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cb82f5f0a4
Previously I assumed it was useless, however I was wrong. The method is called by the reloader to give the illusion that the GC is precise. Meaning a class that will be unloaded is immediately made invisible without waiting for it to be garbage collected. This is easy to do up to Ruby 3.0 because `DescendantTracker` keeps a map of all tracked classes. However on 3.1 we need to use the inverse strategy, we keep a WeakMap of all the classes we cleared, and we filter the return value of `descendants` and `subclasses`. Since `clear` is private API and is only used when reloading is enabled, to reduce the performance impact in production mode, we entirely remove this behavior when `config.cache_classes` is enabled.
106 lines
3.3 KiB
Ruby
106 lines
3.3 KiB
Ruby
# frozen_string_literal: true
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require_relative "abstract_unit"
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require "set"
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require "active_support/descendants_tracker"
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class DescendantsTrackerTest < ActiveSupport::TestCase
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setup do
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if ActiveSupport::DescendantsTracker.class_variable_defined?(:@@direct_descendants)
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@original_state = ActiveSupport::DescendantsTracker.class_variable_get(:@@direct_descendants).dup
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@original_state.each { |k, v| @original_state[k] = v.dup }
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end
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eval <<~RUBY
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class Parent
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extend ActiveSupport::DescendantsTracker
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end
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class Child1 < Parent
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end
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class Child2 < Parent
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end
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class Grandchild1 < Child1
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end
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class Grandchild2 < Child1
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end
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RUBY
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end
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teardown do
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if ActiveSupport::DescendantsTracker.class_variable_defined?(:@@direct_descendants)
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ActiveSupport::DescendantsTracker.class_variable_get(:@@direct_descendants).replace(@original_state)
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end
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%i(Parent Child1 Child2 Grandchild1 Grandchild2).each do |name|
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if DescendantsTrackerTest.const_defined?(name)
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DescendantsTrackerTest.send(:remove_const, name)
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end
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end
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end
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test ".descendants" do
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assert_equal_sets [Child1, Grandchild1, Grandchild2, Child2], Parent.descendants
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assert_equal_sets [Grandchild1, Grandchild2], Child1.descendants
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assert_equal_sets [], Child2.descendants
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end
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test ".descendants with garbage collected classes" do
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# The Ruby GC (and most other GCs for that matter) are not fully precise.
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# When GC is run, the whole stack is scanned to mark any object reference
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# in registers. But some of these references might simply be leftovers from
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# previous method calls waiting to be overridden, and there's no definite
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# way to clear them. By executing this code in a distinct thread, we ensure
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# that such references are on a stack that will be entirely garbage
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# collected, effectively working around the problem.
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Thread.new do
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child_klass = Class.new(Parent)
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assert_equal_sets [Child1, Grandchild1, Grandchild2, Child2, child_klass], Parent.descendants
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end.join
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# Calling `GC.start` 4 times should trigger a full GC run
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4.times do
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GC.start
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end
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assert_equal_sets [Child1, Grandchild1, Grandchild2, Child2], Parent.descendants
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end
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test ".direct_descendants" do
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assert_deprecated do
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assert_equal_sets [Child1, Child2], Parent.direct_descendants
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end
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assert_deprecated do
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assert_equal_sets [Grandchild1, Grandchild2], Child1.direct_descendants
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end
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assert_deprecated do
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assert_equal_sets [], Child2.direct_descendants
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end
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end
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test ".subclasses" do
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[Parent, Child1, Child2].each do |klass|
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assert_equal assert_deprecated { klass.direct_descendants }, klass.subclasses
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end
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end
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test ".clear(classes) deletes the given classes only" do
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ActiveSupport::DescendantsTracker.clear(Set[Child2, Grandchild1])
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assert_equal_sets [Child1, Grandchild2], Parent.descendants
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assert_equal_sets [Grandchild2], Child1.descendants
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assert_equal_sets [Child1], assert_deprecated { Parent.direct_descendants }
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assert_equal_sets [Grandchild2], assert_deprecated { Child1.direct_descendants }
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end
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private
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def assert_equal_sets(expected, actual)
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assert_equal Set.new(expected), Set.new(actual)
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end
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end
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