Fix meta examples (#2379)

This PR fixes a bug in our meta examples.

### Change Type

- [x] `patch` — Bug fix

apps/examples/src/examples/meta-on-change/OnChangeShapeMetaExample.tsx

@@ -1,11 +1,11 @@
-import { Tldraw } from '@tldraw/tldraw'
+import { TLShape, Tldraw, track, useEditor } from '@tldraw/tldraw'
 import '@tldraw/tldraw/tldraw.css'
 
 export default function OnChangeShapeMetaExample() {
 	return (
 		<div className="tldraw__editor">
 			<Tldraw
-				persistenceKey="tldraw_example"
+				persistenceKey="tldraw_change_meta_example"
 				onMount={(editor) => {
 					// See the "meta-on-create" example for more about setting the
 					// initial meta for a shape.
@@ -20,14 +20,33 @@ export default function OnChangeShapeMetaExample() {
 					// all shapes whenever they are updated.
 					editor.sideEffects.registerBeforeChangeHandler('shape', (_prev, next, source) => {
 						if (source !== 'user') return next
-						next.meta = {
-							updatedBy: editor.user.getId(),
-							updatedAt: Date.now(),
+						return {
+							...next,
+							meta: {
+								updatedBy: editor.user.getId(),
+								updatedAt: Date.now(),
+							},
 						}
-						return next
 					})
 				}}
-			/>
+			>
+				<MetaUiHelper />
+			</Tldraw>
 		</div>
 	)
 }
+
+type ShapeWithMyMeta = TLShape & { meta: { updatedBy: string; updatedAt: string } }
+
+export const MetaUiHelper = track(function MetaUiHelper() {
+	const editor = useEditor()
+	const onlySelectedShape = editor.getOnlySelectedShape() as ShapeWithMyMeta | null
+
+	return (
+		<pre style={{ position: 'absolute', zIndex: 300, top: 64, left: 12, margin: 0 }}>
+			{onlySelectedShape
+				? JSON.stringify(onlySelectedShape.meta, null, 2)
+				: 'Select one shape to see its meta data.'}
+		</pre>
+	)
+})

apps/examples/src/examples/meta-on-change/README.md

@@ -7,4 +7,4 @@ Add custom metadata to shapes when they're changed.
 
 ---
 
-In this example, we add updatedAt metadata to shapes when they're updated.
+We can update a shape's metadata whenever it changes. A UI displays the current selected shape's metadata. Create a shape, select it, and move it around. The metadata will updated any time the shape changes.

apps/examples/src/examples/meta-on-create/OnCreateShapeMetaExample.tsx

@@ -1,4 +1,4 @@
-import { Tldraw } from '@tldraw/tldraw'
+import { TLShape, Tldraw, track, useEditor } from '@tldraw/tldraw'
 import '@tldraw/tldraw/tldraw.css'
 
 export default function OnCreateShapeMetaExample() {
@@ -17,7 +17,24 @@ export default function OnCreateShapeMetaExample() {
 						}
 					}
 				}}
-			/>
+			>
+				<MetaUiHelper />
+			</Tldraw>
 		</div>
 	)
 }
+
+type ShapeWithMyMeta = TLShape & { meta: { updatedBy: string; updatedAt: string } }
+
+export const MetaUiHelper = track(function MetaUiHelper() {
+	const editor = useEditor()
+	const onlySelectedShape = editor.getOnlySelectedShape() as ShapeWithMyMeta | null
+
+	return (
+		<pre style={{ position: 'absolute', zIndex: 300, top: 64, left: 12, margin: 0 }}>
+			{onlySelectedShape
+				? JSON.stringify(onlySelectedShape.meta, null, 2)
+				: 'Select one shape to see its meta data.'}
+		</pre>
+	)
+})

apps/examples/src/examples/meta-on-create/README.md

@@ -7,4 +7,4 @@ Add custom metadata to shapes when they're created.
 
 ---
 
-In this example, we add createdBy and createdAt metadata to shapes when they're created.
+We can update a shape's metadata whenever it is created. A UI displays the current selected shape's metadata. Create a shape and select it. The metadata will display its created at / created by data.

apps/examples/src/examples/shape-meta/README.md

@@ -7,4 +7,4 @@ Add a label to shapes with the meta property.
 
 ---
 
-Select a shape and try changing its label. The label is stored in the shape's meta property, which can be used to add custom data to any shape.
+We can update a shape's metadata using a custom UI. Create a shape, select it, and edit the `label` metadata. The label is stored in the shape's meta property, which can be used to add custom data to any shape.

apps/examples/src/examples/shape-meta/ShapeMetaExample.tsx

@@ -26,10 +26,6 @@ export const ShapeLabelUiWithHelper = track(function ShapeLabelUiWithHelper() {
 	const editor = useEditor()
 	const onlySelectedShape = editor.getOnlySelectedShape() as ShapeWithMyMeta | null
 
-	if (!onlySelectedShape) {
-		return null
-	}
-
 	function onChange(e: React.ChangeEvent<HTMLInputElement>) {
 		if (onlySelectedShape) {
 			const { id, type, meta } = onlySelectedShape
@@ -42,7 +38,12 @@ export const ShapeLabelUiWithHelper = track(function ShapeLabelUiWithHelper() {
 
 	return (
 		<div style={{ position: 'absolute', zIndex: 300, top: 64, left: 12 }}>
-			shape label: <input value={onlySelectedShape.meta.label} onChange={onChange} />
+			<pre style={{ margin: '0 0 16px 0' }}>
+				{onlySelectedShape
+					? JSON.stringify(onlySelectedShape.meta, null, 2)
+					: 'Select one shape to see / edit its meta data.'}
+			</pre>
+			{onlySelectedShape && <input value={onlySelectedShape.meta.label} onChange={onChange} />}
 		</div>
 	)
 })

packages/store/src/lib/Store.ts

@@ -382,12 +382,12 @@ export class Store<R extends UnknownRecord = UnknownRecord, Props = unknown> {
 				const recordAtom = (map ?? currentMap)[record.id as IdOf<R>]
 
 				if (recordAtom) {
-					if (beforeUpdate) record = beforeUpdate(recordAtom.get(), record, source)
-
 					// If we already have an atom for this record, update its value.
-
 					const initialValue = recordAtom.__unsafe__getWithoutCapture()
 
+					// If we have a beforeUpdate callback, run it against the initial and next records
+					if (beforeUpdate) record = beforeUpdate(initialValue, record, source)
+
 					// Validate the record
 					record = this.schema.validateRecord(
 						this,
@@ -402,6 +402,7 @@ export class Store<R extends UnknownRecord = UnknownRecord, Props = unknown> {
 					const finalValue = recordAtom.__unsafe__getWithoutCapture()
 
 					// If the value has changed, assign it to updates.
+					// todo: is this always going to be true?
 					if (initialValue !== finalValue) {
 						didChange = true
 						updates[record.id] = [initialValue, finalValue]