[ruby/prism] Rename line_to_byte_offset -> byte_offset

Also, include the column in here. Hopefully we can do some additional
optimizations later.

https://github.com/ruby/prism/commit/7759acdd26

4 files changed, 46 insertions, 41 deletions

diff --git a/lib/prism/lex_compat.rb b/lib/prism/lex_compat.rb
index 523ad39586..4960230bcf 100644
--- a/lib/prism/lex_compat.rb
+++ b/lib/prism/lex_compat.rb
@@ -816,7 +816,7 @@ module Prism
       # Manually implemented instead of `sort_by!(&:location)` for performance.
       tokens.sort_by! do |token|
         line, column = token.location
-        source.line_to_byte_offset(line) + column
+        source.byte_offset(line, column)
       end
 
       # Add :on_sp tokens
@@ -833,8 +833,10 @@ module Prism
 
       tokens.each do |token|
         line, column = token.location
-        start_offset = source.line_to_byte_offset(line) + column
-        # Ripper reports columns on line 1 without counting the BOM, so we adjust to get the real offset
+        start_offset = source.byte_offset(line, column)
+
+        # Ripper reports columns on line 1 without counting the BOM, so we
+        # adjust to get the real offset
         start_offset += 3 if line == 1 && bom
 
         if start_offset > prev_token_end
diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 12d19da562..be1c13f97c 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -76,13 +76,13 @@ module Prism
       source.byteslice(byte_offset, length) or raise
     end
 
-    # Converts the line number to a byte offset corresponding to the start of that line
-    def line_to_byte_offset(line)
-      l = line - @start_line
-      if l < 0 || l >= offsets.size
-        raise ArgumentError, "line #{line} is out of range"
-      end
-      offsets[l]
+    # Converts the line number and column in bytes to a byte offset.
+    def byte_offset(line, column)
+      normal = line - @start_line
+      raise IndexError if normal < 0
+      offsets.fetch(normal) + column
+    rescue IndexError
+      raise ArgumentError, "line #{line} is out of range"
     end
 
     # Binary search through the offsets to find the line number for the given
diff --git a/prism/templates/lib/prism/node.rb.erb b/prism/templates/lib/prism/node.rb.erb
index 8225bfb328..6f8e8b0acc 100644
--- a/prism/templates/lib/prism/node.rb.erb
+++ b/prism/templates/lib/prism/node.rb.erb
@@ -183,14 +183,13 @@ module Prism
     def tunnel(line, column)
       queue = [self] #: Array[Prism::node]
       result = [] #: Array[Prism::node]
-
-      search_offset = source.line_to_byte_offset(line) + column
+      offset = source.byte_offset(line, column)
 
       while (node = queue.shift)
         result << node
 
         node.each_child_node do |child_node|
-          if child_node.start_offset <= search_offset && search_offset < child_node.end_offset
+          if child_node.start_offset <= offset && offset < child_node.end_offset
             queue << child_node
             break
           end
diff --git a/test/prism/ruby/source_test.rb b/test/prism/ruby/source_test.rb
index afd2825765..f7cf4fe83a 100644
--- a/test/prism/ruby/source_test.rb
+++ b/test/prism/ruby/source_test.rb
@@ -4,44 +4,48 @@ require_relative "../test_helper"
 
 module Prism
   class SourceTest < TestCase
-    def test_line_to_byte_offset
-      parse_result = Prism.parse(<<~SRC)
+    def test_byte_offset
+      source = Prism.parse(<<~SRC).source
       abcd
       efgh
       ijkl
       SRC
-      source = parse_result.source
-
-      assert_equal 0, source.line_to_byte_offset(1)
-      assert_equal 5, source.line_to_byte_offset(2)
-      assert_equal 10, source.line_to_byte_offset(3)
-      assert_equal 15, source.line_to_byte_offset(4)
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(5) }
-      assert_equal "line 5 is out of range", e.message
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(0) }
-      assert_equal "line 0 is out of range", e.message
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(-1) }
-      assert_equal "line -1 is out of range", e.message
+
+      assert_equal 0, source.byte_offset(1, 0)
+      assert_equal 5, source.byte_offset(2, 0)
+      assert_equal 10, source.byte_offset(3, 0)
+      assert_equal 15, source.byte_offset(4, 0)
+
+      error = assert_raise(ArgumentError) { source.byte_offset(5, 0) }
+      assert_equal "line 5 is out of range", error.message
+
+      error = assert_raise(ArgumentError) { source.byte_offset(0, 0) }
+      assert_equal "line 0 is out of range", error.message
+
+      error = assert_raise(ArgumentError) { source.byte_offset(-1, 0) }
+      assert_equal "line -1 is out of range", error.message
     end
 
-    def test_line_to_byte_offset_with_start_line
-      parse_result = Prism.parse(<<~SRC, line: 11)
+    def test_byte_offset_with_start_line
+      source = Prism.parse(<<~SRC, line: 11).source
       abcd
       efgh
       ijkl
       SRC
-      source = parse_result.source
-
-      assert_equal 0, source.line_to_byte_offset(11)
-      assert_equal 5, source.line_to_byte_offset(12)
-      assert_equal 10, source.line_to_byte_offset(13)
-      assert_equal 15, source.line_to_byte_offset(14)
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(15) }
-      assert_equal "line 15 is out of range", e.message
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(10) }
-      assert_equal "line 10 is out of range", e.message
-      e = assert_raise(ArgumentError) { source.line_to_byte_offset(9) }
-      assert_equal "line 9 is out of range", e.message
+
+      assert_equal 0, source.byte_offset(11, 0)
+      assert_equal 5, source.byte_offset(12, 0)
+      assert_equal 10, source.byte_offset(13, 0)
+      assert_equal 15, source.byte_offset(14, 0)
+
+      error = assert_raise(ArgumentError) { source.byte_offset(15, 0) }
+      assert_equal "line 15 is out of range", error.message
+
+      error = assert_raise(ArgumentError) { source.byte_offset(10, 0) }
+      assert_equal "line 10 is out of range", error.message
+
+      error = assert_raise(ArgumentError) { source.byte_offset(9, 0) }
+      assert_equal "line 9 is out of range", error.message
     end
   end
 end