Rewrite repeat operator to handle 0 case correctly and not rely on magic numbers (#356)

* Sketch interface for finite/inifinite variants

* CRTP deriving finite/infinite from base

* Fully rewrite repeat implementation

* Fix description and comments in repeat

* Test repeat(0) case

* Make 0 handling with completion when the input sequence complete

* Return immidiately empty sequence instead on first on_completed

* Return immidiately empty sequence instead on first on_completed

* Update param description for repeat 0 case

* repeat(0): never call on.next(), but call on.completed()

* Test: no subscriptions are made when repeat(0)

1 files changed, 41 insertions, 0 deletions

diff --git a/Rx/v2/test/operators/repeat.cpp b/Rx/v2/test/operators/repeat.cpp
index 80c3c87..0aa9598 100644
--- a/Rx/v2/test/operators/repeat.cpp
+++ b/Rx/v2/test/operators/repeat.cpp
@@ -56,6 +56,47 @@ SCENARIO("repeat, basic test", "[repeat][operators]"){
     }
 }
 
+SCENARIO("repeat, 0 times case", "[repeat][operators]"){
+    GIVEN("cold observable of 3 ints."){
+        auto sc = rxsc::make_test();
+        auto w = sc.create_worker();
+        const rxsc::test::messages<int> on;
+
+        auto xs = sc.make_cold_observable({
+            on.next(100, 1),
+            on.next(150, 2),
+            on.next(200, 3),
+            on.completed(250)
+        });
+
+        WHEN("repeat zero times is launched"){
+
+            auto res = w.start(
+                [&]() {
+                    return xs
+                        | rxo::repeat(0)
+                        // forget type to workaround lambda deduction bug on msvc 2013
+                        | rxo::as_dynamic();
+                }
+            );
+
+            THEN("the output should be empty"){
+              auto required = rxu::to_vector({
+                  on.completed(200)
+                    });
+              auto actual = res.get_observer().messages();
+              REQUIRE(required == actual);
+            }
+
+            THEN("no subscriptions in repeat(0) variant that skips on.next()"){
+              auto required = std::vector<rxcpp::notifications::subscription>();
+              auto actual = xs.subscriptions();
+              REQUIRE(required == actual);
+            }
+        }
+    }
+}
+
 SCENARIO("repeat, infinite observable test", "[repeat][operators]"){
     GIVEN("cold observable of 3 ints that never completes."){
         auto sc = rxsc::make_test();