Fix combineLatest to produce the subscription.

rx.lua

@@ -488,6 +488,7 @@ function Observable:combineLatest(...)
     local latest = {}
     local pending = {util.unpack(sources)}
     local completed = {}
+    local subscription = {}
 
     local function onNext(i)
       return function(value)
@@ -517,8 +518,14 @@ function Observable:combineLatest(...)
     end
 
     for i = 1, #sources do
-      sources[i]:subscribe(onNext(i), onError, onCompleted(i))
+      subscription[i] = sources[i]:subscribe(onNext(i), onError, onCompleted(i))
     end
+
+    return Subscription.create(function ()
+      for i = 1, #subscription do
+        if subscription[i] then subscription[i]:unsubscribe() end
+      end
+    end)
   end)
 end
 

src/operators/combineLatest.lua

@@ -21,6 +21,7 @@ function Observable:combineLatest(...)
     local latest = {}
     local pending = {util.unpack(sources)}
     local completed = {}
+    local subscription = {}
 
     local function onNext(i)
       return function(value)
@@ -50,7 +51,13 @@ function Observable:combineLatest(...)
     end
 
     for i = 1, #sources do
-      sources[i]:subscribe(onNext(i), onError, onCompleted(i))
+      subscription[i] = sources[i]:subscribe(onNext(i), onError, onCompleted(i))
     end
+
+    return Subscription.create(function ()
+      for i = 1, #subscription do
+        if subscription[i] then subscription[i]:unsubscribe() end
+      end
+    end)
   end)
 end

tests/combineLatest.lua

@@ -4,6 +4,25 @@ describe('combineLatest', function()
     expect(observable).to.produce(1, 2, 3, 4, 5)
   end)
 
+  it('unsubscribes from the combined source observables', function()
+    local unsubscribeA = spy()
+    local subscriptionA = Rx.Subscription.create(unsubscribeA)
+    local observableA = Rx.Observable.create(function(observer)
+      return subscriptionA
+    end)
+
+    local unsubscribeB = spy()
+    local subscriptionB = Rx.Subscription.create(unsubscribeB)
+    local observableB = Rx.Observable.create(function(observer)
+      return subscriptionB
+    end)
+
+    local subscription = Rx.Observable.combineLatest(observableA, observableB):subscribe()
+    subscription:unsubscribe()
+    expect(#unsubscribeA).to.equal(1)
+    expect(#unsubscribeB).to.equal(1)
+  end)
+
   it('calls the combinator function with all values produced from all input observables once they have all produced a value', function()
     local observableA = Rx.Observable.of('a')
     local observableB = Rx.Observable.of('b')