Add new Rails/JSONSymbolizeNames cop

I've seen this pattern a lot: ```ruby JSON.parse(large_json).deep_symbolize_keys ``` instead of travesing Ruby hash once more we can use the `symbolize_names` option: ```ruby JSON.parse(large_json, symbolize_names: true) ``` Caveats / FP scenarios: 1. `symbolize_names` does not work if `create_addition` option is provided. 2. User might use both `symbolize_names: false` and `deep_symbolize_keys`. 3. There's no autocorrection yet, but it should be easy to add.

Author: viralpraxis

changelog/add_new_json_symbolize_names_cop.md

@@ -0,0 +1 @@
+* [#1532](https://github.com/rubocop/rubocop-rails/pull/1532): Add new `Rails/JSONSymbolizeNames` cop. ([@viralpraxis][])

config/default.yml

@@ -682,6 +682,11 @@ Rails/InverseOf:
  Include:
  - '**/app/models/**/*.rb'
 
+Rails/JSONSymbolizeNames:
+ Description: 'Use `JSON.parse(json, symbolize_names: true)` instead of `JSON.parse(json).deep_symbolize_keys`.'
+ Enabled: pending
+ VersionAdded: '<<next>>'
+
 Rails/LexicallyScopedActionFilter:
  Description: "Checks that methods specified in the filter's `only` or `except` options are explicitly defined in the class."
  StyleGuide: 'https://rails.rubystyle.guide#lexically-scoped-action-filter'

lib/rubocop/cop/rails/json_symbolize_names.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module RuboCop
+ module Cop
+ module Rails
+ # Use `JSON.parse(json, symbolize_names: true)` instead of `JSON.parse(json).deep_symbolize_keys`.
+
+ # Using `symbolize_names: true` is more efficient as it creates symbols during parsing
+ # rather than requiring a second pass through the data structure.
+
+ # @example
+ # # bad
+ # JSON.parse(json).deep_symbolize_keys
+ #
+ # # good
+ # JSON.parse(json, symbolize_names: true)
+ #
+ class JSONSymbolizeNames < Base
+ MSG = 'Use `symbolize_names` option.'
+
+ RESTRICT_ON_SEND = %i[deep_symbolize_keys].to_set.freeze
+
+ JSON_PARSING_METHOD_NAMES = %i[load_file load_file! parse parse!].to_set.freeze
+
+ # @!method deep_symbolize_keys?(node)
+ def_node_matcher :deep_symbolize_keys?, <<~PATTERN
+ (call
+ (send (const {nil? cbase} :JSON) JSON_PARSING_METHOD_NAMES ...) :deep_symbolize_keys)
+ PATTERN
+
+ def on_send(node)
+ deep_symbolize_keys?(node) do
+ add_offense(node)
+ end
+ end
+ alias on_csend on_send
+ end
+ end
+ end
+end

lib/rubocop/cop/rails_cops.rb

@@ -75,6 +75,7 @@
 require_relative 'rails/index_with'
 require_relative 'rails/inquiry'
 require_relative 'rails/inverse_of'
+require_relative 'rails/json_symbolize_names'
 require_relative 'rails/lexically_scoped_action_filter'
 require_relative 'rails/link_to_blank'
 require_relative 'rails/mailer_name'

spec/rubocop/cop/rails/json_symbolize_names_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Rails::JSONSymbolizeNames, :config do
+ %i[load_file load_file! parse parse!].each do |method_name|
+ context "with `#{method_name}` method" do
+ it "registers an offense for `JSON.#{method_name}` followed by `deep_symbolize_keys`" do
+ expect_offense(<<~RUBY, method_name: method_name)
+ JSON.#{method_name}(json).deep_symbolize_keys
+ ^^^^^^{method_name}^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `symbolize_names` option.
+ RUBY
+ end
+
+ it "registers an offense for `::JSON.#{method_name}` followed by `deep_symbolize_keys`" do
+ expect_offense(<<~RUBY, method_name: method_name)
+ ::JSON.#{method_name}(json).deep_symbolize_keys
+ ^^^^^^^^{method_name}^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `symbolize_names` option.
+ RUBY
+ end
+
+ it "registers an offense for `::JSON.#{method_name}` followed by `deep_symbolize_keys` with safe navigation" do
+ expect_offense(<<~RUBY, method_name: method_name)
+ ::JSON.#{method_name}("null")&.deep_symbolize_keys
+ ^^^^^^^^{method_name}^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `symbolize_names` option.
+ RUBY
+ end
+
+ it "does not register for `JSON.#{method_name}` with `symbolize_names` option" do
+ expect_no_offenses(<<~RUBY)
+ JSON.#{method_name}(json, symbolize_names: true)
+ RUBY
+ end
+
+ it "does not register for single `JSON.#{method_name}`" do
+ expect_no_offenses(<<~RUBY)
+ JSON.#{method_name}(json)
+ RUBY
+ end
+ end
+ end
+end