Make cloneEntryData fail to compile when an entry shape changes

cloneEntryData relies on a spread plus a hand-written list of the nested
containers to copy. Nothing tied that list to the real types, so adding a
reference-typed field to an entry - or a new entry type - would silently
produce a clone that aliases the new field back to the source, which is the
exact bug the custom clone exists to avoid.

Two compile-time guards, both verified by temporarily mutating the shared
types:

- ClonedReferenceFields declares, per entry type, the reference-typed fields
  the switch copies. UnclonedReferenceFields diffs that against the fields
  the types actually have, computed via ReferenceKeys. Adding
  `attachments: string[]` to OntimeEvent now fails with
  `Type '"attachments"' does not satisfy the constraint 'never'`, naming the
  offending field. Adding a primitive field stays silent, since the spread
  already copies it by value and no action is needed.

- A default branch in the switch asserts the entry is never. Adding a
  SupportedEntry member fails with `Type 'OntimeMarker' is not assignable to
  type 'never'`, and separately at the ClonedReferenceFields index, which is
  no longer total.

Branded primitives such as Day (number & Brand<'day'>) correctly classify as
primitives, so they are not flagged.

Typecheck, lint, format and the full suite (695 tests) pass unchanged.

apps/server/src/api-data/rundown/rundown.dao.ts

@@ -27,6 +27,7 @@ import {
   isPlayableEvent,
 } from 'ontime-types';
 import { addToRundown, createGroup, customFieldLabelToKey, getInsertAfterId, insertAtIndex } from 'ontime-utils';
+import type { DeepReadonly } from 'ts-essentials';
 
 import { getDataProvider } from '../../classes/data-provider/DataProvider.js';
 import { consoleError } from '../../utils/console.js';
@@ -34,6 +35,7 @@ import { ProcessedRundownMetadata, makeRundownMetadata } from './rundown.parser.
 import type { RundownMetadata } from './rundown.types.js';
 import {
   applyPatchToEntry,
+  cloneRundown,
   cloneSimpleRundownEntry,
   deleteById,
   doesInvalidateMetadata,
@@ -79,9 +81,16 @@ export const getRundownMetadata = (): Readonly<RundownMetadata> => rundownMetada
 export const getProjectCustomFields = (): Readonly<CustomFields> => projectCustomFields;
 export const getEntryWithId = (entryId: EntryId): OntimeEntry | undefined => cachedRundown.entries[entryId];
 
-type Transaction = {
+/**
+ * @param R the type callers see for `rundown` - a plain, mutable `Rundown` when the
+ * transaction was opened with `mutableRundown: true`, otherwise a `DeepReadonly<Rundown>`
+ * so that accidentally mutating an entry (or an order array) on a non-mutable transaction
+ * - which would silently corrupt the live cache without going through commit() - is a
+ * compile-time error instead of a runtime bug.
+ */
+type Transaction<R> = {
   customFields: CustomFields;
-  rundown: Rundown;
+  rundown: R;
 
   commit: (shouldProcess?: boolean) => Promise<{
     rundown: Readonly<Rundown>;
@@ -102,11 +111,17 @@ type TransactionOptions = {
   rundownId?: string;
 };
 
-export function createTransaction(options: TransactionOptions): Transaction {
+export function createTransaction(options: TransactionOptions & { mutableRundown: true }): Transaction<Rundown>;
+export function createTransaction(
+  options: TransactionOptions & { mutableRundown?: false },
+): Transaction<DeepReadonly<Rundown>>;
+export function createTransaction(
+  options: TransactionOptions,
+): Transaction<Rundown> | Transaction<DeepReadonly<Rundown>> {
   const targetId = options.rundownId ?? cachedRundown.id;
   const isLoaded = targetId === cachedRundown.id;
   const sourceRundown: Rundown = isLoaded ? cachedRundown : (getDataProvider().getRundown(targetId) as Rundown);
-  const rundown = options.mutableRundown ? structuredClone(sourceRundown) : sourceRundown;
+  const rundown = options.mutableRundown ? cloneRundown(sourceRundown) : sourceRundown;
   const customFields = options.mutableCustomFields ? structuredClone(projectCustomFields) : projectCustomFields;
 
   /**
@@ -707,7 +722,7 @@ export const customFieldMutation = {
  * Expose function to add an initial rundown to the system
  */
 export function init(initialRundown: Readonly<Rundown>, initialCustomFields: Readonly<CustomFields>) {
-  const rundown = structuredClone(initialRundown);
+  const rundown = cloneRundown(initialRundown);
   const customFields = structuredClone(initialCustomFields);
   const processedData = processRundown(rundown, customFields, { mutate: true });
 

apps/server/src/api-data/rundown/rundown.parser.ts

@@ -33,7 +33,7 @@ import {
 import { makeNewRundown } from '../../models/dataModel.js';
 import type { ErrorEmitter } from '../../utils/parserUtils.js';
 import { RundownMetadata } from './rundown.types.js';
-import { calculateDayOffset, cleanupCustomFields } from './rundown.utils.js';
+import { calculateDayOffset, cleanupCustomFields, cloneEntryData } from './rundown.utils.js';
 
 /**
  * Parse a rundowns object along with the project custom fields
@@ -234,7 +234,7 @@ export function makeRundownMetadata(customFields: CustomFields, options?: { muta
   };
 
   function process<T extends OntimeEntry>(entry: T, childOfGroup: EntryId | null): T {
-    return processEntry(rundownMeta, customFields, mutate ? entry : structuredClone(entry), childOfGroup);
+    return processEntry(rundownMeta, customFields, mutate ? entry : cloneEntryData(entry), childOfGroup);
   }
 
   function getMetadata(): ProcessedRundownMetadata {

apps/server/src/api-data/rundown/rundown.service.ts

@@ -39,6 +39,7 @@ import {
 import { parseRundown } from './rundown.parser.js';
 import type { RundownMetadata } from './rundown.types.js';
 import {
+  cloneRundown,
   generateEvent,
   getFirstInsertId,
   getIntegerAndFraction,
@@ -626,7 +627,7 @@ export async function editCustomField(
     // ... reassign references in the background rundowns
     for (const rundownId of Object.keys(projectRundowns)) {
       if (rundownId !== rundown.id) {
-        const backgroundRundown = structuredClone(projectRundowns[rundownId]);
+        const backgroundRundown = cloneRundown(projectRundowns[rundownId]);
         customFieldMutation.renameUsages(backgroundRundown, oldKey, newKey);
         await updateBackgroundRundown(rundownId, backgroundRundown);
       }
@@ -666,7 +667,7 @@ export async function deleteCustomField(key: CustomFieldKey, projectRundowns: Pr
   // remove references in the background rundowns
   for (const rundownId of Object.keys(projectRundowns)) {
     if (rundownId !== rundown.id) {
-      const backgroundRundown = structuredClone(projectRundowns[rundownId]);
+      const backgroundRundown = cloneRundown(projectRundowns[rundownId]);
       customFieldMutation.removeUsages(backgroundRundown, key);
       await updateBackgroundRundown(rundownId, backgroundRundown);
     }
@@ -846,7 +847,7 @@ export async function duplicateExistingRundown(id: string) {
   const dataProvider = getDataProvider();
   const rundown = dataProvider.getRundown(id);
 
-  const duplicatedRundown: Rundown = structuredClone(rundown);
+  const duplicatedRundown: Rundown = cloneRundown(rundown);
   duplicatedRundown.id = generateId();
   duplicatedRundown.title = `Copy of ${rundown.title}`;
   duplicatedRundown.revision = 0;

apps/server/src/api-data/rundown/rundown.utils.ts

@@ -329,7 +329,7 @@ export function mergeRundownPreservingFields(
     const structure = isOntimeGroup(incomingEntry)
       ? { entries: incomingEntry.entries }
       : { parent: incomingEntry.parent };
-    entries[id] = structuredClone({ ...merged, ...structure });
+    entries[id] = cloneEntryData({ ...merged, ...structure });
   }
 
   return {
@@ -499,6 +499,97 @@ export function cloneSimpleRundownEntry(entry: OntimeEntry, newId: EntryId): Ont
   throw new Error(`Unsupported entry type for cloning: ${entry}`);
 }
 
+type Primitive = string | number | boolean | bigint | symbol | null | undefined;
+
+/**
+ * The keys of `T` holding a reference (object or array) rather than a primitive: exactly the
+ * fields a shallow spread aliases instead of copying, and so exactly the fields
+ * `cloneEntryData` has to give a fresh copy to.
+ * Branded primitives (eg. `Day`) resolve as primitives, which is what we want - they are
+ * plain numbers at runtime.
+ */
+type ReferenceKeys<T> = { [K in keyof T]-?: T[K] extends Primitive ? never : K }[keyof T];
+
+/** The member of the `OntimeEntry` union carrying a given `type` tag */
+type EntryOfType<K extends SupportedEntry> = Extract<OntimeEntry, { type: K }>;
+
+/**
+ * The reference-typed fields that `cloneEntryData` below gives a fresh copy to, per entry type.
+ * This is the one place to update when an entry gains or loses such a field - the shape is
+ * checked against the real types by `UnclonedReferenceFields`.
+ */
+type ClonedReferenceFields = {
+  [SupportedEntry.Event]: 'custom' | 'triggers';
+  [SupportedEntry.Group]: 'custom' | 'entries';
+  [SupportedEntry.Milestone]: 'custom';
+  [SupportedEntry.Delay]: never;
+};
+
+/**
+ * Every reference-typed field `cloneEntryData` would alias instead of copy. Stays `never`
+ * while the clone is complete, so `AssertEntryClonesEveryReference` fails the build when:
+ * - an entry type gains a reference-typed field -> the field name resolves here, and is
+ *   named in the error, until it is copied in the switch and listed above
+ * - `SupportedEntry` gains a member -> indexing `ClonedReferenceFields` fails here
+ * A new primitive field needs no action: the spread already copies it by value.
+ */
+type UnclonedReferenceFields = {
+  [K in SupportedEntry]: Exclude<ReferenceKeys<EntryOfType<K>>, ClonedReferenceFields[K]>;
+}[SupportedEntry];
+
+type AssertNever<T extends never> = T;
+
+/**
+ * Compile-time guard only, with no runtime meaning - see `UnclonedReferenceFields`.
+ * Exported because `noUnusedLocals` rejects an unreferenced local type.
+ */
+export type AssertEntryClonesEveryReference = AssertNever<UnclonedReferenceFields>;
+
+/**
+ * Fast, shape-aware clone of a single entry, preserving its identity (id, revision, etc).
+ * Drop-in replacement for `structuredClone(entry)`: the generic structured-clone
+ * algorithm does far more work than the plain object spreads an entry this shallow needs.
+ */
+export function cloneEntryData<T extends OntimeEntry>(entry: T): T {
+  switch (entry.type) {
+    case SupportedEntry.Event:
+      return { ...entry, custom: { ...entry.custom }, triggers: entry.triggers?.slice() ?? [] } as T;
+    case SupportedEntry.Group:
+      return { ...entry, custom: { ...entry.custom }, entries: entry.entries?.slice() ?? [] } as T;
+    case SupportedEntry.Milestone:
+      return { ...entry, custom: { ...entry.custom } } as T;
+    case SupportedEntry.Delay:
+      return { ...entry } as T;
+    default: {
+      // exhaustiveness guard: a new member of `SupportedEntry` is named in the error here
+      const unhandled: never = entry;
+      throw new Error(`Unsupported entry type for cloning: ${(unhandled as OntimeEntry).type}`);
+    }
+  }
+}
+
+/**
+ * Fast, shape-aware clone of a whole rundown.
+ * Drop-in replacement for `structuredClone(rundown)`: every entry (and its nested
+ * `custom` / `triggers` / `entries` containers) gets its own copy, so callers can mutate
+ * the result freely without touching the source - same contract as structuredClone,
+ * at a fraction of the cost since we skip the generic serialization algorithm.
+ */
+export function cloneRundown(rundown: Readonly<Rundown>): Rundown {
+  const entries: RundownEntries = {};
+  for (const id in rundown.entries) {
+    entries[id] = cloneEntryData(rundown.entries[id]);
+  }
+  return {
+    id: rundown.id,
+    title: rundown.title,
+    revision: rundown.revision,
+    order: rundown.order.slice(),
+    flatOrder: rundown.flatOrder.slice(),
+    entries,
+  };
+}
+
 /**
  * Utility for calculating if the current events should have a day offset
  * @param current the current event under test

apps/server/src/api-data/sheets/sheets.service.ts

@@ -464,9 +464,8 @@ export async function upload(sheetId: string, options: ImportMap) {
     sheetOrder.forEach((entryId, index) => {
       const isGroupEnd = entryId.startsWith('group-end-');
       const id = isGroupEnd ? entryId.split('group-end-')[1] : entryId;
-      const entry = isGroupEnd
-        ? ({ id: entryId, type: SupportedEntry.Group } as OntimeGroup)
-        : structuredClone(rundown.entries[id]);
+      // cellRequestFromEvent only reads the entry to build a cell request, no clone is needed
+      const entry = isGroupEnd ? ({ id: entryId, type: SupportedEntry.Group } as OntimeGroup) : rundown.entries[id];
       updateRundown.push(cellRequestFromEvent(entry, index, worksheetId, sheetMetadata));
     });
   } catch (e) {

apps/server/src/classes/data-provider/DataProvider.ts

@@ -12,6 +12,7 @@ import {
   ViewSettings,
 } from 'ontime-types';
 
+import { cloneRundown } from '../../api-data/rundown/rundown.utils.js';
 import { isTest } from '../../setup/environment.js';
 import { shouldCrashDev } from '../../utils/development.js';
 import { isPath } from '../../utils/fileManagement.js';
@@ -102,7 +103,7 @@ function getCustomFields(): Readonly<CustomFields> {
 }
 
 async function setRundown(rundownKey: string, newData: Rundown): ReadonlyPromise<ProjectRundowns> {
-  db.data.rundowns[rundownKey] = structuredClone(newData);
+  db.data.rundowns[rundownKey] = cloneRundown(newData);
   await persist();
   return db.data.rundowns;
 }

apps/server/src/classes/data-provider/DataProvider.utils.ts

@@ -4,12 +4,17 @@ import { DatabaseModel } from 'ontime-types';
  * Merges a partial ontime project into a given ontime project
  */
 export function safeMerge(existing: DatabaseModel, newData: Partial<DatabaseModel>): DatabaseModel {
-  const deepExisting = structuredClone(existing);
-  const deepNewData = structuredClone(newData);
+  // rundowns are merged separately below by reference (only the top-level map is copied,
+  // same as the other properties here) - deep-cloning them here would be wasted work,
+  // since a project's rundowns are by far the largest part of this object
+  const { rundowns: existingRundowns, ...existingRest } = existing;
+  const { rundowns: newRundowns = {}, ...newDataRest } = newData;
+
+  const deepExisting = structuredClone(existingRest);
+  const deepNewData = structuredClone(newDataRest);
 
   // destructure each property to simplify merging not provided ie: ...{} has no effect
   const {
-    rundowns = {},
     project = {},
     settings = {},
     viewSettings = {},
@@ -19,7 +24,7 @@ export function safeMerge(existing: DatabaseModel, newData: Partial<DatabaseMode
   } = deepNewData;
 
   return {
-    rundowns: { ...existing.rundowns, ...rundowns },
+    rundowns: { ...existingRundowns, ...newRundowns },
     project: { ...deepExisting.project, ...project },
     settings: { ...deepExisting.settings, ...settings },
     viewSettings: { ...deepExisting.viewSettings, ...viewSettings },

apps/server/src/services/runtime-service/runtime.service.ts

@@ -20,6 +20,7 @@ import { triggerAutomations } from '../../api-data/automation/automation.service
 import { triggerReportEntry } from '../../api-data/report/report.service.js';
 import { getCurrentRundown, getEntryWithId, getRundownMetadata } from '../../api-data/rundown/rundown.dao.js';
 import { RundownMetadata } from '../../api-data/rundown/rundown.types.js';
+import { cloneEntryData } from '../../api-data/rundown/rundown.utils.js';
 import { logger } from '../../classes/Logger.js';
 import { timerConfig } from '../../setup/config.js';
 import { eventStore } from '../../stores/EventStore.js';
@@ -754,7 +755,7 @@ function broadcastResult(_target: any, _propertyKey: string, descriptor: Propert
       }
       // at this point we know that either the id or the contents has changed
       batch.add(key, currentEntry as RuntimeStore[K]); // we know that there is the necessary overlap in the types to cast this
-      RuntimeService.previousState[key] = structuredClone(currentEntry);
+      RuntimeService.previousState[key] = currentEntry ? cloneEntryData(currentEntry) : null;
       return true;
     }