fix same-day calendar due duplicates

docs/releases/unreleased.md

@@ -48,6 +48,7 @@ When a change has user-facing documentation, include a canonical tasknotes.dev l
 ## Fixed
 
 - (#1976) Fixed embedded Calendar and Agenda Bases so "Navigate to date from property" can use the containing note's date property when the Base rows do not have that property. Thanks to @matesvecenik for reporting this.
+- (#1977) Fixed Calendar and Agenda views showing duplicate all-day entries when a task's scheduled date and due date are the same day. Timed due dates on the same day still show as separate deadline markers. Thanks to @pdgBC for reporting this.
 - (#216) Improved inline conversion for Tasks plugin task lines, including Dataview-style fields, priority markers, recurrence text, date aliases, block links, and safer trailing-field parsing. Thanks to @ksdavidc for the request, @natleahh for the Dataview example, and @hangryscribe3 and @nayatiuh for the discussion.
 - (#1974) Stopped Calendar and Agenda property-based events from logging date parse errors for entries that do not have the selected date property. Thanks to @Jomo94 for suggesting completed-date Agenda events.
 - (#1973) Reduced unnecessary Calendar view recreations when external calendar providers are reported in a different order, and preserved Calendar scroll position when a config-driven refresh has to recreate the view. Thanks to @e-zz for reporting this.

src/bases/calendar-core.ts

@@ -840,6 +840,15 @@ function replaceDatePartPreservingTime(value: string, datePart: string): string
 	return timePart ? `${datePart}T${timePart}` : datePart;
 }
 
+function hasDateOnlyDueOnScheduledDay(task: TaskInfo): boolean {
+	return Boolean(
+		task.scheduled &&
+			task.due &&
+			!hasTimeComponent(task.due) &&
+			getDatePart(task.scheduled) === getDatePart(task.due)
+	);
+}
+
 function createRecurringScheduledToDueSpanEvents(
 	task: TaskInfo,
 	instanceDate: string,
@@ -1505,7 +1514,8 @@ export async function generateCalendarEvents(
 		task: TaskInfo,
 		includeScheduled: boolean,
 		allowScheduledToDueSpan: boolean,
-		includeDue = showDue
+		includeDue = showDue,
+		hasGeneratedScheduledLayer = false
 	): void => {
 		let showedSpan = false;
 		if (allowScheduledToDueSpan && showScheduledToDueSpan && task.scheduled && task.due) {
@@ -1534,7 +1544,13 @@ export async function generateCalendarEvents(
 			}
 		}
 
-		if (includeDue && task.due) {
+		const shouldSuppressDateOnlyDue =
+			includeDue &&
+			(includeScheduled || hasGeneratedScheduledLayer) &&
+			hasDateOnlyDueOnScheduledDay(task);
+		const shouldShowDue = includeDue && !shouldSuppressDateOnlyDue;
+
+		if (shouldShowDue && task.due) {
 			if (isDateInVisibleRange(task.due, visibleStart, visibleEnd)) {
 				const dueEvent = createDueEvent(task, plugin);
 				if (dueEvent) {
@@ -1551,6 +1567,7 @@ export async function generateCalendarEvents(
 				let includeStandaloneScheduled = showScheduled;
 				let includeStandaloneDue = showDue;
 				let allowScheduledToDueSpan = true;
+				let hasGeneratedScheduledLayer = false;
 
 				if (
 					(showRecurring ||
@@ -1578,6 +1595,7 @@ export async function generateCalendarEvents(
 						);
 						events.push(...recurringEvents);
 						if (showRecurring) {
+							hasGeneratedScheduledLayer = recurringEvents.length > 0;
 							includeStandaloneScheduled = false;
 							allowScheduledToDueSpan = false;
 							if (
@@ -1596,7 +1614,8 @@ export async function generateCalendarEvents(
 					task,
 					includeStandaloneScheduled,
 					allowScheduledToDueSpan,
-					includeStandaloneDue
+					includeStandaloneDue,
+					hasGeneratedScheduledLayer
 				);
 			} else {
 				// Handle non-recurring tasks with date range filtering

tests/unit/issues/issue-1977-calendar-same-day-scheduled-due.test.ts

@@ -0,0 +1,106 @@
+/**
+ * Issue #1977: Calendar and Agenda should not duplicate date-only tasks when
+ * the scheduled and due dates are the same day.
+ *
+ * @see https://github.com/callumalpass/tasknotes/issues/1977
+ */
+
+import { generateCalendarEvents, type CalendarEvent } from "../../../src/bases/calendar-core";
+import type TaskNotesPlugin from "../../../src/main";
+import { TaskFactory } from "../../helpers/mock-factories";
+
+function createPlugin(): TaskNotesPlugin {
+	return {
+		priorityManager: {
+			getPriorityConfig: jest.fn().mockReturnValue({ color: "#6366f1" }),
+		},
+		statusManager: {
+			isCompletedStatus: jest.fn().mockReturnValue(false),
+		},
+	} as unknown as TaskNotesPlugin;
+}
+
+function eventTypes(events: CalendarEvent[]): string[] {
+	return events.map((event) => event.extendedProps.eventType).sort();
+}
+
+describe("Issue #1977: same-day scheduled and due Calendar duplicates", () => {
+	const plugin = createPlugin();
+
+	it("renders one task event when date-only scheduled and due values are the same day", async () => {
+		const task = TaskFactory.createTask({
+			title: "Same day task",
+			path: "Tasks/same-day.md",
+			scheduled: "2026-05-31",
+			due: "2026-05-31",
+		});
+
+		const events = await generateCalendarEvents([task], plugin, {
+			showScheduled: true,
+			showDue: true,
+			showRecurring: false,
+			showTimeEntries: false,
+		});
+
+		expect(eventTypes(events)).toEqual(["scheduled"]);
+		expect(events[0]).toMatchObject({
+			id: "scheduled-Tasks/same-day.md",
+			start: "2026-05-31",
+			allDay: true,
+		});
+	});
+
+	it("keeps separate due events when the due value adds a distinct time", async () => {
+		const task = TaskFactory.createTask({
+			title: "Timed deadline",
+			path: "Tasks/timed-deadline.md",
+			scheduled: "2026-05-31",
+			due: "2026-05-31T17:00",
+		});
+
+		const events = await generateCalendarEvents([task], plugin, {
+			showScheduled: true,
+			showDue: true,
+			showRecurring: false,
+			showTimeEntries: false,
+		});
+
+		expect(eventTypes(events)).toEqual(["due", "scheduled"]);
+	});
+
+	it("keeps the due event when scheduled events are hidden", async () => {
+		const task = TaskFactory.createTask({
+			title: "Due only display",
+			path: "Tasks/due-only-display.md",
+			scheduled: "2026-05-31",
+			due: "2026-05-31",
+		});
+
+		const events = await generateCalendarEvents([task], plugin, {
+			showScheduled: false,
+			showDue: true,
+			showRecurring: false,
+			showTimeEntries: false,
+		});
+
+		expect(eventTypes(events)).toEqual(["due"]);
+	});
+
+	it("keeps separate due events when scheduled and due dates differ", async () => {
+		const task = TaskFactory.createTask({
+			title: "Different day task",
+			path: "Tasks/different-day.md",
+			scheduled: "2026-05-31",
+			due: "2026-06-01",
+		});
+
+		const events = await generateCalendarEvents([task], plugin, {
+			showScheduled: true,
+			showDue: true,
+			showRecurring: false,
+			showTimeEntries: false,
+		});
+
+		expect(eventTypes(events)).toEqual(["due", "scheduled"]);
+	});
+});