ObjectSpace.dump_all: dump shapes as well

I see several arguments in doing so.

First they use a non trivial amount of memory, so for various memory
profiling/mapping tools it is relevant to have visibility of the space
occupied by shapes.

Then, some pathological code can create a tons of shape, so it is
valuable to have a way to have a way to observe shapes without having
to compile Ruby with `SHAPE_DEBUG=1`.

And additionally it's likely much faster to dump then this way than
to use `RubyVM::Shape`.

There are however a few open questions:

- Shapes can't respect the `since:` argument. Not sure what to do when
  it is provided. Would probably make sense to not dump them.
- Maybe it would make more sense to have a separate `ObjectSpace.dump_shapes`?
- Maybe instead `dump_all` should take a `shapes: false` argument?

Additionally, `ObjectSpace.dump_shapes` is added for the use case of
debugging the evolution of the shape tree.

1 files changed, 13 insertions, 2 deletions

diff --git a/test/objspace/test_objspace.rb b/test/objspace/test_objspace.rb
index 1eded6a439..7eda077260 100644
--- a/test/objspace/test_objspace.rb
+++ b/test/objspace/test_objspace.rb
@@ -414,7 +414,7 @@ class TestObjSpace < Test::Unit::TestCase
           @obj1 = Object.new
           GC.start
           @obj2 = Object.new
-          ObjectSpace.dump_all(output: :stdout, since: gc_gen)
+          ObjectSpace.dump_all(output: :stdout, since: gc_gen, shapes: false)
         end
 
         p dump_my_heap_please
@@ -422,7 +422,7 @@ class TestObjSpace < Test::Unit::TestCase
       assert_equal 'nil', output.pop
       since = output.shift.to_i
       assert_operator output.size, :>, 0
-      generations = output.map { |l| JSON.parse(l)["generation"] }.uniq.sort
+      generations = output.map { |l| JSON.parse(l) }.map { |o| o["generation"] }.uniq.sort
       assert_equal [since, since + 1], generations
     end
   end
@@ -479,6 +479,7 @@ class TestObjSpace < Test::Unit::TestCase
       output.each { |l|
         obj = JSON.parse(l)
         next if obj["type"] == "ROOT"
+        next if obj["type"] == "SHAPE"
 
         assert_not_nil obj["slot_size"]
         assert_equal 0, obj["slot_size"] % GC::INTERNAL_CONSTANTS[:RVALUE_SIZE]
@@ -794,6 +795,16 @@ class TestObjSpace < Test::Unit::TestCase
     assert_equal name, JSON.parse(dump)["method"], dump
   end
 
+  def test_dump_shapes
+    json = ObjectSpace.dump_shapes(output: :string)
+    json.each_line do |line|
+      assert_include(line, '"type":"SHAPE"')
+    end
+
+    assert_empty ObjectSpace.dump_shapes(output: :string, since: RubyVM.stat(:next_shape_id))
+    assert_equal 2, ObjectSpace.dump_shapes(output: :string, since: RubyVM.stat(:next_shape_id) - 2).lines.size
+  end
+
   private
 
   def utf8_❨╯°□°❩╯︵┻━┻