Allow different indentation in the indented syntax. (#2309)

Closes #2176

doc-src/SASS_CHANGELOG.md

@@ -52,6 +52,9 @@
   [`<declaration-value>`][declaration-value] production in their argument list.
   This will provide better forwards-compatibility for future CSS syntax.
 
+* The indented syntax now allows different indentation to be used for different
+  lines, as long as they define a consistent tree structure.
+
 [hex alpha spec]: https://drafts.csswg.org/css-color/#hex-notation
 [directional focus spec]: https://www.w3.org/TR/css-ui-3/#nav-dir
 

lib/sass/engine.rb

@@ -522,10 +522,6 @@ def tree(arr, i = 0)
       nodes = []
       while (line = arr[i]) && line.tabs >= base
         if line.tabs > base
-          raise SyntaxError.new(
-            "The line was indented #{line.tabs - base} levels deeper than the previous line.",
-            :line => line.index) if line.tabs > base + 1
-
           nodes.last.children, i = tree(arr, i)
         else
           nodes << line

test/sass/engine_test.rb

@@ -98,8 +98,6 @@ class SassEngineTest < MiniTest::Test
     "a\n\t\tb: c\n\tb: c" => ["Inconsistent indentation: 1 tab was used for indentation, but the rest of the document was indented using 2 tabs.", 3],
     "a\n  b: c\n   b: c" => ["Inconsistent indentation: 3 spaces were used for indentation, but the rest of the document was indented using 2 spaces.", 3],
     "a\n  b: c\n  a\n   d: e" => ["Inconsistent indentation: 3 spaces were used for indentation, but the rest of the document was indented using 2 spaces.", 4],
-    "a\n  b: c\na\n    d: e" => ["The line was indented 2 levels deeper than the previous line.", 4],
-    "a\n  b: c\n  a\n        d: e" => ["The line was indented 3 levels deeper than the previous line.", 4],
     "a\n \tb: c" => ["Indentation can't use both tabs and spaces.", 2],
     "=a(" => 'Invalid CSS after "(": expected variable (e.g. $foo), was ""',
     "=a(b)" => 'Invalid CSS after "(": expected variable (e.g. $foo), was "b)"',