Re-raising an exception no longer sets the cause.

Author: aardvark179

CHANGELOG.md

@@ -5,6 +5,7 @@ Bug fixes:
 * Fixed `BigDecimal#dup` so it now just returns the receiver, per Ruby 2.5+ semantics (#1680).
 * Implemented `rb_eval_string_protect`.
 * Fixed `rb_get_kwargs` to correctly handle optional and rest arguments.
+* Calling `Kernel#raise` with a raised exception will no longer set the cause of the exception to itself (#1682).
 
 # 1.0 RC 17
 

spec/ruby/core/exception/cause_spec.rb

@@ -41,4 +41,16 @@
       e.cause.should equal(cause)
     }
   end
+
+  it "is not set to the exception itself when it is re-raised" do
+    -> {
+      begin
+        raise RuntimeError
+      rescue RuntimeError => e
+        raise e
+      end
+    }.should raise_error(RuntimeError) { |e|
+      e.cause.should == nil
+    }
+  end
 end

src/main/ruby/core/truffle/kernel_operations.rb

@@ -141,7 +141,7 @@ def self.internal_raise(exc, msg, ctx, internal)
       unless skip
         exc.set_context ctx if ctx
         exc.capture_backtrace!(2) unless exc.backtrace?
-        Truffle.invoke_primitive :exception_set_cause, exc, $!
+        Truffle.invoke_primitive :exception_set_cause, exc, $! unless exc.equal?($!)
       end
 
       if $DEBUG