refactor: switch elements to per-track schemaState

packages/element/src/index.ts

@@ -83,6 +83,7 @@ export * from "./positionElementsOnGrid";
 export * from "./renderElement";
 export * from "./resizeElements";
 export * from "./resizeTest";
+export * from "./schema";
 export * from "./Scene";
 export * from "./selection";
 export * from "./shape";

packages/element/src/mutateElement.ts

@@ -11,6 +11,7 @@ import type { Mutable } from "@excalidraw/common/utility-types";
 import { ShapeCache } from "./shape";
 
 import { updateElbowArrowPoints } from "./elbowArrow";
+import { ensureSchemaStateForElementType } from "./schema";
 
 import { isElbowArrow } from "./typeChecks";
 
@@ -137,6 +138,10 @@ export const mutateElement = <TElement extends Mutable<ExcalidrawElement>>(
   element.version = updates.version ?? element.version + 1;
   element.versionNonce = updates.versionNonce ?? randomInteger();
   element.updated = getUpdatedTimestamp();
+  element.schemaState = ensureSchemaStateForElementType(
+    element.schemaState,
+    element.type,
+  ) as TElement["schemaState"];
 
   return element;
 };
@@ -166,13 +171,21 @@ export const newElementWith = <TElement extends ExcalidrawElement>(
     return element;
   }
 
-  return {
+  const updatedElement = {
     ...element,
     ...updates,
     version: updates.version ?? element.version + 1,
     versionNonce: updates.versionNonce ?? randomInteger(),
     updated: getUpdatedTimestamp(),
   };
+
+  return {
+    ...updatedElement,
+    schemaState: ensureSchemaStateForElementType(
+      updatedElement.schemaState,
+      updatedElement.type,
+    ),
+  };
 };
 
 /**

packages/element/src/newElement.ts

@@ -20,6 +20,7 @@ import {
   getElementAbsoluteCoords,
   getResizedElementAbsoluteCoords,
 } from "./bounds";
+import { ensureSchemaStateForElementType } from "./schema";
 import { newElementWith } from "./mutateElement";
 import { getBoundTextMaxWidth } from "./textElement";
 import { normalizeText, measureText } from "./textMeasurements";
@@ -50,8 +51,6 @@ import type {
   ExcalidrawLineElement,
 } from "./types";
 
-const ELEMENT_SCHEMA_VERSION = 2;
-
 export type ElementConstructorOpts = MarkOptional<
   Omit<ExcalidrawGenericElement, "id" | "type" | "isDeleted" | "updated">,
   | "width"
@@ -72,6 +71,7 @@ export type ElementConstructorOpts = MarkOptional<
   | "roughness"
   | "strokeWidth"
   | "roundness"
+  | "schemaState"
   | "locked"
   | "opacity"
   | "customData"
@@ -146,7 +146,7 @@ const _newElementBase = <T extends ExcalidrawElement>(
     roundness,
     seed: rest.seed ?? randomInteger(),
     version: rest.version || 1,
-    schemaVersion: rest.schemaVersion ?? ELEMENT_SCHEMA_VERSION,
+    schemaState: ensureSchemaStateForElementType(rest.schemaState, type),
     versionNonce: rest.versionNonce ?? 0,
     isDeleted: false as false,
     boundElements,

packages/element/src/schema.ts

@@ -0,0 +1,91 @@
+/**
+ * Shared schema primitives used by element types and higher-level migrations.
+ */
+export const SCHEMA_INITIAL_TRACK_VERSION = 1 as const;
+
+/** Core namespace reserved for built-in Excalidraw migrations. */
+export const SCHEMA_CORE_NAMESPACE = "core" as const;
+export type SchemaNamespace = typeof SCHEMA_CORE_NAMESPACE | `host.${string}`;
+
+/**
+ * A schema track is an independent version line:
+ * - core tracks: "excalidraw.*"
+ * - host tracks: "host.<appId>.<track>"
+ */
+export type SchemaTrack = `excalidraw.${string}` | `host.${string}.${string}`;
+export type ElementSchemaState = Readonly<{
+  tracks: Readonly<Record<string, number>>;
+}>;
+
+/** Core frame track id used by the frame background migration. */
+export const CORE_FRAME_SCHEMA_TRACK = "excalidraw.shape.frame" as const;
+
+/** Latest core track versions supported by this build. */
+export const CORE_SUPPORTED_TRACKS = {
+  [CORE_FRAME_SCHEMA_TRACK]: 2,
+} as const;
+
+const getRequiredCoreTracksForElementType = (type: string) => {
+  if (type === "frame") {
+    return {
+      [CORE_FRAME_SCHEMA_TRACK]: CORE_SUPPORTED_TRACKS[CORE_FRAME_SCHEMA_TRACK],
+    } as const;
+  }
+
+  return {} as const;
+};
+
+const isValidTrackVersion = (version: unknown): version is number =>
+  typeof version === "number" &&
+  Number.isInteger(version) &&
+  version >= SCHEMA_INITIAL_TRACK_VERSION;
+
+/**
+ * Ensures an element schema state is normalized and satisfies type defaults.
+ * Required core tracks are only ever bumped forward (never downgraded).
+ */
+export const ensureSchemaStateForElementType = (
+  schemaState: ElementSchemaState | undefined,
+  type: string,
+): ElementSchemaState => {
+  const requiredTracks = getRequiredCoreTracksForElementType(type);
+  const currentTracks = schemaState?.tracks || {};
+  const nextTracks: Record<string, number> = {};
+  let didChange = !schemaState;
+
+  for (const [track, version] of Object.entries(
+    currentTracks as Record<string, unknown>,
+  )) {
+    if (isValidTrackVersion(version)) {
+      nextTracks[track] = version;
+      continue;
+    }
+    nextTracks[track] = SCHEMA_INITIAL_TRACK_VERSION;
+    didChange = true;
+  }
+
+  for (const [track, requiredVersion] of Object.entries(requiredTracks)) {
+    const currentVersion = nextTracks[track];
+    if (
+      !isValidTrackVersion(currentVersion) ||
+      currentVersion < requiredVersion
+    ) {
+      nextTracks[track] = requiredVersion;
+      didChange = true;
+    }
+  }
+
+  if (!didChange) {
+    return schemaState!;
+  }
+
+  return { tracks: nextTracks };
+};
+
+/**
+ * Default schema state for newly created elements.
+ * New frames are created at the latest supported frame track version.
+ */
+export const getDefaultSchemaStateForElementType = (
+  type: string,
+): ElementSchemaState => ensureSchemaStateForElementType(undefined, type);

packages/element/src/types.ts

@@ -15,6 +15,8 @@ import type {
   ValueOf,
 } from "@excalidraw/common/utility-types";
 
+import type { ElementSchemaState } from "./schema";
+
 export type ChartType = "bar" | "line";
 export type FillStyle = "hachure" | "cross-hatch" | "solid" | "zigzag";
 export type FontFamilyKeys = keyof typeof FONT_FAMILY;
@@ -58,8 +60,8 @@ type _ExcalidrawElementBase = Readonly<{
   /** Integer that is sequentially incremented on each change. Used to reconcile
       elements during collaboration or when saving to server. */
   version: number;
-  /** Schema version hint used for per-element migration on restore. */
-  schemaVersion?: number;
+  /** Per-track schema state used by migrations during restore. */
+  schemaState: ElementSchemaState;
   /** Random integer that is regenerated on each change.
       Used for deterministic reconciliation of updates during collaboration,
       in case the versions (see above) are identical. */