[GR-18163] Fix "circular causes" error at re-raising exception when it's caused by implicitly raised exception

PullRequest: truffleruby/4553

Author: andrykonchin

spec/ruby/core/kernel/raise_spec.rb

@@ -240,6 +240,25 @@
     end
   end
 
+  it "re-raises a previously rescued exception that doesn't have a cause and is a cause of other exception (that wasn't raised explicitly) without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          foo # raises NameError
+        rescue => e2
+          e1.cause.should == nil
+          e2.cause.should == e1
+          raise e1
+        end
+      end
+    rescue => e
+      e.should == e1
+      e.cause.should == nil
+    end
+  end
+
   it "re-raises a previously rescued exception that has a cause but isn't a cause of any other exception without setting a cause implicitly" do
     begin
       begin

src/main/java/org/truffleruby/core/exception/RubyException.java

@@ -50,6 +50,8 @@ public class RubyException extends RubyDynamicObject implements ObjectGraphNode
     public Object backtraceLocations = null;
     /** null (not set), RubyArray of Strings, or nil (empty) */
     public Object customBacktrace = null;
+    /** whether a Ruby exception referencing this exception as its cause exists. One of the way to prevent circles in
+     * exception cause chains */
     public boolean usedAsACause = false;
 
     public RubyException(RubyClass rubyClass, Shape shape, Object message, Backtrace backtrace, Object cause) {
@@ -58,6 +60,10 @@ public RubyException(RubyClass rubyClass, Shape shape, Object message, Backtrace
         this.message = message;
         this.backtrace = backtrace;
         this.cause = cause;
+
+        if (cause instanceof RubyException) {
+            ((RubyException) cause).usedAsACause = true;
+        }
     }
 
     @TruffleBoundary