Class: RuboCop::Cop::Kaizo::PluralCollectionName

Inherits:
Base
  • Object
show all
Includes:
AllowedMethods
Defined in:
lib/rubocop/cop/kaizo/plural_collection_name.rb

Overview

Checks that a method returning a collection is named in the plural. A singular name on a method handing back an array (def user returning [first, second]) misdescribes what the caller gets; the plural does the documenting for free.

Ruby has no return types, so "returns an array" is a heuristic, and this cop deliberately errs toward silence. A method is only flagged when every value it can return is unambiguously an array: an array literal, or a call to a method that returns an Array whatever its receiver (ArrayMethods, e.g. map, to_a, sort). One branch returning nil is enough to leave the method alone. Methods like select and reject are absent by design -- on a Hash they hand back a Hash.

A name counts as plural when it ends in s or appears in IrregularPlurals. Predicate (?), writer (=), and operator methods are exempt, as is initialize, and AllowedMethods exempts names outright. There is no autocorrection: renaming a method is a design decision, and only its author knows the right plural.

Configuration

[+ArrayMethods+] Calls treated as returning an Array whatever their receiver. Default: map, flat_map, collect, collect_concat, to_a, entries, sort, sort_by, zip. [+IrregularPlurals+] Names accepted as plural despite not ending in s. Default: people, children, men, women, data, media, criteria. [+AllowedMethods+] Method names never flagged. Default: none.

Extend a list without restating its default via RuboCop's inherit_mode: merge:

Kaizo/PluralCollectionName:
inherit_mode:
  merge:
    - ArrayMethods
    - IrregularPlurals
ArrayMethods:
  - fetch_all
IrregularPlurals:
  - alumni

Examples:

# bad
def user
  [first_match, second_match]
end

# good
def users
  [first_match, second_match]
end
# good - not confidently an array, so not flagged
def user
  return nil if missing?

  [first_match, second_match]
end

Constant Summary collapse

MSG = 
"Name a method that returns a collection in the plural. " \
"`%<name>s` returns an array.".freeze
DEFAULT_ARRAY_METHODS =

Methods whose result is an Array regardless of the receiver. Kept deliberately short: anything whose return type follows its receiver (select on a Hash) would turn this cop into a false-positive mill.

%i[
  map flat_map collect collect_concat to_a entries sort sort_by zip
].freeze

Instance Method Summary collapse

Instance Method Details

#on_def(node) ⇒ Object Also known as: on_defs 



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# File 'lib/rubocop/cop/kaizo/plural_collection_name.rb', line 79

def on_def(node)
  return if exempt?(node)
  return unless returns_array?(node.body)

  add_offense(node.loc.name, message: format(MSG, name: node.method_name))
end