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author | Matthew Draper <matthew@trebex.net> | 2018-02-24 17:04:15 +1030 |
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committer | Matthew Draper <matthew@trebex.net> | 2018-02-24 17:15:32 +1030 |
commit | 17ca17072dcdff11b3702a6b45f2fb0c8f8fe9a4 (patch) | |
tree | 38afd3ed74f8afda1c2959fefbc13f70b2e448e2 /activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb | |
parent | 5ecbeda0e225e4961977b5c516088cf12d92319f (diff) | |
parent | eb3f968b5ffdd3b343e7d190f1aa0b36864f56a2 (diff) | |
download | rails-17ca17072dcdff11b3702a6b45f2fb0c8f8fe9a4.tar.gz rails-17ca17072dcdff11b3702a6b45f2fb0c8f8fe9a4.tar.bz2 rails-17ca17072dcdff11b3702a6b45f2fb0c8f8fe9a4.zip |
Merge Arel into Active Record
Diffstat (limited to 'activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb')
-rw-r--r-- | activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb b/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb new file mode 100644 index 0000000000..eb278cde4c --- /dev/null +++ b/activerecord/test/cases/arel/visitors/dispatch_contamination_test.rb @@ -0,0 +1,72 @@ +# frozen_string_literal: true +require_relative '../helper' +require 'concurrent' + +module Arel + module Visitors + class DummyVisitor < Visitor + def initialize + super + @barrier = Concurrent::CyclicBarrier.new(2) + end + + def visit_Arel_Visitors_DummySuperNode node + 42 + end + + # This is terrible, but it's the only way to reliably reproduce + # the possible race where two threads attempt to correct the + # dispatch hash at the same time. + def send *args + super + rescue + # Both threads try (and fail) to dispatch to the subclass's name + @barrier.wait + raise + ensure + # Then one thread successfully completes (updating the dispatch + # table in the process) before the other finishes raising its + # exception. + Thread.current[:delay].wait if Thread.current[:delay] + end + end + + class DummySuperNode + end + + class DummySubNode < DummySuperNode + end + + class DispatchContaminationTest < Arel::Spec + before do + @connection = Table.engine.connection + @table = Table.new(:users) + end + + it 'dispatches properly after failing upwards' do + node = Nodes::Union.new(Nodes::True.new, Nodes::False.new) + assert_equal "( TRUE UNION FALSE )", node.to_sql + + node.first # from Nodes::Node's Enumerable mixin + + assert_equal "( TRUE UNION FALSE )", node.to_sql + end + + it 'is threadsafe when implementing superclass fallback' do + visitor = DummyVisitor.new + main_thread_finished = Concurrent::Event.new + + racing_thread = Thread.new do + Thread.current[:delay] = main_thread_finished + visitor.accept DummySubNode.new + end + + assert_equal 42, visitor.accept(DummySubNode.new) + main_thread_finished.set + + assert_equal 42, racing_thread.value + end + end + end +end + |