Fix assertion descriptions (#2405)

* Fix assertion descriptions

Move return statement to the end of define()

* ospec: Fix assertion definitions

* Fix typo in assertion

* Add test for descriptions being returned on fail

* Reference result instead of self in returned description method

* Fix style errors

docs/change-log.md

@@ -123,6 +123,7 @@ _2019-07-24_
 #### Bug fixes
 
 - API: `m.route.set()` causes all mount points to be redrawn ([#1592](https://github.com/MithrilJS/mithril.js/pull/1592))
+- ospec: Fix assertion definitions breaking on comparison failure
 - render/attrs: Using style objects in hyperscript calls will now properly diff style properties from one render to another as opposed to re-writing all element style properties every render.
 - render/attrs All vnodes attributes are properly removed when absent or set to `null` or `undefined` [#1804](https://github.com/MithrilJS/mithril.js/issues/1804) [#2082](https://github.com/MithrilJS/mithril.js/issues/2082) ([#1865](https://github.com/MithrilJS/mithril.js/pull/1865), [#2130](https://github.com/MithrilJS/mithril.js/pull/2130))
 - render/core: Render state correctly on select change event [#1916](https://github.com/MithrilJS/mithril.js/issues/1916) ([#1918](https://github.com/MithrilJS/mithril.js/pull/1918) [@robinchew](https://github.com/robinchew), [#2052](https://github.com/MithrilJS/mithril.js/pull/2052))

ospec/ospec.js

@@ -291,8 +291,11 @@ else window.o = m()
 			var message = serialize(self.value) + "\n  " + verb + "\n" + serialize(value)
 			if (compare(self.value, value)) succeed(self, message)
 			else fail(self, message)
+			var result = results[self.i]
 			return function(message) {
-				if (!self.pass) self.message = message + "\n\n" + self.message
+				if (!result.pass) {
+					result.message = message + "\n\n" + result.message
+				}
 			}
 		}
 	}

ospec/tests/test-ospec.js

@@ -299,7 +299,7 @@ o.spec("ospec", function() {
 		})
 	})
 
-	o.spec("throwing in test context is recoreded as a failure", function() {
+	o.spec("throwing in test context is recorded as a failure", function() {
 		var oo
 		o.beforeEach(function(){oo = o.new()})
 		o.afterEach(function() {
@@ -659,6 +659,24 @@ o.spec("ospec", function() {
 			})
 		})
 	})
+
+	o.spec("descriptions", function() {
+		o("description returned on failure", function(done) {
+			var oo = o.new()
+			oo("no description", function() {
+				oo(1).equals(2)
+			})
+			oo("description", function() {
+				oo(1).equals(2)("howdy")
+			})
+			oo.run(function(results) {
+				o(results.length).equals(2)
+				o(results[1].message).equals(`howdy\n\n${results[0].message}`)
+				o(results[1].pass).equals(false)
+				done()
+			})
+		})
+	})
 })
 o.spec("the done parser", function() {
 	o("accepts non-English names", function() {