Merge branch 'feat/state-combinator' of github.com:motorcyclets/motor…

…cycle into feat/state-combinator

Signed-off-by: Frederik Krautwald <fkrautwald@gmail.com>

packages/stream/src/combinators/state.test.ts

@@ -15,6 +15,33 @@ export const test: Test = describe(`state`, [
 
       return collectEvents(sut).then(equal(expected))
     }),
+
+    it(`does not emit repeated values`, ({ equal }) => {
+      const a$ = mergeArray([at(0, 0), at(100, 100), at(200, 200)])
+      const b$ = mergeArray([at(1, 1), at(2, 0)])
+
+      const expected = [0, 1, 100, 101, 200, 201]
+      const sut = state(add, a$, b$)
+
+      return collectEvents(sut).then(equal(expected))
+    }),
+
+    it(`emits latest value to late subscribers`, ({ equal }, done) => {
+      const a$ = mergeArray([at(0, 0), at(500, 100), at(1000, 200)])
+      const b$ = mergeArray([at(150, 1), at(300, 2)])
+
+      const sut = state(add, a$, b$)
+
+      setTimeout(() => {
+        const expected = [100, 101, 103, 200, 201, 203]
+        collectEvents(sut)
+          .then(equal(expected))
+          .then(() => done())
+          .catch(done)
+      }, 550)
+
+      collectEvents(sut)
+    }),
   ]),
 ])
 

packages/stream/src/combinators/state.ts

@@ -1,6 +1,8 @@
 import { Stream } from '@motorcycle/types'
 import { curry3 } from '167'
+import { hold } from './hold'
 import { scan } from './scan'
+import { skipRepeats } from './skipRepeats'
 import { switchMap } from './switchMap'
 
 /**
@@ -40,7 +42,7 @@ function __state<A, B>(
   seed$: Stream<B>,
   values$: Stream<A>
 ): Stream<B> {
-  return switchMap(seed => scan(f, seed, values$), seed$)
+  return hold(skipRepeats(switchMap(seed => scan(f, seed, values$), seed$)))
 }
 
 export interface State {