Bug 187724 – JSON.stringify should emit non own properties if second array argument includes

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[zac spitzer]

The following test case produces an empty object in Webkit

https://jsbin.com/qiluqen/edit?js,console

Firefox, Edge and Chrome all output an object with three properties

function createSyntaxException() {
    try {
        // trigger a DOMException
        document.querySelectorAll("div:foo");
    } catch(e) {
        // this produces an empty object in webkit
        var err = JSON.parse(
          JSON.stringify(e, ['code','name','message'] )
        );      
        console.log(err);
        console.log(JSON.stringify(err));        
        var err2 = {
          code: e.code,
          name: e.name,
          message: e.message
        };
        console.log(err2);
    }
}
throw createSyntaxException();

[Radar WebKit Bug Importer]

<rdar://problem/42310909>

[Yusuke Suzuki]

It seems that WebKit behavior is correct, but I would like to hear opinions from binding folks. My understanding is the following.

According to DOMException's IDL, defined in WebIDL.

https://heycam.github.io/webidl/#idl-DOMException

interface DOMException { // but see below note about ECMAScript binding
  readonly attribute DOMString name;
  readonly attribute DOMString message;
  readonly attribute unsigned short code;

  const unsigned short INDEX_SIZE_ERR = 1;
...

This definition says that "name", "message", and "code" are readonly attributes. So they should be defined as getters in DOMException.prototype.

From the point of view of JSC, this makes `JSON.stringify(error)` empty since "name", "message", and "code" are not own properties.

[zac spitzer]

but I'm passing in an array of ['code','name','message'] as a replacer to stringify which should pluck those values out?

[Yusuke Suzuki]

Ah, I missed the point. The second argument array forces us to emit properties even if it is not an own property.

[Yusuke Suzuki]

Created attachment 345235 [details]
Patch

[EWS Watchlist]

Comment on attachment 345235 [details]
Patch

Attachment 345235 [details] did not pass win-ews (win):
Output: https://webkit-queues.webkit.org/results/8573642

New failing tests:
http/tests/security/local-video-source-from-remote.html

[EWS Watchlist]

Created attachment 345237 [details]
Archive of layout-test-results from ews206 for win-future

The attached test failures were seen while running run-webkit-tests on the win-ews.
Bot: ews206  Port: win-future  Platform: CYGWIN_NT-6.1-2.9.0-0.318-5-3-x86_64-64bit

[Mark Lam]

Comment on attachment 345235 [details]
Patch

r=me

[Yusuke Suzuki]

Comment on attachment 345235 [details]
Patch

Thank you!

[WebKit Commit Bot]

Comment on attachment 345235 [details]
Patch

Clearing flags on attachment: 345235

Committed r233924: <https://trac.webkit.org/changeset/233924>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.