Upgrade json gem, handle differences

This upgrades the `json` gem but by default maintains the old way
of handling parsing as this is relied upon in a few places. This
also adds support for a `legacy_mode` flag when parsing, which will
be added manually to areas that require this in future. Currently
the legacy_mode is the default.

Gemfile

@@ -496,3 +496,6 @@ gem 'lockbox', '~> 0.3.3'
 
 # Email validation
 gem 'valid_email', '~> 0.1'
+
+# JSON
+gem 'json', '~> 2.3.0'

Gemfile.lock

@@ -555,7 +555,7 @@ GEM
       character_set (~> 1.1)
       regexp_parser (~> 1.1)
       regexp_property_values (~> 0.3)
-    json (1.8.6)
+    json (2.3.0)
     json-jwt (1.11.0)
       activesupport (>= 4.2)
       aes_key_wrap
@@ -1280,6 +1280,7 @@ DEPENDENCIES
   invisible_captcha (~> 0.12.1)
   jira-ruby (~> 2.0.0)
   js_regex (~> 3.1)
+  json (~> 2.3.0)
   json-schema (~> 2.8.0)
   jwt (~> 2.1.0)
   kaminari (~> 1.0)

spec/lib/gitlab/json_spec.rb

@@ -17,18 +17,16 @@ RSpec.describe Gitlab::Json do
         expect(subject.parse('[{ "foo": "bar" }]')).to eq([{ "foo" => "bar" }])
       end
 
-      # These tests will change expectations when the gem is upgraded
-
-      it "raises an error on a string" do
-        expect { subject.parse('"foo"') }.to raise_error(JSON::ParserError)
+      it "parses a string" do
+        expect(subject.parse('"foo"', legacy_mode: false)).to eq("foo")
       end
 
-      it "raises an error on a true bool" do
-        expect { subject.parse("true") }.to raise_error(JSON::ParserError)
+      it "parses a true bool" do
+        expect(subject.parse("true", legacy_mode: false)).to be(true)
       end
 
-      it "raises an error on a false bool" do
-        expect { subject.parse("false") }.to raise_error(JSON::ParserError)
+      it "parses a false bool" do
+        expect(subject.parse("false", legacy_mode: false)).to be(false)
       end
     end
 
@@ -53,6 +51,32 @@ RSpec.describe Gitlab::Json do
         expect { subject.parse("false", legacy_mode: true) }.to raise_error(JSON::ParserError)
       end
     end
+
+    context "feature flag is disabled" do
+      before do
+        stub_feature_flags(json_wrapper_legacy_mode: false)
+      end
+
+      it "parses an object" do
+        expect(subject.parse('{ "foo": "bar" }', legacy_mode: true)).to eq({ "foo" => "bar" })
+      end
+
+      it "parses an array" do
+        expect(subject.parse('[{ "foo": "bar" }]', legacy_mode: true)).to eq([{ "foo" => "bar" }])
+      end
+
+      it "parses a string" do
+        expect(subject.parse('"foo"', legacy_mode: true)).to eq("foo")
+      end
+
+      it "parses a true bool" do
+        expect(subject.parse("true", legacy_mode: true)).to be(true)
+      end
+
+      it "parses a false bool" do
+        expect(subject.parse("false", legacy_mode: true)).to be(false)
+      end
+    end
   end
 
   describe ".parse!" do
@@ -65,18 +89,16 @@ RSpec.describe Gitlab::Json do
         expect(subject.parse!('[{ "foo": "bar" }]')).to eq([{ "foo" => "bar" }])
       end
 
-      # These tests will change expectations when the gem is upgraded
-
-      it "raises an error on a string" do
-        expect { subject.parse!('"foo"') }.to raise_error(JSON::ParserError)
+      it "parses a string" do
+        expect(subject.parse!('"foo"', legacy_mode: false)).to eq("foo")
       end
 
-      it "raises an error on a true bool" do
-        expect { subject.parse!("true") }.to raise_error(JSON::ParserError)
+      it "parses a true bool" do
+        expect(subject.parse!("true", legacy_mode: false)).to be(true)
       end
 
-      it "raises an error on a false bool" do
-        expect { subject.parse!("false") }.to raise_error(JSON::ParserError)
+      it "parses a false bool" do
+        expect(subject.parse!("false", legacy_mode: false)).to be(false)
       end
     end
 
@@ -101,6 +123,32 @@ RSpec.describe Gitlab::Json do
         expect { subject.parse!("false", legacy_mode: true) }.to raise_error(JSON::ParserError)
       end
     end
+
+    context "feature flag is disabled" do
+      before do
+        stub_feature_flags(json_wrapper_legacy_mode: false)
+      end
+
+      it "parses an object" do
+        expect(subject.parse!('{ "foo": "bar" }', legacy_mode: true)).to eq({ "foo" => "bar" })
+      end
+
+      it "parses an array" do
+        expect(subject.parse!('[{ "foo": "bar" }]', legacy_mode: true)).to eq([{ "foo" => "bar" }])
+      end
+
+      it "parses a string" do
+        expect(subject.parse!('"foo"', legacy_mode: true)).to eq("foo")
+      end
+
+      it "parses a true bool" do
+        expect(subject.parse!("true", legacy_mode: true)).to be(true)
+      end
+
+      it "parses a false bool" do
+        expect(subject.parse!("false", legacy_mode: true)).to be(false)
+      end
+    end
   end
 
   describe ".dump" do