[experimental] Custom cop for detecting missing select

.rubocop.yml

@@ -1,7 +1,13 @@
+require:
+  - ./lib/rubocop/cop/custom/explicit_select.rb
+
+Custom/ExplicitSelect:
+  Enabled: true
+
 AllCops:
-  NewCops: enable
   Exclude:
     - "db/schema.rb"
+    - "db/migrate.rb"
     - "db/structure.sql"
     - "Gemfile"
     - "lib/tasks/*.rake"
@@ -11,9 +17,13 @@ AllCops:
     - "config/environments/development.rb"
     - "config/environments/production.rb"
     - "spec/spec_helper.rb"
+    - 'tmp/**/*'
+    - 'docker/**/*'
+    - 'log/**/*'
+    - '.circleci/**/*'
+    - '.git/**/*'
+  SuggestExtensions: false
+  NewCops: enable
+
 Style/Documentation:
   Enabled: false
-
-# Disable suggestions for rubocop-rails for now
-AllCops:
-  SuggestExtensions: false

README.md

@@ -203,3 +203,13 @@ bin/rails server
 Once that's running, visit <http://localhost:3000/pghero> in your browser to see it.
 
 ![Screenshot of PgHero for Rideshare](https://i.imgur.com/VduvxSK.png)
+
+## Rubocop
+
+- <https://danielabaron.me/blog/add-rubocop-to-legacy-project/>
+- Custom cop for detecting missing explicit select
+
+```
+app/controllers/api/trip_requests_controller.rb:3:5: C: [Correctable] Custom/ExplicitSelect: Avoid using all without an explicit .select(...). Autocorrecting to .select(:id).
+    Driver.all
+```

lib/rubocop/cop/custom/explicit_select.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Custom
+      # This cop warns when Active Record queries use `all` or `where`
+      # without an explicit `.select(...)` clause.
+      # Autocorrects to `.select(:id)` which needs to be expanded to all fields needed
+      # by the developer.
+      class ExplicitSelect < Base
+        extend AutoCorrector
+
+        MSG = 'Avoid using `%<method>s` without an explicit `.select(...)`. Autocorrecting to `.select(:id)`.'
+
+        RESTRICT_ON_SEND = %i[all where].freeze
+
+        def on_send(node)
+          return unless inside_active_record_chain?(node)
+
+          if node.method?(:all) || node.method?(:select) || node.method?(:where)
+            unless select_present_in_chain?(node)
+              add_offense(node, message: format(MSG, method: node.method_name)) do |corrector|
+                append_select_id(corrector, node)
+              end
+            end
+          end
+        end
+
+        private
+
+        def inside_active_record_chain?(node)
+          # Only apply if the receiver is a constant (e.g., `User.all`)
+          node.receiver&.const_type?
+        end
+
+        def select_present_in_chain?(node)
+          visited = Set.new
+
+          while node
+            return true if node.method?(:select) && node.arguments.any?
+
+            # Avoid re-visiting the same node (paranoia guard)
+            break if visited.include?(node)
+            visited << node
+
+            # Walk up the chain safely
+            node = node.parent if node.parent&.send_type?
+            break unless node&.send_type?
+          end
+
+          false
+        end
+
+        def append_select_id(corrector, node)
+          insertion_point = node.source_range.end
+          corrector.insert_after(insertion_point, '.select(:id)') # Developer must add additional fields beyond :id
+        end
+      end
+    end
+  end
+end