[WPE-2.38] Missing line/column/sourceURL in Error objects in JS

[piotr-marcinkowski-red]

When inspecting Error objects in webinspector it was found that the following properties were not attached: line, column, sourceURL. In WPE 2.22 these properties are present and in WPE 2.38 they are missing.

During the investigation it was confirmed that:

• line/column are seen in Error instances but they are greyed-out meaning they are not enumerable (for-in loops that go over object's properties just skip them)
• sourceURL is missing at all

These properties are used in one of the test suites which expects them to be attached to Error objects. Since it collects them in a loop over properties it requires these properties to be enumerable.

The following pull request was created that adds the missing properties in Error instances. See the description there for more details on the implementation. https://github.com/LibertyGlobal/WPEWebKit/pull/316

The necessary changes were introduced to JavaScriptCore so it would be justified to first review this modification with great care before deciding to merge it. There is a chance an alternative solution exists which doesn't need changes in such crucial part of code.

[piotr-marcinkowski-red]

[pgorszkowski-igalia]

Making line, column and sourceURL as not enumerable was done in: https://github.com/WebKit/WebKit/commit/330739e633e1fc57394ddfec6b2315b7ca507da9 (Non-standard Error properties should not be enumerable)

[pgorszkowski-igalia]

Probably, changing non-enumerable to enumerable and setting sourceURL from empty to "about:blank" can be done from the JS code, e.g.:

class MyError extends Error {
    constructor(message) {
        super(message); //call superclass constructor

        Object.defineProperty(this, "line", {
        enumerable: true,
        configurable: false,
        writable: true
    });

    if (this.sourceURL === null || this.sourceURL === undefined || (this.sourceURL !== null && this.sourceURL !== undefined && this.sourceURL === ''))
        this.sourceURL = "about:blank";
    }
}

@piotr-marcinkowski-red: Please let me know does it work for you and it is feasible.

[pgorszkowski-igalia]

@piotr-marcinkowski-red: can we close this ticket?

[piotr-marcinkowski-red]

@pgorszkowski-igalia Yes, closing it