truncator: fix circular references

CHANGELOG.md

@@ -3,6 +3,10 @@ Airbrake Ruby Changelog
 
 ### master
 
+* Fixed circular references in the new truncator
+  ([#286](https://github.com/airbrake/airbrake-ruby/pull/286)). All v2.6.0 users
+  are *highly recommended* to upgrade.
+
 ### [v2.6.0][v2.6.0] (November 9, 2017)
 
 * Reworked truncation to not mutate given payload (params) and made it freeze it

lib/airbrake-ruby/truncator.rb

@@ -12,6 +12,15 @@ class Truncator
     #   strings with +ENCODING_OPTIONS+
     TEMP_ENCODING = 'utf-16'.freeze
 
+    # @return [String] what to append when something is a circular reference
+    CIRCULAR = '[Circular]'.freeze
+
+    # @return [String] what to append when something is truncated
+    TRUNCATED = '[Truncated]'.freeze
+
+    # @return [Array<Class>] The types that can contain references to itself
+    CIRCULAR_TYPES = [Array, Hash, Set].freeze
+
     # @param [Integer] max_size maximum size of hashes, arrays and strings
     def initialize(max_size)
       @max_size = max_size
@@ -24,7 +33,10 @@ def initialize(max_size)
     # @param [Set] seen The cache that helps to detect recursion
     # @return [Object] truncated object
     def truncate(object, seen = Set.new)
-      return '[Circular]'.freeze if seen.include?(object)
+      if seen.include?(object)
+        return CIRCULAR if CIRCULAR_TYPES.any? { |t| object.is_a?(t) }
+        return object
+      end
       truncate_object(object, seen << object)
     end
 
@@ -51,7 +63,7 @@ def truncate_object(object, seen)
     def truncate_string(str)
       fixed_str = replace_invalid_characters(str)
       return fixed_str if fixed_str.length <= @max_size
-      (fixed_str.slice(0, @max_size) + '[Truncated]').freeze
+      (fixed_str.slice(0, @max_size) + TRUNCATED).freeze
     end
 
     def stringify_object(object)

spec/truncator_spec.rb

@@ -211,5 +211,28 @@ def obj.to_json
         expect(subject).to be_frozen
       end
     end
+
+    context "given an array with hashes and hash-like objects with identical keys" do
+      let(:hashie) { Class.new(Hash) }
+
+      let(:object) do
+        {
+          errors: [
+            { file: 'a' },
+            hashie.new.merge(file: 'bcde')
+          ]
+        }
+      end
+
+      it "truncates values" do
+        expect(subject).to eq(
+          errors: [
+            { file: 'a' },
+            hashie.new.merge(file: 'bcd[Truncated]')
+          ]
+        )
+        expect(subject).to be_frozen
+      end
+    end
   end
 end