Merge pull request #206 from rollbar/add-backtrace-to-exceptions

Add backtrace to exceptions without backtrace. Closes #205.

Gemfile

@@ -12,3 +12,9 @@ gem 'racc',                             :platform => :rbx
 gem 'minitest',                         :platform => :rbx
 gem 'rubysl-test-unit',                 :platform => :rbx
 gem 'rubinius-developer_tools',         :platform => :rbx
+
+if RUBY_VERSION.chars.first.to_i > 1
+  gem 'byebug'
+else
+  gem 'debugger'
+end

README.md

@@ -379,6 +379,23 @@ Rollbar.silenced {
 }
 ```
 
+# Sending backtrace without rescued exceptions
+
+If you use the gem in this way:
+
+```ruby
+exception = MyException.new('this is a message')
+Rollbar.error(exception)
+```
+
+You will notice a backtrace doesn't appear in your Rollbar dashboard. This is because `exception.backtrace` is `nil` in these cases. We can send the current backtrace for you even your exception doesn't have it. In order to enable this feature you should configure Rollbar in this way:
+
+```ruby
+Rollbar.configure do |config|
+  config.populate_empty_backtraces = true
+end
+```
+
 ## Delayed::Job integration
 
 If `delayed_job` is defined, Rollbar will automatically install a plugin that reports any uncaught exceptions that occur in jobs.

lib/rollbar.rb

@@ -339,23 +339,20 @@ def build_payload_body_exception(message, exception, extra)
     end
 
     def trace_data(exception)
-      # parse backtrace
-      if exception.backtrace.respond_to?( :map )
-        frames = exception.backtrace.map { |frame|
-          # parse the line
-          match = frame.match(/(.*):(\d+)(?::in `([^']+)')?/)
-          if match
-            { :filename => match[1], :lineno => match[2].to_i, :method => match[3] }
-          else
-            { :filename => "<unknown>", :lineno => 0, :method => frame }
-          end
-        }
-        # reverse so that the order is as rollbar expects
-        frames.reverse!
-      else
-        frames = []
+      frames = exception_backtrace(exception).map do |frame|
+        # parse the line
+        match = frame.match(/(.*):(\d+)(?::in `([^']+)')?/)
+
+        if match
+          { :filename => match[1], :lineno => match[2].to_i, :method => match[3] }
+        else
+          { :filename => "<unknown>", :lineno => 0, :method => frame }
+        end
       end
 
+        # reverse so that the order is as rollbar expects
+      frames.reverse!
+
       {
         :frames => frames,
         :exception => {
@@ -365,6 +362,28 @@ def trace_data(exception)
       }
     end
 
+    # Returns the backtrace to be sent to our API. There are 3 options:
+    #
+    # 1. The exception received has a backtrace, then that backtrace is returned.
+    # 2. configuration.populate_empty_backtraces is disabled, we return [] here
+    # 3. The user has configuration.populate_empty_backtraces is enabled, then:
+    #
+    # We want to send the caller as backtrace, but the first lines of that array
+    # are those from the user's Rollbar.error line until this method. We want
+    # to remove those lines.
+    def exception_backtrace(exception)
+      return exception.backtrace if exception.backtrace.respond_to?( :map )
+      return [] unless configuration.populate_empty_backtraces
+
+      caller_backtrace = caller
+      caller_backtrace.shift while caller_backtrace[0].include?(rollbar_lib_gem_dir)
+      caller_backtrace
+    end
+
+    def rollbar_lib_gem_dir
+      Gem::Specification.find_by_name('rollbar').gem_dir + '/lib'
+    end
+
     def trace_chain(exception)
       traces = [trace_data(exception)]
       visited = [exception]

lib/rollbar/configuration.rb

@@ -26,6 +26,7 @@ class Configuration
     attr_accessor :person_id_method
     attr_accessor :person_username_method
     attr_accessor :person_email_method
+    attr_accessor :populate_empty_backtraces
     attr_accessor :report_dj_data
     attr_accessor :request_timeout
     attr_accessor :root
@@ -67,6 +68,7 @@ def initialize
       @person_username_method = 'username'
       @person_email_method = 'email'
       @project_gems = []
+      @populate_empty_backtraces = false
       @report_dj_data = true
       @request_timeout = 3
       @scrub_fields = [:passwd, :password, :password_confirmation, :secret,

spec/rollbar_spec.rb

@@ -879,6 +879,25 @@
       payload["data"][:body][:trace][:exception][:message].should == "oops"
     end
 
+    it 'gets the backtrace from the caller' do
+      Rollbar.configure do |config|
+        config.populate_empty_backtraces = true
+      end
+
+      exception = Exception.new
+
+      Rollbar.error(exception)
+
+      gem_dir = Gem::Specification.find_by_name('rollbar').gem_dir
+      gem_lib_dir = gem_dir + '/lib'
+      last_report = Rollbar.last_report
+
+      filepaths = last_report[:body][:trace][:frames].map {|frame| frame[:filename] }.reverse
+
+      expect(filepaths[0]).not_to include(gem_lib_dir)
+      expect(filepaths.any? {|filepath| filepath.include?(gem_dir) }).to be_true
+    end
+
     it 'should return the exception data with a uuid, on platforms with SecureRandom' do
       if defined?(SecureRandom) and SecureRandom.respond_to?(:uuid)
         exception_data = Rollbar.error(StandardError.new("oops"))