Do not store task result when item deletes itself

src/database-backends/index.js

@@ -159,12 +159,13 @@ module.exports = function (state) {
 			},
 			forItem: function (_options) {
 				// FIXME: Proper validation rules here for the other fields as well
-				let { item, task, mutationQueue, readTX, simulate } = validateOptions(arguments, {
+				let { item, task, mutationQueue, readTX, simulate, onDeleteSelf } = validateOptions(arguments, {
 					item: anything,
 					task: [ required, isTask ],
 					mutationQueue: anything,
 					readTX: maybeTX,
-					simulate: anything
+					simulate: anything,
+					onDeleteSelf: isFunction
 				});
 
 				// We create a new instance of the actual API for every item being processed. This is necessary because some of the input arguments will default to item-specific values, and some of the logic is dependent on task-specific metadata. This is a more efficient (and understandable) approach than pretending the API is stateless and then separately wrapping the API *again* for every individual item with a whole separate layer of input validation rules.
@@ -261,6 +262,11 @@ module.exports = function (state) {
 							]
 						});
 	
+						if (options.id === item.id) {
+							// This hook is necessary to allow the task kernel to skip certain operations in this case, eg. storing the task result - it would be redundant, and reference a now non-existent item.
+							onDeleteSelf();
+						}
+
 						return mutableOperation((tx) => {
 							return backend.deleteItem(tx, options);
 						});
@@ -294,6 +300,7 @@ module.exports = function (state) {
 
 					updateData: function (_options) {
 						// NOTE: This is a semantically self-describing convenience wrapper for `storeItem` that updates the currently-being-processed item
+						// TODO: Have a dedicated alias and/or signature (for this function) for the common case of "just add a few attributes to whatever is already there"? ie. a shallow merge
 						let [ options ] = validateArguments(arguments, {
 							options: [ required, wrapValueAsOption("update"), {
 								id: [ defaultTo(item.id), isString ],

src/run-task.js

@@ -8,7 +8,14 @@ const logStatus = require("./util/log-status");
 module.exports = function ({ backend }) {
 	return function runTask(task, item) {
 		let queue = [];
-		let api = backend.forItem({ task: task, item: item, mutationQueue: queue });
+		let itemIsDeleted = false;
+
+		let api = backend.forItem({
+			task: task,
+			item: item,
+			mutationQueue: queue,
+			onDeleteSelf: () => { itemIsDeleted = true; }
+		});
 	
 		return Promise.try(() => {
 			// TODO: Standardize logging control/levels interface, also for library use
@@ -30,7 +37,9 @@ module.exports = function ({ backend }) {
 				});
 			});
 		}).then(async () => {
-			await api.internal.markTaskCompleted();
+			if (!itemIsDeleted) {
+				await api.internal.markTaskCompleted();
+			}
 
 			if (!process.env.SRAP_QUIET) {
 				logStatus(task, chalk.bold.green, "completed", item.id);