Do we need platform sniffing if we have feature detection?

[seaneagan]

AFAIK feature detection is generally preferable to platform sniffing ("user agent sniffing" in the web world). So why do we need the latter?

[seaneagan]

For example, maybe chrome apps will get full access to dart:io in the future. Presumably chrome apps would be a separate platform. It would better to check dart.feature.io == 'true' than dart.platform == 'server'.

[seaneagan]

@mezoni For reference, I'm referring to these chrome apps. They have access to for example a JavaScript file system API. One can write a dart API which proxies to that JavaScript API like chrome.dart. If they want to have a direct dart API instead, maybe they'll just embed a version of dart:io which fails at runtime for some things that it can't support, instead of exposing custom chrome app dart APIs. Could be a bad example, but was just trying to make the point that dart.feature.* and dart.platform may be duplicative, and that features may be preferred since a feature may be available on multiple platforms.

[zoechi]

I think for tools like the analyzer it would be much more difficult. A platform is just the whole set of features. Small differences (differences between Firefox, Safari, Chrome) wouldn't be considered anyway and woulnd't make much sense except dart2js switches to an output format like GWT does with a build output per browser version.

[BillDStrong]

@zoechi
Agreed, as a user, I would only want to care about being deployed to server, web or packaged app. Maybe packaged app would be split into mobile or desktop, if there is ever a story there.

[lrhn]

I'd sat no, we don't need platform selection if we have feature selection.
The platform selection was the initial request, so it's still in there.