Fix #2601 (#2603)

Fix issue where ending a stream in the middle of a stream callback would result in erroneous parent stream state for the rest of that emit.

docs/change-log.md

@@ -30,6 +30,7 @@
 - Add `m.censor`. ([#2538](https://github.com/MithrilJS/mithril.js/pull/2538) [@isiahmeadows](https://github.com/isiahmeadows))
 - Re-add stream bundles. ([#2539](https://github.com/MithrilJS/mithril.js/pull/2539) [@isiahmeadows](https://github.com/isiahmeadows))
 - Remove extra isLifecycleMethod call from removeAttr. ([#2594](https://github.com/MithrilJS/mithril.js/pull/2594) [@ZeikJT](https://github.com/zeikjt))
+- Fix issue where ending a stream in the middle of a stream callback would result in erroneous parent stream state for the rest of that emit. ([#2603](https://github.com/MithrilJS/mithril.js/pull/2603) [@isiahmeadows](https://github.com/isiahmeadows))
 
 Important note: if you were using any of these undocumented tools, they are no longer available as of this release. This is not considered a breaking change as they were written for internal usage and as of v2 are all 100% unsupported in userland.
 

stream/stream.js

@@ -29,7 +29,11 @@ function Stream(value) {
 			if (open(stream)) {
 				stream._changing()
 				stream._state = "active"
-				dependentStreams.forEach(function(s, i) { s(dependentFns[i](value)) })
+				// Cloning the list to ensure it's still iterated in intended
+				// order
+				dependentStreams.slice().forEach(function(s, i) {
+					if (open(s)) s(this[i](value))
+				}, dependentFns.slice())
 			}
 		}
 

stream/tests/test-stream.js

@@ -494,6 +494,40 @@ o.spec("stream", function() {
 			stream(2)
 			o(stream()).equals(2)
 		})
+		// https://github.com/MithrilJS/mithril.js/issues/2601
+		o("ended stream doesn't affect emit of subsequent streams", function() {
+			const refreshing = Stream()
+			const o1Received = []
+			const waitingReceived = []
+			const o2Received = []
+			const o3Received = []
+			const o4Received = []
+
+			/* eslint-disable array-callback-return */
+			refreshing.map(function(v) { o1Received.push(v) })
+
+			const waiting = refreshing.map(function(v) {
+				waitingReceived.push(v)
+				if (v === false) {
+					waiting.end(true)
+				}
+			})
+
+			refreshing.map(function(v) { o2Received.push(v) })
+			refreshing.map(function(v) { o3Received.push(v) })
+			refreshing.map(function(v) { o4Received.push(v) })
+			/* eslint-enable array-callback-return */
+
+			refreshing(true)
+			refreshing(false)
+			refreshing("more")
+
+			o(o1Received).deepEquals([true, false, "more"])
+			o(waitingReceived).deepEquals([true, false])
+			o(o2Received).deepEquals([true, false, "more"])
+			o(o3Received).deepEquals([true, false, "more"])
+			o(o4Received).deepEquals([true, false, "more"])
+		})
 	})
 	o.spec("toJSON", function() {
 		o("works", function() {