xpath: [incorrect] support for indexed-repeat function

.changeset/four-bats-kick.md

@@ -0,0 +1,7 @@
+---
+"@getodk/scenario": patch
+"@getodk/xforms-engine": patch
+"@getodk/xpath": patch
+---
+
+xpath: support for `indexed-repeat` function

packages/scenario/src/jr/Scenario.ts

@@ -64,6 +64,10 @@ interface CreateNewRepeatAssertedReferenceOptions {
 	readonly assertCurrentReference: string;
 }
 
+interface SetPositionalStateOptions {
+	readonly createMissingRepeatInstances?: boolean;
+}
+
 // prettier-ignore
 type GetQuestionAtIndexParameters<
 	ExpectedQuestionType extends QuestionNodeType
@@ -140,7 +144,8 @@ export class Scenario {
 	readonly formName: string;
 	readonly instanceRoot: RootNode;
 
-	private readonly getPositionalEvents: Accessor<PositionalEvents>;
+	protected readonly getPositionalEvents: Accessor<PositionalEvents>;
+	protected readonly getEventPosition: Accessor<number>;
 	private readonly setEventPosition: Setter<number>;
 
 	protected readonly getSelectedPositionalEvent: Accessor<AnyPositionalEvent>;
@@ -151,14 +156,15 @@ export class Scenario {
 		this.formName = formName;
 		this.instanceRoot = instanceRoot;
 
-		const [eventPosition, setEventPosition] = createSignal(0);
+		const [getEventPosition, setEventPosition] = createSignal(0);
 
 		this.getPositionalEvents = () => getPositionalEvents(instanceRoot);
+		this.getEventPosition = getEventPosition;
 		this.setEventPosition = setEventPosition;
 
 		this.getSelectedPositionalEvent = createMemo(() => {
 			const events = getPositionalEvents(instanceRoot);
-			const position = eventPosition();
+			const position = getEventPosition();
 			const event = events[position];
 
 			if (event == null) {
@@ -288,13 +294,73 @@ export class Scenario {
 		return this.setNonTerminalEventPosition(increment, expectReference);
 	}
 
-	private setPositionalStateToReference(reference: string): AnyPositionalEvent {
+	private createMissingRepeatInstances(reference: string): void {
+		let tempReference = reference;
+		let indexedReference: string | null = null;
+
+		const trailingPositionalPredicatePattern = /\[\d+\]$/;
+
+		do {
+			if (trailingPositionalPredicatePattern.test(tempReference)) {
+				indexedReference = tempReference;
+			} else {
+				tempReference = tempReference.replace(/\/[^/]+$/, '');
+
+				if (tempReference === '') {
+					break;
+				}
+			}
+		} while (indexedReference == null);
+
+		if (indexedReference == null) {
+			return;
+		}
+
+		const repeatRangeReference = indexedReference.replace(trailingPositionalPredicatePattern, '');
+
+		const positionalPredicate = indexedReference.replace(/^.*\[(\d+)\]$/, '$1');
+		const count = parseInt(positionalPredicate, 10);
+
+		if (count < 1) {
+			return;
+		}
+
+		const repeatRange = this.getInstanceNode(repeatRangeReference);
+
+		if (repeatRange.nodeType !== 'repeat-range') {
+			throw 'todo';
+		}
+
+		const repeatBodyDefinition = repeatRange.definition.bodyElement;
+
+		if (repeatBodyDefinition.countExpression != null || repeatBodyDefinition.isFixedCount) {
+			return;
+		}
+
+		const instances = repeatRange.currentState.children.length;
+		const delta = count - instances;
+
+		for (let i = 0; i < delta; i += 1) {
+			this.createNewRepeat(repeatRangeReference);
+		}
+	}
+
+	private setPositionalStateToReference(
+		reference: string,
+		options: SetPositionalStateOptions = {}
+	): AnyPositionalEvent {
 		const events = this.getPositionalEvents();
 		const index = events.findIndex(({ node }) => {
 			return node?.currentState.reference === reference;
 		});
 
 		if (index === -1) {
+			if (options?.createMissingRepeatInstances) {
+				this.createMissingRepeatInstances(reference);
+
+				return this.setPositionalStateToReference(reference);
+			}
+
 			throw new Error(
 				`Setting answer to ${reference} failed: could not locate question/positional event with that reference.`
 			);
@@ -304,7 +370,9 @@ export class Scenario {
 	}
 
 	private answerSelect(reference: string, ...selectionValues: string[]): ComparableAnswer {
-		const event = this.setPositionalStateToReference(reference);
+		const event = this.setPositionalStateToReference(reference, {
+			createMissingRepeatInstances: true,
+		});
 
 		if (!isQuestionEventOfType(event, 'select')) {
 			throw new Error(
@@ -315,6 +383,15 @@ export class Scenario {
 		return event.answerQuestion(new SelectValuesAnswer(selectionValues));
 	}
 
+	/**
+	 * **PORTING NOTES**
+	 *
+	 * Per JavaRosa:
+	 *
+	 * > This method has side effects:
+	 * > - It will create all the required middle and end repeat group instances
+	 * > - It changes the current form index
+	 */
 	answer(...args: AnswerParameters): unknown {
 		if (isAnswerSelectParams(args)) {
 			return this.answerSelect(...args);
@@ -335,7 +412,9 @@ export class Scenario {
 		} else if (typeof arg0 === 'string') {
 			const reference = arg0;
 
-			event = this.setPositionalStateToReference(reference);
+			event = this.setPositionalStateToReference(reference, {
+				createMissingRepeatInstances: true,
+			});
 			value = arg1;
 		} else {
 			throw new Error('Unsupported `answer` overload call');
@@ -371,7 +450,7 @@ export class Scenario {
 		const node = getNodeForReference(this.instanceRoot, reference);
 
 		if (node == null) {
-			throw new Error(`No "answer" node for reference: ${reference}`);
+			throw new Error(`No instance node for reference: ${reference}`);
 		}
 
 		return node;

packages/scenario/test/repeat.test.ts

@@ -2262,15 +2262,18 @@ describe('Tests ported from JavaRosa - repeats', () => {
 		/**
 		 * **PORTING NOTES**
 		 *
-		 * - Fails pending implementation of `indexed-repeat` XPath function.
-		 *
 		 * - Parameters adapted to match values in JavaRosa. Note that the
 		 *   parameters are passed as {@link options} rather than destructured. Java
 		 *   lets you reference `group` (the class property) and `group` (the
 		 *   imported static method) in the same scope. TypeScript/JavaScript don't
 		 *   let you do that... which is fine, because doing that is really weird!
+		 *
+		 * - `answer` calls updated to omit superfluous position predicate on
+		 *   the non-repeat `some-group` step (we do this lookup by `reference`,
+		 *   not evaluating arbitrary XPath expressions to identify the question
+		 *   being answered).
 		 */
-		it.fails.each<IndexedRepeatRelativeRefsOptions>(parameters)('$testName', async (options) => {
+		it.each<IndexedRepeatRelativeRefsOptions>(parameters)('$testName', async (options) => {
 			const scenario = await Scenario.init(
 				'Some form',
 				html(
@@ -2311,9 +2314,14 @@ describe('Tests ported from JavaRosa - repeats', () => {
 				)
 			);
 
-			scenario.answer('/data/some-group[1]/item[1]/value', 11);
-			scenario.answer('/data/some-group[1]/item[2]/value', 22);
-			scenario.answer('/data/some-group[1]/item[3]/value', 33);
+			// scenario.answer('/data/some-group[1]/item[1]/value', 11);
+			scenario.answer('/data/some-group/item[1]/value', 11);
+
+			// scenario.answer('/data/some-group[1]/item[2]/value', 22);
+			scenario.answer('/data/some-group/item[2]/value', 22);
+
+			// scenario.answer('/data/some-group[1]/item[3]/value', 33);
+			scenario.answer('/data/some-group/item[3]/value', 33);
 
 			expect(scenario.answerOf('/data/total-items')).toEqualAnswer(intAnswer(3));
 			expect(scenario.answerOf('/data/some-group/last-value')).toEqualAnswer(intAnswer(33));

packages/scenario/test/select.test.ts

@@ -376,16 +376,8 @@ describe('DynamicSelectUpdateTest.java', () => {
 		});
 	});
 
-	/**
-	 * **PORTING NOTES**
-	 *
-	 * This currently fails because repeat-based itemsets are broken more
-	 * generally. As with the above sub-suite, the last assertion is a reference
-	 * check and will always pass. Once repeat-based itemsets are fixed, we'll
-	 * want to consider whether this test should be implemented differently too.
-	 */
 	describe('select with repeat as trigger', () => {
-		it.fails('recomputes [the] choice list at every request', async () => {
+		it('recomputes [the] choice list at every request', async () => {
 			const scenario = await Scenario.init(
 				'Select with repeat trigger',
 				html(
@@ -417,7 +409,8 @@ describe('DynamicSelectUpdateTest.java', () => {
 
 			expect(choices.size()).toBe(2);
 
-			// Because of the repeat trigger in the count expression, choices should be recomputed every time they're requested
+			// JR: Because of the repeat trigger in the count expression, choices
+			// should be recomputed every time they're requested
 			expect(scenario.choicesOf('/data/select')).not.toBe(choices);
 		});
 	});