[ruby/ostruct] Emit a performance warning when OpenStruct is used

(https://github.com/ruby/ostruct/pull/56)

The OpenStruct documentation clearly state that it shouldn't
be used when performance is expected.

Ruby 3.3 introduce a new category of warnings that is silenced
by default: performance.

The expected use case is to enable this warning when looking
for potential performance issues within an application.

As such I think it would make sense to emit a performance warning
when OpenStruct is used, as it may help pinpoint that a dependency
rely on it, etc.

https://github.com/ruby/ostruct/commit/5826e12db8

Co-authored-by: Jean Boussier <[email protected]>

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/ostruct.rb b/lib/ostruct.rb
index a08561d6c9..7311138fbf 100644
--- a/lib/ostruct.rb
+++ b/lib/ostruct.rb
@@ -109,6 +109,14 @@
 class OpenStruct
   VERSION = "0.5.5"
 
+  HAS_PERFORMANCE_WARNINGS = begin
+    Warning[:performance]
+    true
+  rescue NoMethodError, ArgumentError
+    false
+  end
+  private_constant :HAS_PERFORMANCE_WARNINGS
+
   #
   # Creates a new OpenStruct object.  By default, the resulting OpenStruct
   # object will have no attributes.
@@ -124,6 +132,10 @@ class OpenStruct
   #   data   # => #<OpenStruct country="Australia", capital="Canberra">
   #
   def initialize(hash=nil)
+    if HAS_PERFORMANCE_WARNINGS && Warning[:performance]
+       warn "OpenStruct use is discouraged for performance reasons", uplevel: 1, category: :performance
+    end
+
     if hash
       update_to_values!(hash)
     else