feat(group-array): support default values

CONTRIBUTING.md

@@ -104,7 +104,7 @@ Once you have a `dist` folder being created, you can either:
 + import { createHeadlessForm } from '../../path/to/repo/json-schema-form/dist'
 ```
 
-- Optpion B: Use [npm link](https://docs.npmjs.com/cli/v9/commands/npm-link) or [yarn link](https://classic.yarnpkg.com/lang/en/docs/cli/link/):
+- Option B: Use [npm link](https://docs.npmjs.com/cli/v9/commands/npm-link) or [yarn link](https://classic.yarnpkg.com/lang/en/docs/cli/link/):
 
 ```bash
 # in json-schema-form repo:

src/field/schema.ts

@@ -277,14 +277,17 @@ function getArrayFields(schema: NonBooleanJsfSchema, originalSchema: NonBooleanJ
 
   if (schema.items?.type === 'object') {
     const objectSchema = schema.items as JsfObjectSchema
+    const originalItemsSchema = originalSchema.items as JsfObjectSchema | undefined
 
     for (const key in objectSchema.properties) {
       const isFieldRequired = objectSchema.required?.includes(key) || false
       const field = buildFieldSchema({
         schema: objectSchema.properties[key],
         name: key,
         required: isFieldRequired,
-        originalSchema,
+        // Use the inner field's original schema, not the GROUP_ARRAY schema
+        // This prevents the GROUP_ARRAY's default from being copied to inner fields
+        originalSchema: originalItemsSchema?.properties?.[key] || objectSchema.properties[key],
         strictInputType,
       })
       if (field) {
@@ -298,7 +301,8 @@ function getArrayFields(schema: NonBooleanJsfSchema, originalSchema: NonBooleanJ
       schema: schema.items,
       name: 'item',
       required: false,
-      originalSchema,
+      // Use the items schema from originalSchema, not the GROUP_ARRAY schema itself
+      originalSchema: originalSchema.items || schema.items,
       strictInputType,
     })
     if (field) {
@@ -376,7 +380,7 @@ export function buildFieldSchema({
     const inputType = getInputType(type, name, originalSchema, strictInputType)
     const inputHasInnerFields = ['fieldset', 'group-array'].includes(inputType)
 
-    return {
+    const hiddenField: Field = {
       type: inputType,
       name,
       inputType,
@@ -385,6 +389,13 @@ export function buildFieldSchema({
       isVisible: false,
       ...(inputHasInnerFields && { fields: [] }),
     }
+
+    // Preserve default from originalSchema for hidden fields (important for GROUP_ARRAY fields)
+    if (originalSchema.default !== undefined) {
+      hiddenField.default = originalSchema.default
+    }
+
+    return hiddenField
   }
 
   // If schema is any other boolean (true), just return null
@@ -418,6 +429,12 @@ export function buildFieldSchema({
     ...(errorMessage && { errorMessage }),
   }
 
+  // Preserve default from originalSchema if it's missing in the processed schema
+  // This is important for GROUP_ARRAY fields where defaults can be lost during conditional merging
+  if (field.default === undefined && originalSchema.default !== undefined) {
+    field.default = originalSchema.default
+  }
+
   if (inputType === 'checkbox') {
     addCheckboxAttributes(inputType, field, schema)
   }

test/fields/array.test.ts

@@ -217,8 +217,6 @@ describe('buildFieldArray', () => {
           isVisible: true,
           nameKey: 'title',
           required: false,
-          foo: 'bar',
-          bar: 'baz',
         },
       ],
       items: expect.any(Object),
@@ -1093,4 +1091,245 @@ describe('buildFieldArray', () => {
       // as both will be rendered from the same fields in the `fields` property.
     })
   })
+
+  describe('default values', () => {
+    it('should preserve default values for GROUP_ARRAY fields', () => {
+      const schema: JsfSchema = {
+        type: 'array',
+        default: [
+          { title: 'Book 1', pages: 100 },
+          { title: 'Book 2', pages: 200 },
+        ],
+        items: {
+          type: 'object',
+          properties: {
+            title: { type: 'string' },
+            pages: { type: 'number' },
+          },
+        },
+      }
+
+      const field = buildFieldSchema(schema, 'books', false)
+
+      expect(field?.default).toEqual([
+        { title: 'Book 1', pages: 100 },
+        { title: 'Book 2', pages: 200 },
+      ])
+    })
+
+    it('should preserve default values from originalSchema when processed schema loses it', () => {
+      const originalSchema: JsfSchema = {
+        type: 'array',
+        default: [{ title: 'Test Book', pages: 300 }],
+        items: {
+          type: 'object',
+          properties: {
+            title: { type: 'string' },
+            pages: { type: 'number' },
+          },
+        },
+      }
+
+      // Simulate a processed schema where default was lost (e.g., during conditional merging)
+      const processedSchema: JsfSchema = {
+        type: 'array',
+        // default is missing here
+        items: {
+          type: 'object',
+          properties: {
+            title: { type: 'string' },
+            pages: { type: 'number' },
+          },
+        },
+      }
+
+      const field = buildField({
+        schema: processedSchema,
+        name: 'books',
+        required: false,
+        originalSchema,
+        strictInputType: false,
+      })
+
+      expect(field?.default).toEqual([{ title: 'Test Book', pages: 300 }])
+    })
+
+    it('should use processed schema default if both exist', () => {
+      const originalSchema: JsfSchema = {
+        type: 'array',
+        default: [{ title: 'Original Book', pages: 150 }],
+        items: {
+          type: 'object',
+          properties: {
+            title: { type: 'string' },
+            pages: { type: 'number' },
+          },
+        },
+      }
+
+      const processedSchema: JsfSchema = {
+        type: 'array',
+        default: [{ title: 'Updated Book', pages: 250 }],
+        items: {
+          type: 'object',
+          properties: {
+            title: { type: 'string' },
+            pages: { type: 'number' },
+          },
+        },
+      }
+
+      const field = buildField({
+        schema: processedSchema,
+        name: 'books',
+        required: false,
+        originalSchema,
+        strictInputType: false,
+      })
+
+      // Should use processed schema's default, not originalSchema's
+      expect(field?.default).toEqual([{ title: 'Updated Book', pages: 250 }])
+    })
+
+    it('should preserve default values for GROUP_ARRAY fields that become visible conditionally', () => {
+      const schema: JsfObjectSchema = {
+        type: 'object',
+        properties: {
+          has_books: {
+            type: 'string',
+            default: 'no',
+            oneOf: [
+              { const: 'yes', title: 'Yes' },
+              { const: 'no', title: 'No' },
+            ],
+          },
+          books: {
+            type: 'array',
+            default: [
+              { title: 'Book 1', pages: 100 },
+              { title: 'Book 2', pages: 200 },
+            ],
+            items: {
+              type: 'object',
+              properties: {
+                title: { type: 'string' },
+                pages: { type: 'number' },
+              },
+            },
+          },
+        },
+        allOf: [
+          {
+            if: {
+              properties: {
+                has_books: { const: 'yes' },
+              },
+            },
+            then: {
+              required: ['books'],
+            },
+            else: {
+              properties: {
+                books: false,
+              },
+            },
+          },
+        ],
+      }
+
+      // Initially, field should be hidden but still have default
+      const formInitial = createHeadlessForm(schema, { initialValues: { has_books: 'no' } })
+      const fieldInitial = formInitial.fields.find(f => f.name === 'books')
+      expect(fieldInitial?.isVisible).toBe(false)
+      // Default should be preserved even when hidden
+      expect(fieldInitial?.default).toEqual([
+        { title: 'Book 1', pages: 100 },
+        { title: 'Book 2', pages: 200 },
+      ])
+
+      // When field becomes visible, default should still be available
+      formInitial.handleValidation({ has_books: 'yes' })
+      const fieldVisible = formInitial.fields.find(f => f.name === 'books')
+      expect(fieldVisible?.isVisible).toBe(true)
+      expect(fieldVisible?.default).toEqual([
+        { title: 'Book 1', pages: 100 },
+        { title: 'Book 2', pages: 200 },
+      ])
+    })
+  })
+
+  describe('inner field defaults', () => {
+    it('should NOT copy GROUP_ARRAY default to inner fields', () => {
+      const schema: JsfSchema = {
+        type: 'array',
+        default: [
+          { title: 'Book 1', pages: 100 },
+          { title: 'Book 2', pages: 200 },
+        ],
+        items: {
+          type: 'object',
+          properties: {
+            title: {
+              type: 'string',
+              title: 'Title',
+            },
+            pages: {
+              type: 'number',
+            },
+          },
+        },
+      }
+
+      const field = buildFieldSchema(schema, 'books', false)
+
+      // Parent GROUP_ARRAY field should have the default array
+      expect(field?.default).toEqual([
+        { title: 'Book 1', pages: 100 },
+        { title: 'Book 2', pages: 200 },
+      ])
+
+      // Inner fields should NOT have the parent's default array
+      const titleField = field?.fields?.find(f => f.name === 'title')
+      const pagesField = field?.fields?.find(f => f.name === 'pages')
+
+      expect(titleField?.default).toBeUndefined()
+      expect(pagesField?.default).toBeUndefined()
+    })
+
+    it('should preserve inner field defaults when specified', () => {
+      const schema: JsfSchema = {
+        type: 'array',
+        default: [
+          { title: 'Book 1', pages: 300 },
+        ],
+        items: {
+          type: 'object',
+          properties: {
+            title: {
+              type: 'string',
+              default: 'Untitled',
+            },
+            pages: {
+              type: 'number',
+              default: 0,
+            },
+          },
+        },
+      }
+
+      const field = buildFieldSchema(schema, 'books', false)
+
+      // Parent GROUP_ARRAY field should have the default array
+      expect(field?.default).toEqual([
+        { title: 'Book 1', pages: 300 },
+      ])
+
+      // Inner fields should have their own defaults, not the parent's array
+      const titleField = field?.fields?.find(f => f.name === 'title')
+      const pagesField = field?.fields?.find(f => f.name === 'pages')
+
+      expect(titleField?.default).toBe('Untitled')
+      expect(pagesField?.default).toBe(0)
+    })
+  })
 })