Handle old and new backtrace format, fixes 1477

app/models/backtrace.rb

@@ -2,8 +2,8 @@ class Backtrace
   include Mongoid::Document
   include Mongoid::Timestamps
 
-  IN_APP_PATH = %r{^\[PROJECT_ROOT\](?!(\/vendor))/?}
-  GEMS_PATH = %r{\[GEM_ROOT\]\/gems\/([^\/]+)}
+  IN_APP_PATH = %r{^(?:\[|/)PROJECT_ROOT\]?(?!(/vendor))/?}
+  GEMS_PATH = %r{(?:\[|/)GEM_ROOT\]?/gems/([^/]+)}
 
   field :fingerprint
   field :lines

spec/decorators/backtrace_line_decorator_spec.rb

@@ -11,6 +11,12 @@
       file:   '[PROJECT_ROOT]/path/to/file/ea315ea4.rb',
       method: :instance_eval)
   end
+  let(:backtrace_line_in_app_slashes) do
+    described_class.new(
+      number: 884,
+      file:   '/PROJECT_ROOT/path/to/file/ea315ea4.rb',
+      method: :instance_eval)
+  end
   let(:backtrace_line_no_file) do
     described_class.new(number: 884, method: :instance_eval)
   end
@@ -47,6 +53,16 @@
     end
   end
 
+  describe '#decorated_path' do
+    it 'parses old backtrace format with square brackets' do
+      expect(backtrace_line_in_app.decorated_path).to eq 'path/to/file/'
+    end
+
+    it 'parses new backtrace format with slashes' do
+      expect(backtrace_line_in_app_slashes.decorated_path).to eq 'path/to/file/'
+    end
+  end
+
   describe '#link_to_source_file' do
     it 'adds a link to the source file' do
       link = backtrace_line_in_app.link_to_source_file(app) { 'mytext' }