Refactor and share logic for Kernel#raise and Thread#raise

* Capture the backtrace directly in Kernel#raise and Thread#raise to
  avoid capturing more backtrace entries to only skip them later.
* Match MRI for the message printed with $DEBUG true for raised exceptions.

Author: eregon

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

@@ -239,14 +239,9 @@ private Object readCustomBacktrace(DynamicObject exception) {
     }
 
     @NonStandard
-    @CoreMethod(names = "capture_backtrace!", optional = 1, lowerFixnum = 1)
+    @CoreMethod(names = "capture_backtrace!", required = 1, lowerFixnum = 1)
     public abstract static class CaptureBacktraceNode extends CoreMethodArrayArgumentsNode {
 
-        @Specialization
-        protected Object captureBacktrace(DynamicObject exception, NotProvided offset) {
-            return captureBacktrace(exception, 1);
-        }
-
         @Specialization
         protected Object captureBacktrace(DynamicObject exception, int offset) {
             final Backtrace backtrace = getContext().getCallStack().getBacktrace(this, offset);

src/main/ruby/truffleruby/core/kernel.rb

@@ -657,8 +657,21 @@ def warn(*messages, uplevel: undefined)
   end
   module_function :warn
 
-  def raise(exc=undefined, msg=undefined, ctx=nil)
-    Truffle::KernelOperations.internal_raise exc, msg, ctx
+  def raise(exc = undefined, msg = undefined, ctx = nil)
+    last = $!
+    if Primitive.undefined?(exc) and last
+      exc = last
+    else
+      exc = Truffle::KernelOperations.build_exception_for_raise(exc, msg)
+
+      exc.set_context ctx if ctx
+      exc.capture_backtrace!(1) unless exc.backtrace?
+      Primitive.exception_set_cause exc, last unless Primitive.object_equal(exc, last)
+    end
+
+    Truffle::KernelOperations.show_exception_for_debug(exc, 1) if $DEBUG
+
+    Primitive.vm_raise_exception exc
   end
   module_function :raise
 

src/main/ruby/truffleruby/core/thread.rb

@@ -282,30 +282,15 @@ def inspect
   end
   alias_method :to_s, :inspect
 
-  def raise(exc=undefined, msg=undefined, ctx=nil)
+  def raise(exc = undefined, msg = undefined, ctx = nil)
     return nil unless alive?
 
-    if Primitive.undefined? exc
-      exc = RuntimeError.exception ''
-    elsif exc.respond_to? :exception
-      if Primitive.undefined? msg
-        exc = exc.exception
-      else
-        exc = exc.exception msg
-      end
-      Kernel.raise TypeError, 'exception class/object expected' unless Exception === exc
-    elsif exc.kind_of? String
-      exc = RuntimeError.exception exc
-    else
-      Kernel.raise TypeError, 'exception class/object expected'
-    end
+    exc = Truffle::KernelOperations.build_exception_for_raise(exc, msg)
 
     exc.set_context ctx if ctx
     exc.capture_backtrace!(1) unless exc.backtrace?
 
-    if $DEBUG
-      STDERR.puts "Exception: `#{exc.class}' - #{exc.message}"
-    end
+    Truffle::KernelOperations.show_exception_for_debug(exc, 1) if $DEBUG
 
     if self == Thread.current
       Primitive.vm_raise_exception exc

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

@@ -128,41 +128,39 @@ def self.load_error(name)
       load_error
     end
 
-    def self.internal_raise(exc, msg, ctx)
-      skip = false
+    def self.build_exception_for_raise(exc, msg)
       if Primitive.undefined? exc
-        exc = $!
-        if exc
-          skip = true
-        else
-          exc = RuntimeError.new ''
-        end
+        ::RuntimeError.exception ''
       elsif exc.respond_to? :exception
         if Primitive.undefined? msg
           exc = exc.exception
         else
           exc = exc.exception msg
         end
-        raise TypeError, 'exception class/object expected' unless exc.kind_of?(Exception)
-      elsif exc.kind_of? String
-        exc = RuntimeError.exception exc
+
+        exception_class_object_expected! unless Primitive.object_kind_of?(exc, ::Exception)
+        exc
+      elsif exc.kind_of? ::String
+        ::RuntimeError.exception exc
       else
-        raise TypeError, 'exception class/object expected'
+        exception_class_object_expected!
       end
+    end
 
-      unless skip
-        exc.set_context ctx if ctx
-        exc.capture_backtrace!(2) unless exc.backtrace?
-        Primitive.exception_set_cause exc, $! unless exc.equal?($!)
-      end
+    # Avoid using #raise here to prevent infinite recursion
+    def self.exception_class_object_expected!
+      exc = ::TypeError.new('exception class/object expected')
+      exc.capture_backtrace!(1)
 
-      if $DEBUG
-        STDERR.puts "Exception: `#{exc.class}' #{caller(2, 1)[0]} - #{exc.message}\n"
-      end
+      Truffle::KernelOperations.show_exception_for_debug(exc, 2) if $DEBUG
 
       Primitive.vm_raise_exception exc
     end
 
+    def self.show_exception_for_debug(exc, uplevel)
+      STDERR.puts "Exception: `#{exc.class}' at #{caller(uplevel + 1, 1)[0]} - #{exc.message}\n"
+    end
+
     def self.check_last_line(line)
       unless Primitive.object_kind_of? line, String
         raise TypeError, "$_ value need to be String (#{Truffle::ExceptionOperations.to_class_name(line)} given)"