Implement termination without executing local transition queue and do…

…cs update
instacart · Jun 5, 2024 · 8355fdb · 8355fdb
1 parent 15351c1
commit 8355fdb
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Showing 4 changed files with 34 additions and 8 deletions.
diff --git a/formula/src/main/java/com/instacart/formula/FormulaContext.kt b/formula/src/main/java/com/instacart/formula/FormulaContext.kt
@@ -93,6 +93,20 @@ abstract class FormulaContext<out Input, State> internal constructor(
         return child(formula, Unit)
     }
 
+    /**
+     * A convenience method to run a formula that takes no input. Returns the latest output of
+     * the [child] formula or null if the child formula has encountered an exception. Child formulas
+     * that encounter exceptions will be be terminated and will not be run again. Formula runtime
+     * ensures the [formula] is running, manages its internal state and will trigger `evaluate`
+     * if needed.
+     */
+    fun <ChildOutput> child(
+        formula: IFormula<Unit, ChildOutput>,
+        onError: (Throwable) -> Unit,
+    ): ChildOutput? {
+        return child(formula, Unit, onError)
+    }
+
     /**
      * Returns the latest output of the [child] formula. Formula runtime ensures the [child]
      * is running, manages its internal state and will trigger `evaluate` if needed.

diff --git a/formula/src/main/java/com/instacart/formula/internal/ChildrenManager.kt b/formula/src/main/java/com/instacart/formula/internal/ChildrenManager.kt
@@ -45,8 +45,8 @@ internal class ChildrenManager(
         children?.forEachValue { it.markAsTerminated() }
     }
 
-    fun performTerminationSideEffects() {
-        children?.forEachValue { it.performTerminationSideEffects() }
+    fun performTerminationSideEffects(executeTransitionQueue: Boolean) {
+        children?.forEachValue { it.performTerminationSideEffects(executeTransitionQueue) }
     }
 
     fun <ChildInput, ChildOutput> findOrInitChild(

diff --git a/formula/src/main/java/com/instacart/formula/internal/FormulaManager.kt b/formula/src/main/java/com/instacart/formula/internal/FormulaManager.kt
@@ -29,6 +29,11 @@ interface FormulaManager<Input, Output> {
 
     /**
      * Called when we are ready to perform termination side-effects.
+     * @param executeTransitionQueue whether the formula should execute remaining transitions
+     *      that accumulated while it was running. False is passed in the case where the
+     *      formula threw an exception and we want to avoid executubg transitions that have
+     *      an elevated chance of also throwing an exception. Other termination side
+     *      effects such as listener and action termination still happen.
      */
-    fun performTerminationSideEffects()
+    fun performTerminationSideEffects(executeTransitionQueue: Boolean = true)
 }
diff --git a/formula/src/main/java/com/instacart/formula/internal/FormulaManagerImpl.kt b/formula/src/main/java/com/instacart/formula/internal/FormulaManagerImpl.kt
@@ -265,6 +265,9 @@ internal class FormulaManagerImpl<Input, State, Output>(
         manager.setValidationRun(isValidationEnabled)
 
         return try {
+            // If manager.run(input) previously threw an exception it would be marked as
+            // terminated in the catch block. We avoid running it again because there is a decent
+            // chance it will continue to throw the same exception and cause performance issues
             if (!manager.isTerminated()) {
                 manager.run(input).output
             } else {
@@ -285,13 +288,17 @@ internal class FormulaManagerImpl<Input, State, Output>(
         childrenManager?.markAsTerminated()
     }
 
-    override fun performTerminationSideEffects() {
-        childrenManager?.performTerminationSideEffects()
+    override fun performTerminationSideEffects(executeTransitionQueue: Boolean) {
+        childrenManager?.performTerminationSideEffects(executeTransitionQueue)
         actionManager.terminate()
 
-        // Execute deferred transitions
-        while (transitionQueue.isNotEmpty()) {
-            transitionQueue.pollFirst().execute()
+        if (executeTransitionQueue) {
+            // Execute deferred transitions
+            while (transitionQueue.isNotEmpty()) {
+                transitionQueue.pollFirst().execute()
+            }
+        } else {
+            transitionQueue.clear()
         }
 
         listeners.disableAll()