Fix issue with takeUntil in nested stream

This issue was caused by #180 which made sure that nested streams were
updated properly. Updating them properly caused nested takeUntil'd
streams to end too soon.

module/switchlatest/index.js

@@ -1,12 +1,10 @@
 var flyd = require('../../lib');
 var takeUntil = require('../takeuntil');
-var drop = require('ramda/src/drop');
 
-var dropCurrentValue = flyd.transduce(drop(1));
 
 module.exports = function(s) {
   return flyd.combine(function(stream$, self) {
     var value$ = stream$();
-    flyd.on(self, takeUntil(value$, dropCurrentValue(stream$)));
+    flyd.on(self, takeUntil(value$, stream$));
   }, [s]);
 };

module/takeuntil/index.js

@@ -1,7 +1,11 @@
 var flyd = require('../../lib');
+var drop = require('ramda/src/drop');
+
+var dropCurrentValue = flyd.transduce(drop(1));
 
 module.exports = flyd.curryN(2, function(src, term) {
-  return flyd.endsOn(flyd.merge(term, src.end), flyd.combine(function(src, self) {
+  var end$ = term.hasVal ? dropCurrentValue(term) : term;
+  return flyd.endsOn(flyd.merge(end$, src.end), flyd.combine(function(src, self) {
     self(src());
   }, [src]));
 });

module/takeuntil/test/index.js

@@ -38,4 +38,24 @@ describe('takeUntil', function() {
     assert.deepEqual(result, [1]);
     assert(s.end());
   });
+
+  it('works in nested streams', function() {
+    var source = stream(1);
+    var terminator = stream(true);
+
+    var value = stream(1).chain(function() {
+      return takeUntil(source, terminator);
+    })
+      .map(function(val) {
+        return val + 1;
+      });
+
+    source(2)(3)(4)(5);
+
+    terminator(true);
+
+    source(6)(7)(8)(9);
+
+    assert.equal(value(), 6);
+  })
 });