perf(form-core): extract meta markers to state object (v2)

.changeset/easy-rice-live.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/form-core': patch
+---
+
+Improve field snapshot and metadata re-use strategy.

packages/form-core/src/FieldApi/FieldApi.lib.ts

@@ -61,6 +61,7 @@ import type {
 } from '../validation.public'
 import type {
   ChildContributionStates,
+  DerivedMetaMarkers,
   FieldAtoms,
   InternalBaseFieldMeta,
   InternalFieldMeta,
@@ -348,11 +349,21 @@ export class InternalFieldApi<
       metaAtom = createAtom(defaultInternalBaseFieldMeta)
     }
     if (!storeAtom) {
+      const markers: DerivedMetaMarkers = {
+        source: undefined,
+        canDisplayErrors: undefined,
+      }
       storeAtom = createAtom<InternalFieldState>((prev) => {
         const newMeta = metaAtom.get()
         const value = this._getValue()
 
-        const meta = deriveFromBaseFieldMeta(newMeta, prev?.meta, this, value)
+        const meta = deriveFromBaseFieldMeta(
+          newMeta,
+          prev?.meta,
+          this,
+          value,
+          markers,
+        )
 
         if (prev?.meta === meta && prev.value === value) {
           return prev

packages/form-core/src/FieldApi/fieldState.lib.ts

@@ -49,14 +49,13 @@ export interface FormGroupFieldErrorMeta {
 export interface InternalBaseFieldMeta extends BaseFieldMeta, MetaExtension {}
 export interface InternalFieldMeta extends AnyPublicFieldMeta, MetaExtension {}
 
-const derivedMetaSourceKey = Symbol('tanstack-form-derived-meta-source')
-const derivedMetaCanDisplayErrorsKey = Symbol(
-  'tanstack-form-derived-meta-can-display-errors',
-)
-
-type DerivedMetaMarkers = {
-  [derivedMetaCanDisplayErrorsKey]?: boolean
-  [derivedMetaSourceKey]?: InternalBaseFieldMeta
+/**
+ * @private
+ * Used to track the prev meta for a field
+ */
+export interface DerivedMetaMarkers {
+  source: InternalBaseFieldMeta | undefined
+  canDisplayErrors: boolean | undefined
 }
 
 export interface InternalFieldState extends PublicFieldState<any, any> {
@@ -118,6 +117,7 @@ export function deriveFromBaseFieldMeta(
   previousMeta: InternalFieldMeta | undefined,
   field: AnyInternalFieldApi | undefined,
   value?: any,
+  markers?: DerivedMetaMarkers,
 ): InternalFieldMeta {
   const isDefaultValue = field ? field._getIsDefaultValue(value) : true
   const errorVisibility = getErrorVisibility(field)
@@ -152,10 +152,12 @@ export function deriveFromBaseFieldMeta(
 
   if (
     previousMeta &&
+    markers &&
     canReusePreviousMeta({
       baseMeta,
       canDisplayErrors,
       isDefaultValue,
+      markers,
       originalErrors,
       previousMeta,
     })
@@ -184,55 +186,32 @@ export function deriveFromBaseFieldMeta(
     subfields,
     isPristine: !isDirty,
   }
-  return markDerivedMeta(result, baseMeta, canDisplayErrors)
-}
 
-function markDerivedMeta(
-  meta: InternalFieldMeta,
-  baseMeta: InternalBaseFieldMeta,
-  canDisplayErrors: boolean,
-): InternalFieldMeta {
-  Object.defineProperties(meta, {
-    [derivedMetaCanDisplayErrorsKey]: {
-      value: canDisplayErrors,
-    },
-    [derivedMetaSourceKey]: {
-      value: baseMeta,
-    },
-  })
-
-  return meta
-}
-
-function getDerivedMetaSource(
-  meta: (InternalFieldMeta & DerivedMetaMarkers) | undefined,
-): InternalBaseFieldMeta | undefined {
-  return meta?.[derivedMetaSourceKey]
-}
+  if (markers) {
+    markers.source = baseMeta
+    markers.canDisplayErrors = canDisplayErrors
+  }
 
-function getDerivedMetaCanDisplayErrors(
-  meta: (InternalFieldMeta & DerivedMetaMarkers) | undefined,
-): boolean | undefined {
-  return meta?.[derivedMetaCanDisplayErrorsKey]
+  return result
 }
 
 function canReusePreviousMeta({
   baseMeta,
   canDisplayErrors,
   isDefaultValue,
+  markers,
   originalErrors,
   previousMeta,
 }: {
   baseMeta: InternalBaseFieldMeta
   canDisplayErrors: boolean
   isDefaultValue: boolean
+  markers: DerivedMetaMarkers
   originalErrors: Array<ValidationIssue>
   previousMeta: InternalFieldMeta
 }): boolean {
-  if (getDerivedMetaSource(previousMeta) !== baseMeta) return false
-  if (getDerivedMetaCanDisplayErrors(previousMeta) !== canDisplayErrors) {
-    return false
-  }
+  if (markers.source !== baseMeta) return false
+  if (markers.canDisplayErrors !== canDisplayErrors) return false
   if (previousMeta.isDefaultValue !== isDefaultValue) return false
   if (previousMeta.original.errors !== originalErrors) return false
 

packages/form-core/src/utils.lib.ts

@@ -29,30 +29,27 @@ export function nameToFieldNodeSegments(
   if (typeof nameOrSegments !== 'string') return nameOrSegments.slice()
 
   const result: NameSegments = []
-  let s = ''
+  let start = 0
 
   for (let i = 0; i < nameOrSegments.length; i++) {
     switch (nameOrSegments.charCodeAt(i)) {
       case 0x2e: // '.'
       case 0x5b: // '['
-        if (s.length > 0) {
-          result.push(s)
-          s = ''
+        if (i > start) {
+          result.push(nameOrSegments.slice(start, i))
         }
+        start = i + 1
         break
       case 0x5d: // ']'
-        if (s.length > 0) {
-          result.push(parseInt(s, 10))
-          s = ''
+        if (i > start) {
+          result.push(parseInt(nameOrSegments.slice(start, i), 10))
         }
-        break
-      default:
-        s += nameOrSegments.charAt(i)
+        start = i + 1
         break
     }
   }
-  if (s.length > 0) {
-    result.push(s)
+  if (start < nameOrSegments.length) {
+    result.push(nameOrSegments.slice(start))
   }
 
   return result