Run END keyword block only once at exit

Author: bjfish

CHANGELOG.md

@@ -45,6 +45,7 @@ Bug fixes:
 * Make `Enumerable#chunk` work without a block (#1518).
 * Fixed issue with `SystemCallError.new` setting a backtrace.
 * Fixed `BigDecimal#to_s` formatting issue (#1711).
+* Run `END` keyword block only once at exit.
 
 Compatibility:
 

spec/ruby/language/END_spec.rb

@@ -0,0 +1,15 @@
+require_relative '../spec_helper'
+
+describe "The END keyword" do
+  it "runs only once for multiple calls" do
+    ruby_exe("10.times { END { puts 'foo' }; } ").should == "foo\n"
+  end
+
+  it "runs last in a given code unit" do
+    ruby_exe("END { puts 'bar' }; puts'foo'; ").should == "foo\nbar\n"
+  end
+
+  it "runs multiple ends in LIFO order" do
+    ruby_exe("END { puts 'foo' }; END { puts 'bar' }").should == "bar\nfoo\n"
+  end
+end

spec/tags/language/END_tags.txt

@@ -0,0 +1,3 @@
+slow:The END keyword runs only once for multiple calls
+slow:The END keyword runs last in a given code unit
+slow:The END keyword runs multiple ends in LIFO order

src/main/java/org/truffleruby/parser/BodyTranslator.java

@@ -2694,18 +2694,20 @@ public RubyNode visitPostExeNode(PostExeParseNode node) {
 
         final SourceIndexLength position = node.getPosition();
 
-        return translateCallNode(
-                new CallParseNode(
-                        position,
-                        new TruffleFragmentParseNode(
+        return new OnceNode(
+                translateCallNode(
+                        new CallParseNode(
                                 position,
-                                new ObjectLiteralNode(context.getCoreLibrary().getTruffleKernelOperationsModule())),
-                        "at_exit",
-                        new ArrayParseNode(position, new TrueParseNode(position)),
-                        new IterParseNode(position, node.getArgsNode(), scope, node.getBodyNode())),
-                false,
-                false,
-                false);
+                                new TruffleFragmentParseNode(
+                                        position,
+                                        new ObjectLiteralNode(
+                                                context.getCoreLibrary().getTruffleKernelOperationsModule())),
+                                "at_exit",
+                                new ArrayParseNode(position, new TrueParseNode(position)),
+                                new IterParseNode(position, node.getArgsNode(), scope, node.getBodyNode())),
+                        false,
+                        false,
+                        false));
     }
 
     @Override