				// Whitespace is normalized during attribute decoding,
+				// so if we've been passed non-spaces we must encode them
+				// ahead of time or they won't be preserved.
+				$encValue = strtr( $encValue, [
+					"\n" => '
',
+					"\r" => '
',
+					"\t" => '	',
+				] );
+				$ret .= " $key=\"$encValue\"";
 			}
 		}
 		return $ret;
@@ -671,10 +685,22 @@ class Html {
 		$attribs['type'] = $type;
 		$attribs['value'] = $value;
 		$attribs['name'] = $name;
-		if ( in_array( $type, [ 'text', 'search', 'email', 'password', 'number' ] ) ) {
+		$textInputAttributes = [
+			'text' => true,
+			'search' => true,
+			'email' => true,
+			'password' => true,
+			'number' => true
+		];
+		if ( isset( $textInputAttributes[$type] ) ) {
 			$attribs = self::getTextInputAttributes( $attribs );
 		}
-		if ( in_array( $type, [ 'button', 'reset', 'submit' ] ) ) {
+		$buttonAttributes = [
+			'button' => true,
+			'reset' => true,
+			'submit' => true
+		];
+		if ( isset( $buttonAttributes[$type] ) ) {
 			$attribs = self::buttonAttributes( $attribs );
 		}
 		return self::element( 'input', $attribs );