Implement syntax highlighting.

Author: myronmarston

lib/rspec/core/formatters/exception_presenter.rb

@@ -204,7 +204,8 @@ def read_failed_lines
 
           file_path, line_number = matching_line.match(/(.+?):(\d+)(|:\d+)/)[1..2]
           max_line_count = RSpec.configuration.max_displayed_failure_line_count
-          SnippetExtractor.extract_expression_lines_at(file_path, line_number.to_i, max_line_count)
+          lines = SnippetExtractor.extract_expression_lines_at(file_path, line_number.to_i, max_line_count)
+          RSpec.world.source_cache.syntax_highlighter.highlight(lines)
         rescue SnippetExtractor::NoSuchFileError
           ["Unable to find #{file_path} to read failed line"]
         rescue SnippetExtractor::NoSuchLineError

lib/rspec/core/source.rb

@@ -1,4 +1,5 @@
 RSpec::Support.require_rspec_core 'source/node'
+RSpec::Support.require_rspec_core 'source/syntax_highlighter'
 RSpec::Support.require_rspec_core 'source/token'
 
 module RSpec
@@ -58,8 +59,11 @@ def inspect
 
       # @private
       class Cache
-        def initialize
+        attr_reader :syntax_highlighter
+
+        def initialize(configuration)
           @sources_by_path = {}
+          @syntax_highlighter = SyntaxHighlighter.new(configuration)
         end
 
         def source_from_file(path)

lib/rspec/core/source/syntax_highlighter.rb

@@ -0,0 +1,57 @@
+module RSpec
+  module Core
+    class Source
+      class SyntaxHighlighter
+        def initialize(configuration)
+          @configuration = configuration
+        end
+
+        def highlight(code)
+          implementation.highlight_syntax(code)
+        end
+
+      private
+
+        def implementation
+          return color_enabled_implementation if @configuration.color_enabled?
+          ColorDisabledImplementation
+        end
+
+        def color_enabled_implementation
+          @color_enabled_implementation ||= begin
+            ::Kernel.require 'coderay'
+            CodeRayImplementation
+          rescue LoadError
+            NoCodeRayImplementation
+          end
+        end
+
+        module CodeRayImplementation
+          RESET_CODE = "\e[0m"
+
+          def self.highlight_syntax(lines)
+            highlighted = CodeRay.encode(lines.join("\n"), :ruby, :terminal)
+            highlighted.split("\n").map do |line|
+              line.sub(/\S/) { |char| char.insert(0, RESET_CODE) }
+            end
+          end
+        end
+
+        module NoCodeRayImplementation
+          INSTALL_CODERAY_COMMENT = ["# Install the coderay gem to get syntax highlighting"]
+
+          def self.highlight_syntax(lines)
+            return lines unless lines.size > 1
+            lines + INSTALL_CODERAY_COMMENT
+          end
+        end
+
+        module ColorDisabledImplementation
+          def self.highlight_syntax(lines)
+            lines
+          end
+        end
+      end
+    end
+  end
+end

lib/rspec/core/world.rb

@@ -111,7 +111,7 @@ def reporter
       def source_cache
         @source_cache ||= begin
           RSpec::Support.require_rspec_core "source"
-          Source::Cache.new
+          Source::Cache.new(@configuration)
         end
       end
 

spec/rspec/core/source/syntax_highlighter_spec.rb

@@ -0,0 +1,77 @@
+require 'rspec/core/source/syntax_highlighter'
+
+class RSpec::Core::Source
+  RSpec.describe SyntaxHighlighter do
+    let(:config)      { RSpec::Core::Configuration.new.tap { |c| c.color = true } }
+    let(:highlighter) { SyntaxHighlighter.new(config)  }
+
+    def be_highlighted
+      include("\e[32m")
+    end
+
+    context "when CodeRay is available" do
+      before { expect { require 'coderay' }.not_to raise_error }
+
+      it 'highlights the syntax of the provided lines' do
+        highlighted = highlighter.highlight(['[:ok, "ok"]'])
+        expect(highlighted.size).to eq(1)
+        expect(highlighted.first).to be_highlighted.and include(":ok")
+      end
+
+      it 'prefixes the each line with a reset escape code so it can be interpolated in a colored string without affecting the syntax highlighting of the snippet' do
+        highlighted = highlighter.highlight(['a = 1', 'b = 2'])
+        expect(highlighted).to all start_with("\e[0m")
+      end
+
+      it 'leaves leading spaces alone so it can be re-indented as needed without the leading reset code interfering' do
+        highlighted = highlighter.highlight(['  a = 1', '  b = 2'])
+        expect(highlighted).to all start_with("  \e[0m")
+      end
+
+      it 'returns the provided lines unmodified if color is disabled' do
+        config.color = false
+        expect(highlighter.highlight(['[:ok, "ok"]'])).to eq(['[:ok, "ok"]'])
+      end
+    end
+
+    context "when CodeRay is unavailable" do
+      before do
+        allow(::Kernel).to receive(:require).with("coderay").and_raise(LoadError)
+      end
+
+      it 'does not highlight the syntax' do
+        unhighlighted = highlighter.highlight(['[:ok, "ok"]'])
+        expect(unhighlighted.size).to eq(1)
+        expect(unhighlighted.first).not_to be_highlighted
+      end
+
+      it 'adds a comment explaining the user can get syntax highlighting by installing coderay' do
+        lines = ["a = 1", "b = 2"]
+        expect(highlighter.highlight(lines)).to eq([
+          "a = 1",
+          "b = 2",
+          "# Install the coderay gem to get syntax highlighting"
+        ])
+      end
+
+      it 'does not mutate the input array' do
+        lines = ["a = 1", "b = 2"]
+        expect { highlighter.highlight(lines) }.not_to change { lines }
+      end
+
+      it 'does not add the comment about coderay if the snippet is only one line as we do not want to convert it to multiline just for the comment' do
+        expect(highlighter.highlight(["a = 1"])).to eq(["a = 1"])
+      end
+
+      it 'does not add the comment about coderay if given no lines' do
+        expect(highlighter.highlight([])).to eq([])
+      end
+
+      it 'does not add the comment about coderay if color id disabled even when given a multiline snippet' do
+        config.color = false
+        lines = ["a = 1", "b = 2"]
+        expect(highlighter.highlight(lines)).to eq(lines)
+      end
+    end
+  end
+end