Fix buffer for empty string

Author: soutaro

lib/rbs/buffer.rb

@@ -29,19 +29,24 @@ def line_count
 
     def ranges
       @ranges ||= begin
-        lines = content.lines
-        lines << "" if content.end_with?("\n")
-
-        ranges = [] #: Array[Range[Integer]]
-        offset = 0
-
-        lines.each do |line|
-          size0 = line.size
-          line = line.chomp
-          range = offset...(offset+line.size)
-          ranges << range
-
-          offset += size0
+        if content.empty? 
+          ranges = [0...0] #: Array[Range[Integer]]
+          lines = [""]
+        else
+          lines = content.lines
+          lines << "" if content.end_with?("\n")
+
+          ranges = [] #: Array[Range[Integer]]
+          offset = 0
+
+          lines.each do |line|
+            size0 = line.size
+            line = line.chomp
+            range = offset...(offset+line.size)
+            ranges << range
+
+            offset += size0
+          end
         end
 
         ranges

test/rbs/ast/ruby/comment_block_test.rb

@@ -144,6 +144,21 @@ def test_each_paragraph
     end
   end
 
+  def test_each_paragraph__empty
+    buffer, comments = parse_comments(<<~RUBY)
+      #
+    RUBY
+
+    block = CommentBlock.new(buffer, comments)
+
+    paragraphs = block.each_paragraph([]).to_a
+
+    paragraphs[0].tap do |paragraph|
+      assert_instance_of RBS::Location, paragraph
+      assert_equal "", paragraph.local_source
+    end
+  end
+
   def test_each_paragraph_colon
     buffer, comments = parse_comments(<<~RUBY)
       # : Foo

test/rbs/buffer_test.rb

@@ -96,4 +96,23 @@ def test_sub_buffer
       assert_equal [3, 0], sub_buffer.pos_to_loc(6)
     end
   end
+
+  def test_empty_buffer
+    buffer = Buffer.new(name: Pathname("foo.rbs"), content: "")
+
+    assert_equal "", buffer.content
+    assert_equal [""], buffer.lines
+    assert_equal [0...0], buffer.ranges
+    assert_equal "", buffer.content
+  end
+
+  def test_empty_sub_buffer
+    buffer = Buffer.new(name: Pathname("foo.rbs"), content: "")
+
+    sub_buffer = buffer.sub_buffer(lines: [0...0])
+    assert_equal "", sub_buffer.content
+    assert_equal [""], sub_buffer.lines
+    assert_equal [0...0], sub_buffer.ranges
+    assert_equal "", sub_buffer.content
+  end
 end