fix(form-core): handle string array indices in standard schema error paths (#1689)

* fix(form-core): handle string array indices in prefixSchemaToErrors

- Fix array path handling for Standard Schema validators
- Support both numeric (Zod) and string (Yup) array indices

Fixes #1683

* ci: apply automated fixes and generate docs

* fix(form-core): improve array index path handling in standard schema validator by inspecting form values

* refactor(react-core): simplify path construction in schema validation error handling

* ci: apply automated fixes and generate docs

* Create poor-drinks-heal.md

* ci: apply automated fixes and generate docs

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: LeCarbonator <[email protected]>

Author: 3 people

.changeset/poor-drinks-heal.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/form-core': patch
+---
+
+fix(form-core): handle string array indices in prefixSchemaToErrors

packages/form-core/src/standardSchemaValidator.ts

@@ -19,21 +19,40 @@ export type TStandardSchemaValidatorIssue<
     ? StandardSchemaV1Issue[]
     : never
 
-function prefixSchemaToErrors(issues: readonly StandardSchemaV1Issue[]) {
+function prefixSchemaToErrors(
+  issues: readonly StandardSchemaV1Issue[],
+  formValue: unknown,
+) {
   const schema = new Map<string, StandardSchemaV1Issue[]>()
 
   for (const issue of issues) {
-    const path = [...(issue.path ?? [])]
-      .map((segment) => {
-        const normalizedSegment =
-          typeof segment === 'object' ? segment.key : segment
-        return typeof normalizedSegment === 'number'
-          ? `[${normalizedSegment}]`
-          : normalizedSegment
-      })
-      .join('.')
-      .replace(/\.\[/g, '[')
-
+    const issuePath = issue.path ?? []
+
+    let currentFormValue = formValue
+    let path = ''
+
+    for (let i = 0; i < issuePath.length; i++) {
+      const pathSegment = issuePath[i]
+      if (pathSegment === undefined) continue
+
+      const segment =
+        typeof pathSegment === 'object' ? pathSegment.key : pathSegment
+
+      // Standard Schema doesn't specify if paths should use numbers or stringified numbers for array access.
+      // However, if we follow the path it provides and encounter an array, then we can assume it's intended for array access.
+      const segmentAsNumber = Number(segment)
+      if (Array.isArray(currentFormValue) && !Number.isNaN(segmentAsNumber)) {
+        path += `[${segmentAsNumber}]`
+      } else {
+        path += (i > 0 ? '.' : '') + String(segment)
+      }
+
+      if (typeof currentFormValue === 'object' && currentFormValue !== null) {
+        currentFormValue = currentFormValue[segment as never]
+      } else {
+        currentFormValue = undefined
+      }
+    }
     schema.set(path, (schema.get(path) ?? []).concat(issue))
   }
 
@@ -42,8 +61,9 @@ function prefixSchemaToErrors(issues: readonly StandardSchemaV1Issue[]) {
 
 const transformFormIssues = <TSource extends ValidationSource>(
   issues: readonly StandardSchemaV1Issue[],
+  formValue: unknown,
 ): TStandardSchemaValidatorIssue<TSource> => {
-  const schemaErrors = prefixSchemaToErrors(issues)
+  const schemaErrors = prefixSchemaToErrors(issues, formValue)
   return {
     form: schemaErrors,
     fields: schemaErrors,
@@ -68,7 +88,7 @@ export const standardSchemaValidators = {
 
     if (validationSource === 'field')
       return result.issues as TStandardSchemaValidatorIssue<TSource>
-    return transformFormIssues<TSource>(result.issues)
+    return transformFormIssues<TSource>(result.issues, value)
   },
   async validateAsync<TSource extends ValidationSource>(
     {
@@ -83,7 +103,7 @@ export const standardSchemaValidators = {
 
     if (validationSource === 'field')
       return result.issues as TStandardSchemaValidatorIssue<TSource>
-    return transformFormIssues<TSource>(result.issues)
+    return transformFormIssues<TSource>(result.issues, value)
   },
 }
 

packages/form-core/tests/standardSchemaValidator.spec.ts

@@ -398,4 +398,189 @@ describe('standard schema validator', () => {
   it.todo(
     'Should allow for `disableErrorFlat` to disable flattening `errors` array',
   )
+
+  describe('array path handling', () => {
+    it('should handle numeric array indices correctly', async () => {
+      const form = new FormApi({
+        defaultValues: {
+          people: [{ name: '' }],
+        },
+        validators: {
+          onChange: z.object({
+            people: z.array(
+              z.object({
+                name: z.string().min(1, 'Name is required'),
+              }),
+            ),
+          }),
+        },
+      })
+
+      const field = new FieldApi({
+        form,
+        name: 'people[0].name',
+      })
+
+      field.mount()
+
+      field.setValue('')
+      expect(form.state.errors).toMatchObject([
+        {
+          'people[0].name': [{ message: 'Name is required' }],
+        },
+      ])
+    })
+
+    it('should handle string array indices from standard schema validators', async () => {
+      // Use Zod's superRefine to simulate string paths that some standard schema validators return
+      const schemaWithStringPaths = z
+        .object({
+          people: z.array(
+            z.object({
+              name: z.string(),
+            }),
+          ),
+        })
+        .superRefine((_, ctx) => {
+          ctx.addIssue({
+            code: 'custom',
+            message: 'Name is required',
+            path: ['people', '0', 'name'], // String index to test path handling
+          })
+        })
+
+      const form = new FormApi({
+        defaultValues: {
+          people: [{ name: '' }],
+        },
+        validators: {
+          onChange: schemaWithStringPaths,
+        },
+      })
+
+      const field = new FieldApi({
+        form,
+        name: 'people[0].name',
+      })
+
+      field.mount()
+
+      field.setValue('')
+      expect(form.state.errors).toMatchObject([
+        {
+          'people[0].name': [{ message: 'Name is required' }],
+        },
+      ])
+    })
+
+    it('should handle nested arrays with mixed numeric and string indices', async () => {
+      const form = new FormApi({
+        defaultValues: {
+          users: [
+            {
+              addresses: [
+                { street: 'Main St' },
+                { street: '' }, // This will fail validation
+              ],
+            },
+          ],
+        },
+        validators: {
+          onChange: z.object({
+            users: z.array(
+              z.object({
+                addresses: z.array(
+                  z.object({
+                    street: z.string().min(1, 'Street is required'),
+                  }),
+                ),
+              }),
+            ),
+          }),
+        },
+      })
+
+      const field = new FieldApi({
+        form,
+        name: 'users[0].addresses[1].street',
+      })
+
+      field.mount()
+      field.setValue('')
+
+      expect(form.state.errors).toMatchObject([
+        {
+          'users[0].addresses[1].street': [{ message: 'Street is required' }],
+        },
+      ])
+    })
+
+    it('should handle regular object paths without array indices', async () => {
+      const form = new FormApi({
+        defaultValues: {
+          user: {
+            profile: {
+              name: '',
+            },
+          },
+        },
+        validators: {
+          onChange: z.object({
+            user: z.object({
+              profile: z.object({
+                name: z.string().min(1, 'Name is required'),
+              }),
+            }),
+          }),
+        },
+      })
+
+      const field = new FieldApi({
+        form,
+        name: 'user.profile.name',
+      })
+
+      field.mount()
+
+      field.setValue('')
+      expect(form.state.errors).toMatchObject([
+        {
+          'user.profile.name': [{ message: 'Name is required' }],
+        },
+      ])
+    })
+
+    it('should allow numeric object properties for standard schema issue paths', () => {
+      const form = new FormApi({
+        defaultValues: {
+          foo: {
+            0: { bar: '' },
+          },
+        },
+        validators: {
+          onChange: z.object({
+            foo: z.object({
+              0: z.object({ bar: z.string().email('Must be an email') }),
+            }),
+          }),
+        },
+      })
+      form.mount()
+
+      const field = new FieldApi({
+        form,
+        name: 'foo.0.bar',
+      })
+      field.mount()
+
+      field.setValue('test')
+
+      expect(form.state.errors).toMatchObject([
+        { 'foo.0.bar': [{ message: 'Must be an email' }] },
+      ])
+      expect(field.state.meta.errors).toMatchObject([
+        { message: 'Must be an email' },
+      ])
+    })
+  })
 })