stacks are created without unnecessary sequences

a single level stack is now just a level
and a a single item in single level stack  is now just an item
this makes the YAML less verbose

package.json

@@ -89,5 +89,5 @@
 		"spellcheck": "find -type f \\( -name \"*.js\" -or -name \"*.md\" \\) ! -path \"./dist/*\" ! -path \"./dist/**/*\" ! -path \"./node_modules/**/*\" ! -path \"./test-coverage/**/*\" -exec npx cspell {} +",
 		"test": "npx jest --runInBand"
 	},
-	"version": "4.0.0"
+	"version": "4.1.0"
 }

stacking/createStackWhenIdentifierOrItemOrLevelOrAddWhenStack/createLevelMap/getStackOrSingleLevelOrSingleItem.js

@@ -0,0 +1,26 @@
+module.exports =
+	stack => {
+		return whenSingleLevel() || stack;
+
+		function whenSingleLevel() {
+			return (
+				stack.length === 1
+				&&
+				getLevelOrSingleItem(stack[0])
+			);
+		}
+	};
+
+function getLevelOrSingleItem(
+	level,
+) {
+	return whenSingleItem() || level;
+
+	function whenSingleItem() {
+		return (
+			level.length === 1
+			&&
+			level[0]
+		);
+	}
+}

stacking/createStackWhenIdentifierOrItemOrLevelOrAddWhenStack/createLevelMap.js → stacking/createStackWhenIdentifierOrItemOrLevelOrAddWhenStack/createLevelMap/index.js

@@ -1,6 +1,8 @@
 require("array.prototype.flat")
 .shim();
 
+const getStackOrSingleLevelOrSingleItem = require("./getStackOrSingleLevelOrSingleItem");
+
 module.exports =
 	({
 		addMissing,
@@ -25,7 +27,9 @@ module.exports =
 			return (
 				itemsByIdentifiersInNewLevel.size || addMissing
 				?
-				identifiersInNewStack.reduce(aggregate, [])
+				getStackOrSingleLevelOrSingleItem(
+					identifiersInNewStack.reduce(aggregate, []),
+				)
 				:
 				getExistingWhenNoNewLevels()
 			);

stacking/createStackWhenIdentifierOrItemOrLevelOrAddWhenStack/test.js

@@ -74,6 +74,13 @@ test.each(
 				[ "itemNotSpecified" ],
 			],
 		],
+		[
+			{
+				identifierOrItemOrLevelOrStack: "itemSpecified",
+				identifiersInNewStack: [ "itemSpecified" ],
+			},
+			"itemSpecified",
+		],
 		[
 			{
 				identifierOrItemOrLevelOrStack: [ "itemSpecified", "itemNotSpecified" ],
@@ -179,7 +186,7 @@ test.each(
 				identifierOrItemOrLevelOrStack: [ "item1", "item2" ],
 				identifiersInNewStack: [ [ "item1", "item2" ] ],
 			},
-			[ [ "item1", "item2" ] ],
+			[ "item1", "item2" ],
 		],
 		[
 			{
@@ -245,7 +252,7 @@ test.each(
 				identifierOrItemOrLevelOrStack: [ "item1", [] ],
 				identifiersInNewStack: [ "item1" ],
 			},
-			[ [ "item1" ] ],
+			"item1",
 		],
 	],
 )(