[ruby/prism] Add Location#chop

5dd57f4b84

lib/prism/desugar_compiler.rb

@@ -73,6 +73,8 @@ module Prism
 
     # Desugar `x += y` to `x = x + y`
     def compile
+      operator_loc = node.operator_loc.chop
+
       write_class.new(
         source,
         *arguments,
@@ -82,8 +84,8 @@ module Prism
           0,
           read_class.new(source, *arguments, node.name_loc),
           nil,
-          node.operator_loc.slice.chomp("=").to_sym,
+          operator_loc.slice.to_sym,
-          node.operator_loc.copy(length: node.operator_loc.length - 1),
+          operator_loc,
           nil,
           ArgumentsNode.new(source, 0, [node.value], node.value.location),
           nil,

lib/prism/parse_result.rb

@@ -161,6 +161,11 @@ module Prism
       Location.new(source, start_offset, length)
     end
 
+    # Returns a new location that is the result of chopping off the last byte.
+    def chop
+      copy(length: length == 0 ? length : length - 1)
+    end
+
     # Returns a string representation of this location.
     def inspect
       "#<Prism::Location @start_offset=#{@start_offset} @length=#{@length} start_line=#{start_line}>"

test/prism/ruby_api_test.rb

@@ -198,6 +198,17 @@ module Prism
       assert_equal 7, location.end_code_units_column(Encoding::UTF_32LE)
     end
 
+    def test_location_chop
+      location = Prism.parse("foo").value.location
+
+      assert_equal "fo", location.chop.slice
+      assert_equal "", location.chop.chop.chop.slice
+
+      # Check that we don't go negative.
+      10.times { location = location.chop }
+      assert_equal "", location.slice
+    end
+
     def test_heredoc?
       refute parse_expression("\"foo\"").heredoc?
       refute parse_expression("\"foo \#{1}\"").heredoc?