181654 - Calling toString for an object derived from the Error class throws TypeError

Status: VERIFIED FIXED

(Rhino Graveyard :: Core, defect)

Description

[Jörg Schaible]

User-Agent:       Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; Q312461)
Build Identifier: Rhino 1.5 release 4 0000 00 00 (in progress)

Calling the toString method for an object that is derived from the Error class 
results in a thrown TypeError (Rhino only, works perfectly in SpiderMonkey).

Reproducible: Always

Steps to Reproduce:
regression test case attached
Actual Results:  
TypeError raised

Expected Results:  
same behaviour as with SpiderMonkey: method returns String with class name and 
error message.

Environment is reproducable with Rhino 1.5 RC4pre from current CVS

Comment 1

[Jörg Schaible]

Attachment: js\tests\ecma_3\Exceptions\regress-181654.js

Regression test for this bug.

Comment 2

[Phil Schwartau]

Jörg's testcase added to JS testsuite:

      mozilla/js/tests/ecma_3/Exceptions/regress-181654.js

Comment 3

[Phil Schwartau]

Confirming what Jörg has reported. SpiderMonkey passes the above test,
whereas Rhino generates a TypeError. Here is an example:


---------------------------  IN SPIDERMONKEY  ---------------------------
js> function f() {}
js> f.prototype = new Error();
Error
js> obj = new f();
Error
js> obj.toString();
Error


---------------------------  IN RHINO  ---------------------------
js> function f() {}
js> f.prototype = new Error();
Error: undefined
js> obj = new f();
js: "<stdin>", line 25: uncaught JavaScript exception: TypeError:
Method "toString" called on incompatible object. (<stdin>; line 25)
js> obj.toString();
js: "<stdin>", line 26: uncaught JavaScript exception: TypeError:
Method "toString" called on incompatible object. (<stdin>; line 26)


Note, no trouble in Rhino for a primary Error object:

js> obj = new Error();
Error: undefined
js> obj.toString();
Error: undefined

Comment 4

[Igor Bukanov]

Attachment: Making Error.prototype.toString generic

I guess it is possible to argue that current Rhino behavior confirms Ecma 262,
v3 as according to 15.11.4.4  Error.prototype.toString() returns an
implementation defined string, and throwing an exception can be very well
defined result ;).

But as not throwing exceptions fulfills 15.11.4.4 without guesses, here is a
patch that effectively makes Error.prototype.toString a generic function
printing this.name + ": " + this.message for any this.

Comment 5

[Igor Bukanov]

Can be marked as fixed as I commited the attachment

Comment 6

[Phil Schwartau]

Marking FIXED -

Comment 7

[Phil Schwartau]

Marking Verified FIXED.

The above testcase now passes in the Rhino shell, in both compiled
and interpreted modes. Here is an interactive session:

[ ] java org.mozilla.javascript.tools.shell.Main
Rhino 1.5 release 4 0000 00 00 (in progress)

js> function f() {}
js> f.prototype = new Error();
Error:
js> obj = new f();
Error:
js> obj.toString()
Error:

js> f.prototype = new SyntaxError();
SyntaxError:
js> obj = new f();
SyntaxError:
js> obj.toString()
SyntaxError:

js> f.prototype = new TypeError();
TypeError:
js> obj = new f();
TypeError:
js> obj.toString()
TypeError:

Comment 8

[Igor Bukanov]

Targeting as resolved against 1.5R4