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POFind and report Javascript compilation errors in XULRunner using nsIScriptContext or the SpiderMonkey API
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copied!<p>I have an experimental version of wxWebConnect (embedding XULRunner in wxWidgets) at <a href="https://github.com/jonmmorgan/wxwebconnect/" rel="nofollow">https://github.com/jonmmorgan/wxwebconnect/</a>. It offers a method</p> <pre><code>wxString wxWebControl::ExecuteScriptWithResult(const wxString& js_code) </code></pre> <p>which executes the Javascript string using nsIScriptContext::EvaluateStringWithValue, converts the value to a string with JS_ValueToString, and then returns the string.</p> <p>However, I found with the current implementation that if the Javascript string is syntactically invalid (e.g. WebControl.ExecuteScriptWithResult('{a:2')) then the program would crash when trying to convert the result to a string. I discovered the aIsUndefined parameter, which I can use to determine whether script execution succeeded or not and prevent the crash. However, this doesn't help me find what the actual error was, and I think it would be good to report that (like Firebug tells me "SyntaxError: missing } in compound statement"). As far as I can see, even using something like nsIScriptContext::CompileScript will just tell me whether the compilation succeeded or not, and doesn't give me a way to get at the actual syntax error.</p> <p>Following <a href="http://chadaustin.me/2009/02/evaluating-javascript-in-an-embedded-xulrunnergecko-window/" rel="nofollow">http://chadaustin.me/2009/02/evaluating-javascript-in-an-embedded-xulrunnergecko-window/</a>, I tried using JS_GetPendingException, but it never seems to return true. Even when I run webcontrol.ExecuteScriptWithResult("throw new Error('a');") it still doesn't have a pending exception, but does say the result is undefined.</p> <p>Is there any other good way to get a compilation or execution error from nsIScriptContext or the SpiderMonkey API? Any idea why JS_GetPendingException doesn't seem to do this?</p>

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