not overwrite cause

* eval.c (setup_exception): set the cause only if it is explicitly
  given or not set yet.  [Bug #12068]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53819 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 72 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 7b7340fbb8..64fea3dd57 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Feb 14 16:18:57 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* eval.c (setup_exception): set the cause only if it is explicitly
+	  given or not set yet.  [Bug #12068]
+
 Sat Feb 13 21:44:58 2016  Tanaka Akira  <akr@fsij.org>
 
 	* hash.c (rb_hash_invert): [DOC] more examples.
diff --git a/eval.c b/eval.c
index b9fcd86f5c..91fb2c9e9f 100644
--- a/eval.c
+++ b/eval.c
@@ -25,6 +25,7 @@ VALUE rb_eLocalJumpError;
 VALUE rb_eSysStackError;
 
 ID ruby_static_id_signo, ruby_static_id_status;
+static ID id_cause;
 #define id_signo ruby_static_id_signo
 #define id_status ruby_static_id_status
 
@@ -442,9 +443,6 @@ static VALUE get_thread_errinfo(rb_thread_t *th);
 static VALUE
 exc_setup_cause(VALUE exc, VALUE cause)
 {
-    ID id_cause;
-    CONST_ID(id_cause, "cause");
-
 #if SUPPORT_JOKE
     if (NIL_P(cause)) {
 	ID id_true_cause;
@@ -488,10 +486,15 @@ setup_exception(rb_thread_t *th, int tag, volatile VALUE mesg, VALUE cause)
 	mesg = rb_exc_new(rb_eRuntimeError, 0, 0);
 	nocause = 0;
     }
-    if (cause == Qundef) {
-	cause = nocause ? Qnil : get_thread_errinfo(th);
+    if (cause != Qundef) {
+	exc_setup_cause(mesg, cause);
+    }
+    else if (nocause) {
+	exc_setup_cause(mesg, Qnil);
+    }
+    else if (!rb_ivar_defined(mesg, id_cause)) {
+	exc_setup_cause(mesg, get_thread_errinfo(th));
     }
-    exc_setup_cause(mesg, cause);
 
     file = rb_source_loc(&line);
     if (file && !NIL_P(mesg)) {
@@ -1668,4 +1671,5 @@ Init_eval(void)
 
     id_signo = rb_intern_const("signo");
     id_status = rb_intern_const("status");
+    id_cause = rb_intern_const("cause");
 }
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index 8435c5a5ee..6a1e4864f0 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -625,6 +625,44 @@ end.join
     assert_not_same(e, e.cause, "#{msg}: should not be recursive")
   end
 
+  def test_cause_raised_in_rescue
+    e = assert_raise_with_message(RuntimeError, 'b') {
+      begin
+        raise 'a'
+      rescue => a
+        begin
+          raise 'b'
+        rescue => b
+          begin
+            raise 'c'
+          rescue
+            raise b
+          end
+        end
+      end
+    }
+    assert_equal('a', e.cause.message, 'cause should not be overwritten by reraise')
+  end
+
+  def test_cause_at_raised
+    e = assert_raise_with_message(RuntimeError, 'b') {
+      begin
+        raise 'a'
+      rescue => a
+        b = RuntimeError.new('b')
+        begin
+          raise 'c'
+        rescue
+          raise b
+        end
+      end
+    }
+    assert_equal('c', e.cause.message, 'cause should be the exception at raised')
+  end
+
+  def test_cause_at_raised
+  end
+
   def test_raise_with_cause
     msg = "[Feature #8257]"
     cause = ArgumentError.new("foobar")
@@ -639,6 +677,25 @@ end.join
     end
   end
 
+  def test_raise_with_cause_in_rescue
+    e = assert_raise_with_message(RuntimeError, 'b') {
+      begin
+        raise 'a'
+      rescue => a
+        begin
+          raise 'b'
+        rescue => b
+          begin
+            raise 'c'
+          rescue
+            raise b, cause: ArgumentError.new('d')
+          end
+        end
+      end
+    }
+    assert_equal('d', e.cause.message, 'cause option should be honored always')
+  end
+
   def test_unknown_option
     bug = '[ruby-core:63203] [Feature #8257] should pass unknown options'