Fixed Thread::Backtrace::Location#path.

Location#path isn't an alias, nor does it always return an absolute path.
Instead, if it's called in the main script and the path to said script is
relative _then_ Location#path gives a relative path. In all other cases it gives
back an absolute path.

Lets hope we now implemented it properly. Something something if MRI had clear
tests this would've been far easier.

Fixes #3310.

Author: Yorick Peterse

kernel/common/kernel.rb

@@ -282,11 +282,12 @@ def caller_locations(start = 1, length = nil)
         break
       end
 
-      locations << Thread::Backtrace::Location.new(
-        tup[3].to_s,
-        tup[0].active_path,
-        tup[1]
-      )
+      scope    = tup[0].scope
+      abs_path = tup[0].active_path
+      path     = scope ? scope.active_path : abs_path
+      label    = tup[3].to_s
+
+      locations << Thread::Backtrace::Location.new(label, abs_path, path, tup[1])
     end
 
     locations

kernel/common/thread.rb

@@ -140,17 +140,18 @@ class Backtrace
     # Stores location of a single call frame, available since Ruby 2.0.
     class Location
       attr_reader :label
+      attr_reader :path
       attr_reader :absolute_path
       attr_reader :lineno
 
-      def initialize(label, absolute_path, lineno)
+      def initialize(label, absolute_path, path, lineno)
         @label         = label
         @absolute_path = absolute_path
+        @path          = path
         @lineno        = lineno
       end
 
       alias_method :base_label, :label
-      alias_method :path, :absolute_path
 
       def to_s
         "#{absolute_path}:#{lineno}:in `#{label}'"

spec/ruby/core/thread/backtrace/location/fixtures/main.rb

@@ -0,0 +1,5 @@
+def example
+  caller_locations[0].path
+end
+
+print example

spec/ruby/core/thread/backtrace/location/path_spec.rb

@@ -2,11 +2,83 @@
 require File.expand_path('../fixtures/classes', __FILE__)
 
 describe 'Thread::Backtrace::Location#path' do
-  before :each do
-    @frame = ThreadBacktraceLocationSpecs.locations[0]
+  context 'outside a main script' do
+    it 'returns an absolute path' do
+      frame = ThreadBacktraceLocationSpecs.locations[0]
+
+      frame.path.should == __FILE__
+    end
   end
 
-  it 'returns the absolute path of the call frame' do
-    @frame.path.should == __FILE__
+  context 'in a main script' do
+    before do
+      @script = fixture(__FILE__, 'main.rb')
+    end
+
+    context 'when the script is in the working directory' do
+      before do
+        @directory = File.dirname(@script)
+      end
+
+      context 'when using a relative script path' do
+        it 'returns a path relative to the working directory' do
+          ruby_exe('main.rb', :dir => @directory).should == 'main.rb'
+        end
+      end
+
+      context 'when using an absolute script path' do
+        it 'returns an absolute path' do
+          ruby_exe(@script, :dir => @directory).should == @script
+        end
+      end
+    end
+
+    context 'when the script is in a sub directory of the working directory' do
+      context 'when using a relative script path' do
+        it 'returns a path relative to the working directory' do
+          path      = 'fixtures/main.rb'
+          directory = File.dirname(__FILE__)
+
+          ruby_exe(path, :dir => directory).should == path
+        end
+      end
+
+      context 'when using an absolute script path' do
+        it 'returns an absolute path' do
+          ruby_exe(@script).should == @script
+        end
+      end
+    end
+
+    context 'when the script is outside of the working directory' do
+      before do
+        @parent_dir = tmp('path_outside_pwd')
+        @sub_dir    = File.join(@parent_dir, 'sub')
+        @script     = File.join(@parent_dir, 'main.rb')
+        source      = fixture(__FILE__, 'main.rb')
+
+        mkdir_p(@sub_dir)
+
+        cp(source, @script)
+      end
+
+      after do
+        rm_r(@script)
+        rm_r(@sub_dir)
+        rm_r(@parent_dir)
+      end
+
+      context 'when using a relative script path' do
+        it 'returns a path relative to the working directory' do
+          ruby_exe('../main.rb', :dir => @sub_dir).should == '../main.rb'
+        end
+      end
+
+      context 'when using an absolute path' do
+        it 'returns an absolute path' do
+          ruby_exe(@script).should == @script
+        end
+      end
+    end
   end
 end