Refactor error context line option handling

Use same terminology in options and code. Drop support for environment variable as that is not available for any other option.

lib/uglifier.rb

@@ -230,14 +230,11 @@ def harmony_error_message(message)
     end
   end
 
-  def populate_surround_size
-    surround_size = ENV['ERROR_CONTEXT_LINES'].to_i
-    surround_size = @options[:error_context_lines].to_i if surround_size <= 0
-    surround_size = DEFAULTS[:error_context_lines] if surround_size <= 0
-    surround_size
+  def error_context_lines
+    @options.fetch(:error_context_lines, DEFAULTS[:error_context_lines]).to_i
   end
 
-  def populate_format_options(low, high, line_index, col)
+  def error_context_format_options(low, high, line_index, col)
     line_width = high.to_s.size
     {
       :line_index => line_index,
@@ -268,11 +265,10 @@ def format_lines(lines, options)
   def context_lines_message(source, line_no, col)
     line_index = line_no - 1
     lines = source.split("\n")
-    surround_size = populate_surround_size
 
-    base_index = [line_index - surround_size, 0].max
-    high_no = [line_no + surround_size, lines.size].min
-    options = populate_format_options(base_index, high_no, line_index, col)
+    base_index = [line_index - error_context_lines, 0].max
+    high_no = [line_no + error_context_lines, lines.size].min
+    options = error_context_format_options(base_index, high_no, line_index, col)
     context_lines = lines[base_index...high_no]
 
     "--\n#{format_lines(context_lines, options).join("\n")}\n=="

spec/uglifier_spec.rb

@@ -749,7 +749,6 @@
     end
 
     it 'contains harmony error message and follows error_context_lines option' do
-      ENV['ERROR_CONTEXT_LINES'] = nil
       expect { Uglifier.compile(code, :harmony => false, :error_context_lines => 4) }
         .to raise_error(Uglifier::Error, %r{
           harmony\smode [^\n]+ Uglifier\.new  # harmony error mesage
@@ -759,20 +758,8 @@
         }xm)
     end
 
-    it 'follows ENV.ERROR_CONTEXT_LINES instead of error_context_lines option' do
-      ENV['ERROR_CONTEXT_LINES'] = '2'
-      expect { Uglifier.compile(code, :harmony => false, :error_context_lines => 4) }
-        .to raise_error(Uglifier::Error, %r{
-          harmony\smode [^\n]+ Uglifier\.new  # harmony error mesage
-          .+ --\n [^\n]+ //_1\n               # 1 should be the first line
-          .+ => [^\n]+ bar \e\[\d+m \(\)      # should point to () at line 3
-          .+ //_5\n ==\z                      # 5 should be the last line
-        }xm)
-    end
-
     it 'shows lines surrounded syntax error when harmony mode is on' do
-      ENV['ERROR_CONTEXT_LINES'] = '2'
-      expect { Uglifier.compile(code, :harmony => true) }
+      expect { Uglifier.compile(code, :harmony => true, :error_context_lines => 2) }
         .to raise_error(Uglifier::Error, %r{
           Unexpect[^\n]+ ; [^\n]+expect [^\n]+ ,  # syntax error mesage
           .+ --\n [^\n]+ //_16\n                  # 16 should be the first line