[tor-bugs] #12087 [Pluggable transport]: goptlib could provide IsClient()/IsServer().

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#12087: goptlib could provide IsClient()/IsServer().
-------------------------------------+------------------------------
     Reporter:  yawning              |      Owner:  asn
         Type:  enhancement          |     Status:  needs_review
     Priority:  minor                |  Milestone:
    Component:  Pluggable transport  |    Version:
   Resolution:                       |   Keywords:  goptlib, library
Actual Points:                       |  Parent ID:
       Points:                       |
-------------------------------------+------------------------------

Comment (by dcf):

 Replying to [comment:1 dcf]:
 > Proposed patch:
 >  * https://gitweb.torproject.org/pluggable-
 transports/goptlib.git/commitdiff/c1482145a738b9378ee6a5f7067544bea7414f34

 I'm fine with applications having to peek at environment variables if they
 need this functionality, at least in the short term.

 I'm thinking about the application's interface to these functions. I guess
 it would have to look like this?
 {{{
 if pt.IsClient() {
         // do client stuff
 } else if pt.IsServer() {
         // do server stuff
 } else {
         // handle error? pt.EnvError?
 }
 }}}
 Since "client mode" and "server mode" are the only two possibilities,
 maybe it makes sense to have only one function to test the mode, rather
 than two, so that there can be no ambiguity or disagreement between the
 two functions? In other words,
 {{{
 if pt.IsClient() {
         // do client stuff
 } else {
         // do server stuff
 }
 }}}
 If there are two separate functions, then we should document and implement
 one to be the inverse of the other, rather than having two separate
 functions testing two different environment variables. I'm not such a fan
 of that idea, because the second function amounts to a convenience
 function. It would look like:
 {{{
 func IsServer() bool {
         return !IsClient()
 }
 }}}

 I'd like there to be additional test cases. The code should do something
 reasonable in all of them.
  1. TOR_PT_CLIENT_TRANSPORTS and TOR_PT_SERVER_TRANSPORTS both unset.
  2. TOR_PT_CLIENT_TRANSPORTS unset, TOR_PT_SERVER_TRANSPORTS set.
  3. TOR_PT_CLIENT_TRANSPORTS set, TOR_PT_SERVER_TRANSPORTS unset.
  4. TOR_PT_CLIENT_TRANSPORTS and TOR_PT_SERVER_TRANSPORTS both set.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12087#comment:2>
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