test on old json, fix old rubocop config

Author: uvlad7

.rubocop.yml

@@ -42,3 +42,9 @@ Style/TrailingCommaInHashLiteral:
 
 Lint/RedundantCopDisableDirective:
   Enabled: false
+
+Metrics/AbcSize:
+  Max: 17
+
+Bundler/DuplicatedGem:
+  Enabled: false

Gemfile

@@ -49,4 +49,8 @@ if RUBY_VERSION >= "2.7"
   gem "yajl-ruby", "~> 1.4"
 end
 
+# test on the oldest version of the json gem we can expect based on the required_ruby_version
+# see https://stdgems.org/compare/2.3/
+gem "json", "1.8.3.1" if RUBY_VERSION < "2.4"
+
 gem "libyajl2", "~> 2.1"

Gemfile_ruby_2_3.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     json_scanner (0.3.1)
-      json
+      json (>= 1.8.3.1)
 
 GEM
   remote: https://rubygems.org/
@@ -12,7 +12,7 @@ GEM
     coderay (1.1.3)
     diff-lcs (1.5.1)
     jaro_winkler (1.5.6)
-    json (2.7.6)
+    json (1.8.3.1)
     libyajl2 (2.1.0)
     method_source (0.9.2)
     parallel (1.19.2)
@@ -61,6 +61,7 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  json (= 1.8.3.1)
   json_scanner!
   libyajl2 (~> 2.1)
   pry (~> 0.12.2)

json_scanner.gemspec

@@ -29,5 +29,5 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
   spec.extensions = ["ext/json_scanner/extconf.rb"]
   spec.metadata["rubygems_mfa_required"] = "true"
-  spec.add_dependency "json"
+  spec.add_dependency "json", ">= 1.8.3.1"
 end