From 607f6619c1fc3a0773805a5b030ce19fd077857c Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashi-kokubun@cookpad.com>
Date: Fri, 15 Jan 2016 18:46:37 +0900
Subject: [PATCH 1/2] Show sass file on the top of backtrace

---
 lib/sassc/error.rb | 21 ++++++++++++++++++++-
 test/error_test.rb | 22 ++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 test/error_test.rb

diff --git a/lib/sassc/error.rb b/lib/sassc/error.rb
index c508c8d9..0c90b1c0 100644
--- a/lib/sassc/error.rb
+++ b/lib/sassc/error.rb
@@ -1,9 +1,28 @@
+require 'pathname'
 require 'sass/error'
 
 module SassC
   class BaseError < StandardError; end
-  class SyntaxError < BaseError; end
   class NotRenderedError < BaseError; end
   class InvalidStyleError < BaseError; end
   class UnsupportedValue < BaseError; end
+
+  # When dealing with SyntaxErrors,
+  # it's important to provide filename and line number information.
+  # This will be used in various error reports to users, including backtraces;
+  class SyntaxError < BaseError
+    def backtrace
+      return nil if super.nil?
+      sass_backtrace + super
+    end
+
+    # The backtrace of the error within Sass files.
+    def sass_backtrace
+      line_info = message.split("\n")[1]
+      return [] unless line_info
+
+      _, line, filename = line_info.match(/on line (\d+) of (.+)/).to_a
+      ["#{Pathname.getwd.join(filename)}:#{line}"]
+    end
+  end
 end
diff --git a/test/error_test.rb b/test/error_test.rb
new file mode 100644
index 00000000..20fd0b0a
--- /dev/null
+++ b/test/error_test.rb
@@ -0,0 +1,22 @@
+require_relative "test_helper"
+
+module SassC
+  class ErrorTest < MiniTest::Test
+    def test_first_backtrace_is_sass
+      line     = 2
+      filename = "app/assets/stylesheets/application.scss"
+
+      begin
+        raise SassC::SyntaxError.new(<<-ERROR)
+Error: property "padding" must be followed by a ':'
+        on line #{line} of #{filename}
+>>   padding top: 10px;
+   --^
+        ERROR
+      rescue SassC::SyntaxError => err
+        expected = "#{Pathname.getwd.join(filename)}:#{line}"
+        assert_equal expected, err.backtrace.first
+      end
+    end
+  end
+end

From e8a1c7abd6e283e0a6133ab8e6612bd3fbfb7c9e Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashi-kokubun@cookpad.com>
Date: Thu, 28 Jan 2016 13:22:10 +0900
Subject: [PATCH 2/2] Don't hardcode line_info line number

---
 lib/sassc/error.rb |  6 ++++--
 test/error_test.rb | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/sassc/error.rb b/lib/sassc/error.rb
index 0c90b1c0..3f126e00 100644
--- a/lib/sassc/error.rb
+++ b/lib/sassc/error.rb
@@ -11,6 +11,8 @@ class UnsupportedValue < BaseError; end
   # it's important to provide filename and line number information.
   # This will be used in various error reports to users, including backtraces;
   class SyntaxError < BaseError
+    LINE_INFO_REGEX = /on line (\d+) of (.+)/
+
     def backtrace
       return nil if super.nil?
       sass_backtrace + super
@@ -18,10 +20,10 @@ def backtrace
 
     # The backtrace of the error within Sass files.
     def sass_backtrace
-      line_info = message.split("\n")[1]
+      line_info = message.split("\n").find { |line| line.match(LINE_INFO_REGEX) }
       return [] unless line_info
 
-      _, line, filename = line_info.match(/on line (\d+) of (.+)/).to_a
+      _, line, filename = line_info.match(LINE_INFO_REGEX).to_a
       ["#{Pathname.getwd.join(filename)}:#{line}"]
     end
   end
diff --git a/test/error_test.rb b/test/error_test.rb
index 20fd0b0a..844dc886 100644
--- a/test/error_test.rb
+++ b/test/error_test.rb
@@ -17,6 +17,21 @@ def test_first_backtrace_is_sass
         expected = "#{Pathname.getwd.join(filename)}:#{line}"
         assert_equal expected, err.backtrace.first
       end
+
+      begin
+        raise SassC::SyntaxError.new(<<-ERROR)
+Error: no mixin named border-radius
+
+       Backtrace:
+       \t#{filename}:#{line}
+        on line #{line} of #{filename}
+>>     @include border-radius(5px);
+   -------------^
+        ERROR
+      rescue SassC::SyntaxError => err
+        expected = "#{Pathname.getwd.join(filename)}:#{line}"
+        assert_equal expected, err.backtrace.first
+      end
     end
   end
 end