Miscellaneous coverage improvements.

formula/src/main/java/com/instacart/formula/Cancelable.kt

@@ -3,16 +3,6 @@ package com.instacart.formula
 /**
  * Used within [Action] to receive a cancel event and perform clean up.
  */
-interface Cancelable {
-    companion object {
-        inline operator fun invoke(crossinline cancel: () -> Unit): Cancelable {
-            return object : Cancelable {
-                override fun cancel() {
-                    cancel()
-                }
-            }
-        }
-    }
-
+fun interface Cancelable {
     fun cancel()
 }

formula/src/main/java/com/instacart/formula/DeferredAction.kt

@@ -5,13 +5,13 @@ package com.instacart.formula
  */
 class DeferredAction<Event>(
     val key: Any,
-    val action: Action<Event>,
+    private val action: Action<Event>,
     // We use event listener for equality because it provides better equality performance
-    val initial: (Event) -> Unit
+    private val initial: (Event) -> Unit
 ) {
+    private var cancelable: Cancelable? = null
 
     internal var listener: (Event) -> Unit = initial
-    internal var cancelable: Cancelable? = null
 
     internal fun start() {
         cancelable = action.start() { message ->
@@ -24,22 +24,15 @@ class DeferredAction<Event>(
         cancelable = null
     }
 
+    /**
+     * Action equality is based on the [initial] listener.
+     */
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
-        if (javaClass != other?.javaClass) return false
-
-        other as DeferredAction<*>
-
-        if (initial != other.initial) return false
-
-        return true
+        return other is DeferredAction<*> && initial == other.initial
     }
 
     override fun hashCode(): Int {
         return initial.hashCode()
     }
-
-    fun keyAsString(): String {
-        return key.toString()
-    }
 }

formula/src/main/java/com/instacart/formula/FormulaContext.kt

@@ -123,12 +123,12 @@ abstract class FormulaContext<out Input, State> internal constructor(
     internal abstract fun <Event> eventListener(
         key: Any,
         useIndex: Boolean = true,
-        executionType: Transition.ExecutionType? = null,
+        executionType: Transition.ExecutionType?,
         transition: Transition<Input, State, Event>
     ): Listener<Event>
 
     // Internal key scope management
     @PublishedApi internal abstract fun enterScope(key: Any)
     @PublishedApi internal abstract fun endScope()
-    @PublishedApi internal abstract fun createScopedKey(type: KClass<*>, key: Any? = null): Any
+    @PublishedApi internal abstract fun createScopedKey(type: KClass<*>, key: Any?): Any
 }

formula/src/test/java/com/instacart/formula/DeferredActionTest.kt

@@ -0,0 +1,31 @@
+package com.instacart.formula
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+
+class DeferredActionTest {
+
+    @Test
+    fun `identity equality returns true`() {
+        val callback = { _: Unit -> }
+        val action = DeferredAction(key = "1", action = Action.onInit(), callback)
+        assertThat(action.equals(action)).isTrue()
+    }
+
+    @Test
+    fun `when class is different, equality returns false`() {
+        val callback = { _: Unit -> }
+        val action = DeferredAction(key = "1", action = Action.onInit(), callback)
+        assertThat(action).isNotEqualTo("string")
+    }
+
+    @Test
+    fun `when listeners are not equal, the actions are not equal`() {
+        val callback = { _: Unit -> }
+        val callback2 = { _: Unit -> }
+        val action1 = DeferredAction(key = "1", action = Action.onInit(), callback)
+        val action2 = DeferredAction(key = "1", action = Action.onInit(), callback2)
+
+        assertThat(action1).isNotEqualTo(action2)
+    }
+}

formula/src/test/java/com/instacart/formula/TransitionApiTest.kt

@@ -1,6 +1,7 @@
 package com.instacart.formula
 
 import com.google.common.truth.Truth
+import com.google.common.truth.Truth.assertThat
 import com.instacart.formula.internal.DelegateTransitionContext
 import com.instacart.formula.internal.toResult
 import com.instacart.formula.test.TestListener
@@ -11,18 +12,32 @@ class TransitionApiTest {
     @Test fun `none transition`() {
         val transition = Transition<Unit, Int, Unit> { none() }
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit)
-        Truth.assertThat(result).isEqualTo(Transition.Result.None)
+        assertThat(result).isEqualTo(Transition.Result.None)
     }
 
     @Test fun `none transition has no effects`() {
         val result = Transition.Result.None
-        Truth.assertThat(result.effects).isEmpty()
+        assertThat(result.effects).isEmpty()
+    }
+
+    @Test fun `state transition result with effect type but null effect`() {
+        val result = DelegateTransitionContext(Unit, 0)
+            .transition(1, Effect.Unconfined, null)
+
+        assertThat(result.state).isEqualTo(1)
+        assertThat(result.effects).isEmpty()
+    }
+
+    @Test fun `transition returns null if effect is null`() {
+        val result = DelegateTransitionContext(Unit, 0)
+            .transition(Effect.Unconfined, null)
+        assertThat(result).isEqualTo(Transition.Result.None)
     }
 
     @Test fun `stateful transition`() {
         val transition = Transition<Unit, Int, Unit> { transition(state + 1) }
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(1)
+        assertThat(result.state).isEqualTo(1)
     }
 
     @Test fun `stateful transition with effects`() {
@@ -34,7 +49,7 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(1)
+        assertThat(result.state).isEqualTo(1)
 
         result.assertAndExecuteEffects()
         testListener.assertTimesCalled(1)
@@ -59,7 +74,7 @@ class TransitionApiTest {
             delegate(AddTransition(), 5)
         }
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(5)
+        assertThat(result.state).isEqualTo(5)
     }
 
     @Test fun `transition combine none transition with stateful transition`() {
@@ -68,7 +83,7 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(1)
+        assertThat(result.state).isEqualTo(1)
     }
 
     @Test fun `transition combine only effects transition with stateful transition`() {
@@ -79,7 +94,7 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(1)
+        assertThat(result.state).isEqualTo(1)
 
         result.assertAndExecuteEffects()
         testListener.assertTimesCalled(1)
@@ -91,7 +106,7 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(2)
+        assertThat(result.state).isEqualTo(2)
     }
 
     @Test fun `transition combine keeps effect order`() {
@@ -102,10 +117,10 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(2)
+        assertThat(result.state).isEqualTo(2)
 
         result.assertAndExecuteEffects()
-        Truth.assertThat(listener.values()).containsExactly(1, 2).inOrder()
+        assertThat(listener.values()).containsExactly(1, 2).inOrder()
     }
 
     @Test fun `state andThen another stateful result`() {
@@ -114,7 +129,7 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(3)
+        assertThat(result.state).isEqualTo(3)
     }
 
     @Test fun `state andThen empty result`() {
@@ -124,16 +139,16 @@ class TransitionApiTest {
         }
 
         val result = transition.toResult(DelegateTransitionContext(Unit, 0), Unit).assertStateful()
-        Truth.assertThat(result.state).isEqualTo(1)
+        assertThat(result.state).isEqualTo(1)
     }
 
     private fun <State> Transition.Result<State>.assertStateful(): Transition.Result.Stateful<State> {
-        Truth.assertThat(this).isInstanceOf(Transition.Result.Stateful::class.java)
+        assertThat(this).isInstanceOf(Transition.Result.Stateful::class.java)
         return this as Transition.Result.Stateful<State>
     }
 
     private fun <State> Transition.Result<State>.assertAndExecuteEffects() {
-        Truth.assertThat(effects).isNotEmpty()
+        assertThat(effects).isNotEmpty()
         for (effect in effects) {
             effect.executable()
         }