Remove Kernel#caller hack and avoid exception throwing for metadata

Should close out #36

CHANGELOG.md

@@ -4,6 +4,7 @@
 *   Opal 0.10 support
 *   Arity checking enabled by default
 *   Dropped support for PhantomJS < 2.0
+*   Removed `Kernel#caller` monkey patch so test file/line metadata is only available if supplied via test metadata or for failures. Should improve performance since an exception isn't thrown for every test to gather the data
 
 ## 0.5.0 (2015-12-08)
 

README.md

@@ -266,8 +266,9 @@ RSpec.configure do |c|
   c.include TestMod
 end
 ```
-* Formatting
-  * Backtrace info on specs is buggy ([no Kernel::caller method in Opal](https://github.com/opal/opal/issues/894)), in Firefox w/ the browser runner, no backtraces show up with failed specs
+* Formatting/Reporting
+  * Specs will not have file path/line number information on them unless they are supplied from user metadata or they fail, see [this issue](https://github.com/opal/opal-rspec/issues/36)
+  * In Firefox w/ the browser runner, no backtraces show up with failed specs
   * Diffs are not yet available when objects do not meet expectations (diff-lcs gem dependency has not been dealt with yet in Opal)
 * Configuration
   * Not all RSpec runner options are supported yet

opal/opal/rspec/fixes/opal.rb

@@ -1,2 +1 @@
 require_relative 'opal/compatibility'
-require_relative 'opal/kernel'

opal/opal/rspec/fixes/rspec/core/metadata.rb

@@ -2,20 +2,19 @@ module ::RSpec::Core::Metadata
   class HashPopulator
     def populate_location_attributes
       backtrace = user_metadata.delete(:caller)
+      # Throwing exceptions to get code location is expensive, so use this if the user supplied it, otherwise
+      # keep empty stuff around so filter code does not crash
 
-      file_path, line_number = if backtrace
+      # might have an empty array from caller which file_path_and_line_number_from doesn't like
+      file_path, line_number = if backtrace && !backtrace.empty?
                                  file_path_and_line_number_from(backtrace)
-                                 # Opal 0.9 has a stub for this but it does not return anything
-                               # elsif block.respond_to?(:source_location)
-                               #   block.source_location
                                else
-                                 file_path_and_line_number_from(caller)
+                                 ['', -1]
                                end
 
-      file_path = Metadata.relative_path(file_path)
-      metadata[:file_path] = file_path
+      metadata[:file_path]   = file_path
       metadata[:line_number] = line_number.to_i
-      metadata[:location] = "#{file_path}:#{line_number}"
+      metadata[:location]    = file_path.empty? ? '' : "#{file_path}:#{line_number}"
     end
   end
 end