Performance/FlatMap does not work with block_pass #70
Description
Expected behavior
Given a test file test.rb:
# frozen_string_literal: true
# 1.
p [1, 2, 3].map { |x| x.digits }.flatten(1)
# 2.
p [1, 2, 3].map(&:digits).flatten(1)
# 3.
digits = proc { |x| x.digits }
p [1, 2, 3].map(&digits).flatten(1)I would expect RuboCop to suggest flat_map for 1., 2., and 3.
Output:
Details
Inspecting 1 file
C
Offenses:
test.rb:3:13: C: Performance/FlatMap: Use flat_map instead of map...flatten.
p [1, 2, 3].map { |x| x.digits }.flatten(1)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
test.rb:3:17: C: Style/SymbolProc: Pass &:digits as an argument to map instead of a block.
p [1, 2, 3].map { |x| x.digits }.flatten(1)
^^^^^^^^^^^^^^^^
test.rb:4:13: C: Performance/FlatMap: Use flat_map instead of map...flatten.
p [1, 2, 3].map(&:digits).flatten(1)
^^^^^^^^^^^^^^^^^^^^^^^^
test.rb:7:13: C: Performance/FlatMap: Use flat_map instead of map...flatten.
p [1, 2, 3].map(&digits).flatten(1)
^^^^^^^^^^^^^^^^^^^^^^^
1 file inspected, 4 offenses detected
Actual behavior
RuboCop only suggests flat_map for 1.
Output:
Details
Inspecting 1 file
C
Offenses:
test.rb:3:13: C: Performance/FlatMap: Use flat_map instead of map...flatten.
p [1, 2, 3].map { |x| x.digits }.flatten(1)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
test.rb:3:17: C: Style/SymbolProc: Pass &:digits as an argument to map instead of a block.
p [1, 2, 3].map { |x| x.digits }.flatten(1)
^^^^^^^^^^^^^^^^
1 file inspected, 2 offenses detected
Steps to reproduce the problem
Run rubocop -C false test.rb
RuboCop version
rubocop -V
0.72.0 (using Parser 2.6.3.0, running on ruby 2.6.3 x86_64-linux)
Suggested solultion
This patch below works as expected.
diff --git a/lib/rubocop/cop/performance/flat_map.rb b/lib/rubocop/cop/performance/flat_map.rb
index c90932f71..b5b91876a 100644
--- a/lib/rubocop/cop/performance/flat_map.rb
+++ b/lib/rubocop/cop/performance/flat_map.rb
@@ -23,7 +23,14 @@ module RuboCop
'multiple levels.'
def_node_matcher :flat_map_candidate?, <<-PATTERN
- (send (block $(send _ ${:collect :map}) ...) ${:flatten :flatten!} $...)
+ (send
+ {
+ (block $(send _ ${:collect :map}) ...)
+ $(send _ ${:collect :map} (block_pass _))
+ }
+ ${:flatten :flatten!}
+ $...
+ )
PATTERN
def on_send(node)