On Fri, Feb 2, 2018 at 9:47 AM, Boris Zbarsky <bzbar...@mit.edu> wrote:
> > What happens if a user's prefs file has things that were OK but now fail? > Is it effectively dataloss in that we will not parse anything after that > and then write out the modified pref file with all the later things missing? > There are two kinds of "user's prefs". - prefs.js, which is written by Firefox. Firefox should always generate data that is accepted by the new parser, so I don't think there is a problem there. (If users do hand-edit, there might be problems. But that file has a big "Do not edit this file" warning at the top, so I'm not too worried about that case.) - user.js, which is hand-written by users. If there is a syntax error in this file the parser will issue an error message[*], abort, and any prefs after the syntax error will be ignored, but Firefox will otherwise run normally. So I don't think data loss is a concern, but user.js prefs that were previously accepted might now be ignored. [*] One tricky question is what to do with syntax errors. The current behaviour is here: https://searchfox.org/mozilla-central/source/modules/libpref/Preferences.cpp#1000-1011. It writes the error to the browser console, but if that fails, prints it to stderr instead. And then it also does an NS_WARNING. This means that errors are easy to overlook, especially in user.js. Do you have suggestions on a better approach? Do you think the parser should do error recovery? Bug 107624 has some context for this. - The old parser allowed integer literals to overflow, silently wrapping >> them. >> >> The new parser treats integer overflow as a parse error. >> > > This seems like a footgun for users who set numeric prefs by hand... > Silently wrapping was also a footgun that came up in practice in bug 1424030 and bug 1434813. IMO it's better to give a clear error than to silently do the wrong thing... Nick _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
