Bug 160984 – Make custom Error properties (line, column, sourceURL) configurable and writable

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Joseph Pecoraro]

Summary:
Custom Error properties (line, column, sourceURL) should be writable and configurable

Steps to Reproduce:
>>> "use strict"; (new SyntaxError).line = 1;
Exception: TypeError: Attempted to assign to readonly property.

--

Some JavaScript libraries (Objective-J) expect to be able to assign to the "line" and "column" properties of a SyntaxError instance they create. This currently doesn't work in Safari where these properties are readonly.

>    function raise(pos, message) {
>      if (typeof pos == "number") pos = getLineInfo(input, pos);
>      var syntaxError = new SyntaxError(message);
>      syntaxError.line = pos.line;
>      syntaxError.column = pos.column;
>      syntaxError.lineStart = pos.lineStart;
>      syntaxError.lineEnd = pos.lineEnd;
>      syntaxError.fileName = sourceFile;
>
>      throw syntaxError;
>    }


In strict mode, this throws an exception, which was unexpected. We should be more lenient.

Notes:
- These properties are non-standard. Firefox adds (lineNumber, columnNumber, fileName). I didn't see any in Chrome.
- Non-standard Error properties added by JavaScriptCore are currently readonly and enumerable.
- All other engine non-standard error properties are configurable, writable, and not enumerable.
- Lets start by making them configurable/writable.

[Joseph Pecoraro]

<rdar://problem/27905979>

[Joseph Pecoraro]

Created attachment 286418 [details]
[PATCH] Proposed Fix

[WebKit Commit Bot]

Comment on attachment 286418 [details]
[PATCH] Proposed Fix

Clearing flags on attachment: 286418

Committed r204663: <http://trac.webkit.org/changeset/204663>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Joseph Pecoraro]

*** Bug 146047 has been marked as a duplicate of this bug. ***