Feature-detect "use regular streams as an underlying socket for tls.connect()"

[dougwilson]

Hi, I'm looking for a good solution to be able to detect if this feature exists in the runtime my module is running on so I can throw if it's not supported. It was suggested on IRC to make an issue here.

I originally thought perhaps if I just construct a duplex stream and pass it into tls.connect, but it doesn't seem to throw an error on pre-1.4.1 versions. Suggestions?

// This doesn't seem to work
var supportswrappedjsstreams = (function(){
 var s = require("stream").Duplex();s._read=s._write=function(){};
 try { require("tls").connect({ stream: s }); return true; } catch { return false; }
});

// This does work, but not sure if this is going to suddenly break in the future
var supportswrappedjsstreams = (function(){
 try { require("_stream_wrap"); return true; } catch { return false; }
});

[tellnes]

@indutny

[chrisdickinson]

Not sure about the state it leaves the SSL context in, but something like:

var supportswrappedjsstreams = (function(){
 var s = require("stream").Duplex(); s._read = s._write = Function();
 require('tls').connect({socket: s});
 return require('events').listenerCount('error', s) > 0;
});

should work since TLS/streamwrap will always have to install error handlers.

[dougwilson]

Ah, yes, that does seem to work, even to weed out Node.js stuff. Thanks!

[dougwilson]

Oops, I may have closed that too early, because I only tested the pre-1.4.1 versions; it actually seems to have 0 listeners, even on 1.4.1:

$ iojs -pe 's=require("stream").Duplex();s._read=s._write=function(){};require("tls").connect({socket:s});require("events").EventEmitter.listenerCount("error",s)'
0

$ iojs -v
v1.4.1

[chrisdickinson]

Ah, whoops: it should be EE.listenerCount(emitter, "eventName");. My bad!

[indutny]

Interesting question! Why not just check the process.version? :)

[mathiasbynens]

Checking process.version is to user-agent sniffing as feature testing is to, uhm, feature testing. Inferring behavior from a version number seems brittle IMHO.

[indutny]

@mathiasbynens the proposed check is much more brittle than version checking. We have semver, so this thing can't go away until 2.0.0 for sure.

[chrisdickinson]

@dougwilson I think the check works now – ok to close?

[dougwilson]

The only working check that was provided here was to sniff the version and at the same time, I'm told in this thread not to sniff the version. I need clarification still: should I start version sniffing io.js features or can someone come up with a non-version-sniffing solution to this?

[chrisdickinson]

@dougwilson Did you see my message about the order of EE.listenerCount params?