Support for conditional comments in RuboCop linter (#469)

lib/haml_lint/ruby_extraction/chunk_extractor.rb

@@ -84,7 +84,35 @@ def visit_haml_comment(node)
     def visit_comment(node)
       line = @original_haml_lines[node.line - 1]
       indent = line.index(/\S/)
+
       @ruby_chunks << PlaceholderMarkerChunk.new(node, 'comment', indent: indent)
+
+      # Comment can have subnodes, such as plain. This happens for conditional comments, such as:
+      # %head
+      #   /[if mso]
+      #     %div
+      if node.children
+        # We don't want to use a block because assignments in a block are local to that block,
+        # so the semantics of the extracted ruby would be different from the one generated by
+        # Haml. Those differences can make some cops, such as UselessAssignment, have false
+        # positives
+        begin_chunk = AdHocChunk.new(node, [' ' * indent + 'begin'])
+        @ruby_chunks << begin_chunk
+        indent += 2
+
+        yield
+
+        indent -= 2
+
+        if @ruby_chunks.last.equal?(begin_chunk)
+          # So there is nothing nesting, remove the wrapping "begin"
+          @ruby_chunks.pop
+        else
+          @ruby_chunks << AdHocChunk.new(node,
+                                         [' ' * indent + 'ensure', ' ' * indent + '  HL.noop', ' ' * indent + 'end'],
+                                         haml_line_index: @ruby_chunks.last.haml_end_line_index)
+        end
+      end
     end
 
     # Visit a script which outputs. Lines looking like `  = foo`

spec/haml_lint/linter/rubocop_autocorrect_examples/conditional_comments.txt

@@ -0,0 +1,39 @@
+!!! Removes indentation of a conditional comment's content
+- if a
+  - if b
+    /[if mso]
+      %div
+---
+SKIP
+---
+SKIP
+---
+- if a && b
+  /[if mso]
+    %div
+
+
+!!! fixes a single-line script that is inside a conditional comment
+/[if mso]
+  ^ foo(:bar =>  123)
+---
+haml_lint_comment_1
+begin
+  haml_lint_marker_3 $$2
+  ^^foo(:bar =>  123)
+  haml_lint_marker_5
+ensure
+  HL.noop
+end
+---
+haml_lint_comment_1
+begin
+  haml_lint_marker_3
+  ^^foo(bar: 123)
+  haml_lint_marker_5
+ensure
+  HL.noop
+end
+---
+/[if mso]
+  ^ foo(bar: 123)