Class: RuboCop::Cop::DevDoc::Migration::RedundantReferenceIndex

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Includes:
HashPairRemoval
Defined in:
lib/rubocop/cop/dev_doc/migration/redundant_reference_index.rb

Overview

Avoid the redundant index: true on references.

Rationale

belongs_to / references / add_reference default to index: true since Rails 5 — the index is created whether or not the option is written. An explicit index: true therefore does nothing except make every future reader wonder whether it does (and imply, wrongly, that references without it are unindexed).

The option is only meaningful when it overrides the default: index: false to opt out, or a hash to customize (index: { unique: true }). Those forms pass untouched.

❌ Redundant — this index exists anyway
t.belongs_to :user, foreign_key: true, null: false, index: true

✔️
t.belongs_to :user, foreign_key: true, null: false

✔️ Meaningful override
t.belongs_to :user, foreign_key: true, null: false, index: { unique: true }

NOTE: This cop removes the one reference option whose default is already correct; the sibling cops DevDoc/Migration/RequireReferenceForeignKey and DevDoc/Migration/ExplicitNullOnReference require the two options that ARE decisions to be made and stated. Together: everything written on a reference is a decision, everything omitted is doctrine.

NOTE: When a comment sits between the call's arguments, the cop flags the option but does not autocorrect (removing the range would corrupt the comment) — delete the option manually.

NOTE: Migrations declared < ActiveRecord::Migration[4.2] are skipped entirely: the 4.2 compatibility layer flips the reference default to index: false, so there index: true is meaningful — removing it would drop the index on a from-zero db:migrate.

Examples:

# bad
t.belongs_to :user, foreign_key: true, index: true

# good
t.belongs_to :user, foreign_key: true

# good (meaningful override)
t.belongs_to :user, foreign_key: true, index: { unique: true }

Constant Summary collapse

MSG = 
'`index: true` is redundant — references are indexed by default since Rails 5.'.freeze
RESTRICT_ON_SEND = 
%i[belongs_to references add_reference add_belongs_to].freeze

Instance Method Summary collapse

Instance Method Details

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/dev_doc/migration/redundant_reference_index.rb', line 63

def on_send(node)
  options = node.arguments.find(&:hash_type?)
  return unless options
  return if legacy_migration?(node)

  options.pairs.each { |pair| check_pair(node, options, pair) }
end