1 files changed, 823 insertions, 0 deletions
diff --git a/spec/ruby/core/module/prepend_spec.rb b/spec/ruby/core/module/prepend_spec.rb
new file mode 100644
index 0000000000..71e82c513e
--- /dev/null
+++ b/spec/ruby/core/module/prepend_spec.rb
@@ -0,0 +1,823 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Module#prepend" do
+  it "is a public method" do
+    Module.should have_public_instance_method(:prepend, false)
+  end
+
+  it "does not affect the superclass" do
+    Class.new { prepend Module.new }.superclass.should == Object
+  end
+
+  it "calls #prepend_features(self) in reversed order on each module" do
+    ScratchPad.record []
+
+    m = Module.new do
+      def self.prepend_features(mod)
+        ScratchPad << [ self, mod ]
+      end
+    end
+
+    m2 = Module.new do
+      def self.prepend_features(mod)
+        ScratchPad << [ self, mod ]
+      end
+    end
+
+    m3 = Module.new do
+      def self.prepend_features(mod)
+        ScratchPad << [ self, mod ]
+      end
+    end
+
+    c = Class.new { prepend(m, m2, m3) }
+
+    ScratchPad.recorded.should == [ [ m3, c], [ m2, c ], [ m, c ] ]
+  end
+
+  it "updates the method when a module is prepended" do
+    m_module = Module.new do
+      def foo
+        "m"
+      end
+    end
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+    a_class.class_eval do
+      prepend m_module
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a prepended module is updated" do
+    m_module = Module.new
+    a_class = Class.new do
+      prepend m_module
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the optimized method when a prepended module is updated" do
+    out = ruby_exe(<<~RUBY)
+    module M; end
+    class Integer
+      prepend M
+    end
+    l = -> { 1 + 2 }
+    p l.call
+    M.module_eval do
+      def +(o)
+        $called = true
+        super(o)
+      end
+    end
+    p l.call
+    p $called
+    RUBY
+    out.should == "3\n3\ntrue\n"
+  end
+
+  it "updates the method when there is a base included method and the prepended module overrides it" do
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new do
+      include base_module
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new do
+      def foo
+        "m"
+      end
+    end
+    a_class.prepend m_module
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when there is a base included method and the prepended module is later updated" do
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new do
+      include base_module
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new
+    a_class.prepend m_module
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a module prepended after a call is later updated" do
+    m_module = Module.new
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    a_class.prepend m_module
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a module is prepended after another and the method is defined later on that module" do
+    m_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new
+    a_class.prepend m_module
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    n_module = Module.new
+    a_class.prepend n_module
+    foo.call.should == 'a'
+
+    n_module.module_eval do
+      def foo
+        "n"
+      end
+    end
+    foo.call.should == 'n'
+  end
+
+  it "updates the method when a module is included in a prepended module and the method is defined later" do
+    a_class = Class.new
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class.prepend base_module
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new
+    n_module = Module.new
+    m_module.include n_module
+    a_class.prepend m_module
+
+    n_module.module_eval do
+      def foo
+        "n"
+      end
+    end
+    foo.call.should == 'n'
+  end
+
+  it "updates the method when a new module with an included module is prepended" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    n_module = Module.new do
+      def foo
+        'n'
+      end
+    end
+
+    m_module = Module.new  do
+      include n_module
+    end
+
+    a = a_class.new
+    foo = -> { a.foo }
+
+    foo.call.should == 'a'
+
+    a_class.class_eval do
+      prepend m_module
+    end
+
+    foo.call.should == 'n'
+  end
+
+  it "updates the constant when a module is prepended" do
+    module ModuleSpecs::ConstUpdatePrepended
+      module M
+        FOO = 'm'
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+      B.prepend M
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatePrepended)
+  end
+
+  it "updates the constant when a prepended module is updated" do
+    module ModuleSpecs::ConstPrependedUpdated
+      module M
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        prepend M
+        def self.foo
+          FOO
+        end
+      end
+      B.foo.should == 'a'
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstPrependedUpdated)
+  end
+
+  it "updates the constant when there is a base included constant and the prepended module overrides it" do
+    module ModuleSpecs::ConstIncludedPrependedOverride
+      module Base
+        FOO = 'a'
+      end
+      module A
+        include Base
+        def self.foo
+          FOO
+        end
+      end
+      A.foo.should == 'a'
+
+      module M
+        FOO = 'm'
+      end
+      A.prepend M
+      A.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstIncludedPrependedOverride)
+  end
+
+  it "updates the constant when there is a base included constant and the prepended module is later updated" do
+    module ModuleSpecs::ConstIncludedPrependedLaterUpdated
+      module Base
+        FOO = 'a'
+      end
+      module A
+        include Base
+        def self.foo
+          FOO
+        end
+      end
+      A.foo.should == 'a'
+
+      module M
+      end
+      A.prepend M
+      A.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      A.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstIncludedPrependedLaterUpdated)
+  end
+
+  it "updates the constant when a module prepended after a constant is later updated" do
+    module ModuleSpecs::ConstUpdatedPrependedAfterLaterUpdated
+      module M
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+      B.foo.should == 'a'
+
+      B.prepend M
+      B.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedPrependedAfterLaterUpdated)
+  end
+
+  it "updates the constant when a module is prepended after another and the constant is defined later on that module" do
+    module ModuleSpecs::ConstUpdatedPrependedAfterConstDefined
+      module M
+        FOO = 'm'
+      end
+      module A
+        prepend M
+        def self.foo
+          FOO
+        end
+      end
+
+      A.foo.should == 'm'
+
+      module N
+      end
+      A.prepend N
+      A.foo.should == 'm'
+
+      N.const_set(:FOO, 'n')
+      A.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedPrependedAfterConstDefined)
+  end
+
+  it "updates the constant when a module is included in a prepended module and the constant is defined later" do
+    module ModuleSpecs::ConstUpdatedIncludedInPrependedConstDefinedLater
+      module A
+        def self.foo
+          FOO
+        end
+      end
+      module Base
+        FOO = 'a'
+      end
+
+      A.prepend Base
+      A.foo.should == 'a'
+
+      module N
+      end
+      module M
+        include N
+      end
+
+      A.prepend M
+
+      N.const_set(:FOO, 'n')
+      A.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedIncludedInPrependedConstDefinedLater)
+  end
+
+  it "updates the constant when a new module with an included module is prepended" do
+    module ModuleSpecs::ConstUpdatedNewModuleIncludedPrepended
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+      module N
+        FOO = 'n'
+      end
+
+      module M
+        include N
+      end
+
+      B.foo.should == 'a'
+
+      B.prepend M
+      B.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedNewModuleIncludedPrepended)
+  end
+
+  it "raises a TypeError when the argument is not a Module" do
+    -> { ModuleSpecs::Basic.prepend(Class.new) }.should raise_error(TypeError)
+  end
+
+  it "does not raise a TypeError when the argument is an instance of a subclass of Module" do
+    class ModuleSpecs::SubclassSpec::AClass
+    end
+    -> { ModuleSpecs::SubclassSpec::AClass.prepend(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
+  ensure
+    ModuleSpecs::SubclassSpec.send(:remove_const, :AClass)
+  end
+
+  it "raises a TypeError when the argument is a refinement" do
+    refinement = nil
+
+    Module.new do
+      refine String do
+        refinement = self
+      end
+    end
+
+    -> { ModuleSpecs::Basic.prepend(refinement) }.should raise_error(TypeError, "Cannot prepend refinement")
+  end
+
+  it "imports constants" do
+    m1 = Module.new
+    m1::MY_CONSTANT = 1
+    m2 = Module.new { prepend(m1) }
+    m2.constants.should include(:MY_CONSTANT)
+  end
+
+  it "imports instance methods" do
+    Module.new { prepend ModuleSpecs::A }.instance_methods.should include(:ma)
+  end
+
+  it "does not import methods to modules and classes" do
+    Module.new { prepend ModuleSpecs::A }.methods.should_not include(:ma)
+  end
+
+  it "allows wrapping methods" do
+    m = Module.new { def calc(x) super + 3 end }
+    c = Class.new { def calc(x) x*2 end }
+    c.prepend(m)
+    c.new.calc(1).should == 5
+  end
+
+  it "also prepends included modules" do
+    a = Module.new { def calc(x) x end }
+    b = Module.new { include a }
+    c = Class.new { prepend b }
+    c.new.calc(1).should == 1
+  end
+
+  it "prepends multiple modules in the right order" do
+    m1 = Module.new { def chain; super << :m1; end }
+    m2 = Module.new { def chain; super << :m2; end; prepend(m1) }
+    c = Class.new { def chain; [:c]; end; prepend(m2) }
+    c.new.chain.should == [:c, :m2, :m1]
+  end
+
+  it "includes prepended modules in ancestors" do
+    m = Module.new
+    Class.new { prepend(m) }.ancestors.should include(m)
+  end
+
+  it "reports the prepended module as the method owner" do
+    m = Module.new { def meth; end }
+    c = Class.new { def meth; end; prepend(m) }
+    c.new.method(:meth).owner.should == m
+  end
+
+  it "reports the prepended module as the unbound method owner" do
+    m = Module.new { def meth; end }
+    c = Class.new { def meth; end; prepend(m) }
+    c.instance_method(:meth).owner.should == m
+    c.public_instance_method(:meth).owner.should == m
+  end
+
+  it "causes the prepended module's method to be aliased by alias_method" do
+    m = Module.new { def meth; :m end }
+    c = Class.new { def meth; :c end; prepend(m); alias_method :alias, :meth }
+    c.new.alias.should == :m
+  end
+
+  it "reports the class for the owner of an aliased method on the class" do
+    m = Module.new
+    c = Class.new { prepend(m); def meth; :c end; alias_method :alias, :meth }
+    c.instance_method(:alias).owner.should == c
+  end
+
+  it "reports the class for the owner of a method aliased from the prepended module" do
+    m = Module.new { def meth; :m end }
+    c = Class.new { prepend(m); alias_method :alias, :meth }
+    c.instance_method(:alias).owner.should == c
+  end
+
+  it "sees an instance of a prepended class as kind of the prepended module" do
+    m = Module.new
+    c = Class.new { prepend(m) }
+    c.new.should be_kind_of(m)
+  end
+
+  it "keeps the module in the chain when dupping the class" do
+    m = Module.new
+    c = Class.new { prepend(m) }
+    c.dup.new.should be_kind_of(m)
+  end
+
+  it "uses only new module when dupping the module" do
+    m1 = Module.new { def calc(x) x end }
+    m2 = Module.new { prepend(m1) }
+    c1 = Class.new { prepend(m2) }
+    m2dup = m2.dup
+    m2dup.ancestors.should == [m1,m2dup]
+    c2 = Class.new { prepend(m2dup) }
+    c1.ancestors[0,3].should == [m1,m2,c1]
+    c1.new.should be_kind_of(m1)
+    c2.ancestors[0,3].should == [m1,m2dup,c2]
+    c2.new.should be_kind_of(m1)
+  end
+
+  it "depends on prepend_features to add the module" do
+    m = Module.new { def self.prepend_features(mod) end }
+    Class.new { prepend(m) }.ancestors.should_not include(m)
+  end
+
+  it "adds the module in the subclass chains" do
+    parent = Class.new { def chain; [:parent]; end }
+    child = Class.new(parent) { def chain; super << :child; end }
+    mod = Module.new { def chain; super << :mod; end }
+    parent.prepend(mod)
+    parent.ancestors[0,2].should == [mod, parent]
+    child.ancestors[0,3].should == [child, mod, parent]
+
+    parent.new.chain.should == [:parent, :mod]
+    child.new.chain.should == [:parent, :mod, :child]
+  end
+
+  it "inserts a later prepended module into the chain" do
+    m1 = Module.new { def chain; super << :m1; end }
+    m2 = Module.new { def chain; super << :m2; end }
+    c1 = Class.new { def chain; [:c1]; end; prepend m1 }
+    c2 = Class.new(c1) { def chain; super << :c2; end }
+    c2.new.chain.should == [:c1, :m1, :c2]
+    c1.prepend(m2)
+    c2.new.chain.should == [:c1, :m1, :m2, :c2]
+  end
+
+  it "works with subclasses" do
+    m = Module.new do
+      def chain
+        super << :module
+      end
+    end
+
+    c = Class.new do
+      prepend m
+      def chain
+        [:class]
+      end
+    end
+
+    s = Class.new(c) do
+      def chain
+        super << :subclass
+      end
+    end
+
+    s.new.chain.should == [:class, :module, :subclass]
+  end
+
+  it "throws a NoMethodError when there is no more superclass" do
+    m = Module.new do
+      def chain
+        super << :module
+      end
+    end
+
+    c = Class.new do
+      prepend m
+      def chain
+        super << :class
+      end
+    end
+    -> { c.new.chain }.should raise_error(NoMethodError)
+  end
+
+  it "calls prepended after prepend_features" do
+    ScratchPad.record []
+
+    m = Module.new do
+      def self.prepend_features(klass)
+        ScratchPad << [:prepend_features, klass]
+      end
+      def self.prepended(klass)
+        ScratchPad << [:prepended, klass]
+      end
+    end
+
+    c = Class.new { prepend(m) }
+    ScratchPad.recorded.should == [[:prepend_features, c], [:prepended, c]]
+  end
+
+  it "prepends a module if it is included in a super class" do
+    module ModuleSpecs::M3
+      module M; end
+      class A; include M; end
+      class B < A; prepend M; end
+
+      all = [A, B, M]
+
+      (B.ancestors.filter { |a| all.include?(a) }).should == [M, B, A, M]
+    end
+  end
+
+  it "detects cyclic prepends" do
+    -> {
+      module ModuleSpecs::P
+        prepend ModuleSpecs::P
+      end
+    }.should raise_error(ArgumentError)
+  end
+
+  it "doesn't accept no-arguments" do
+    -> {
+      Module.new do
+        prepend
+      end
+    }.should raise_error(ArgumentError)
+  end
+
+  it "returns the class it's included into" do
+    m = Module.new
+    r = nil
+    c = Class.new { r = prepend m }
+    r.should == c
+  end
+
+  it "clears any caches" do
+    module ModuleSpecs::M3
+      module PM1
+        def foo
+          :m1
+        end
+      end
+
+      module PM2
+        def foo
+          :m2
+        end
+      end
+
+      klass = Class.new do
+        prepend PM1
+
+        def get
+          foo
+        end
+      end
+
+      o = klass.new
+      o.get.should == :m1
+
+      klass.class_eval do
+        prepend PM2
+      end
+
+      o.get.should == :m2
+    end
+  end
+
+  it "supports super when the module is prepended into a singleton class" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.inherited(base)
+        super
+      end
+    end
+
+    module_with_singleton_class_prepend = Module.new do
+      singleton_class.prepend(mod)
+    end
+
+    klass = Class.new(ModuleSpecs::RecordIncludedModules) do
+      include module_with_singleton_class_prepend
+    end
+
+    ScratchPad.recorded.should == klass
+  end
+
+  it "supports super when the module is prepended into a singleton class with a class super" do
+    ScratchPad.record []
+
+    base_class = Class.new(ModuleSpecs::RecordIncludedModules) do
+      def self.inherited(base)
+        super
+      end
+    end
+
+    prepended_module = Module.new
+    base_class.singleton_class.prepend(prepended_module)
+
+    child_class = Class.new(base_class)
+    ScratchPad.recorded.should == child_class
+  end
+
+  it "does not interfere with a define_method super in the original class" do
+    base_class = Class.new do
+      def foo(ary)
+        ary << 1
+      end
+    end
+
+    child_class = Class.new(base_class) do
+      define_method :foo do |ary|
+        ary << 2
+        super(ary)
+      end
+    end
+
+    prep_mod = Module.new do
+      def foo(ary)
+        ary << 3
+        super(ary)
+      end
+    end
+
+    child_class.prepend(prep_mod)
+
+    ary = []
+    child_class.new.foo(ary)
+    ary.should == [3, 2, 1]
+  end
+
+  it "does not prepend a second copy if the module already indirectly exists in the hierarchy" do
+    mod = Module.new do; end
+    submod = Module.new do; end
+    klass = Class.new do; end
+    klass.include(mod)
+    mod.prepend(submod)
+    klass.include(mod)
+
+    klass.ancestors.take(4).should == [klass, submod, mod, Object]
+  end
+
+  # https://bugs.ruby-lang.org/issues/17423
+  describe "when module already exists in ancestor chain" do
+    it "modifies the ancestor chain" do
+      m = Module.new do; end
+      a = Module.new do; end
+      b = Class.new do; end
+
+      b.include(a)
+      a.prepend(m)
+      b.ancestors.take(4).should == [b, m, a, Object]
+
+      b.prepend(m)
+      b.ancestors.take(5).should == [m, b, m, a, Object]
+    end
+  end
+
+  describe "called on a module" do
+    describe "included into a class"
+    it "does not obscure the module's methods from reflective access" do
+      mod = Module.new do
+        def foo; end
+      end
+      cls = Class.new do
+        include mod
+      end
+      pre = Module.new
+      mod.prepend pre
+
+      cls.instance_methods.should include(:foo)
+    end
+  end
+end