Add support for @elseif (#317)

Closes #316

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 1.3.2
+
+* Add support for `@elseif` as an alias of `@else if`. This is not an
+  intentional feature, so using it will cause a deprecation warning. It will be
+  removed at some point in the future.
+
 ## 1.3.1
 
 ### Node API

lib/src/parse/parser.dart

@@ -21,11 +21,12 @@ abstract class Parser {
   final SpanScanner scanner;
 
   /// The logger to use when emitting warnings.
-  final Logger _logger;
+  @protected
+  final Logger logger;
 
   Parser(String contents, {url, Logger logger})
       : scanner = new SpanScanner(contents, sourceUrl: url),
-        _logger = logger ?? const Logger.stderr();
+        logger = logger ?? const Logger.stderr();
 
   // ## Tokens
 
@@ -566,7 +567,7 @@ abstract class Parser {
 
   /// Prints a warning to standard error, associated with [span].
   @protected
-  void warn(String message, FileSpan span) => _logger.warn(message, span: span);
+  void warn(String message, FileSpan span) => logger.warn(message, span: span);
 
   /// Prints a source span highlight of the current location being scanned.
   ///

lib/src/parse/scss.dart

@@ -41,7 +41,20 @@ class ScssParser extends StylesheetParser {
   bool scanElse(int _) {
     var start = scanner.state;
     whitespace();
-    if (scanner.scanChar($at) && scanIdentifier('else')) return true;
+    var beforeAt = scanner.state;
+    if (scanner.scanChar($at)) {
+      if (scanIdentifier('else')) return true;
+      if (scanIdentifier('elseif')) {
+        logger.warn(
+            '@elseif is deprecated and will not be supported in future Sass '
+            'versions.\n'
+            'Use "@else if" instead.',
+            span: scanner.spanFrom(beforeAt),
+            deprecation: true);
+        scanner.position -= 2;
+        return true;
+      }
+    }
     scanner.state = start;
     return false;
   }

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.3.1
+version: 1.3.2
 description: A Sass implementation in Dart.
 author: Dart Team <[email protected]>
 homepage: https://github.com/sass/dart-sass