[core] Port fix for getArrayDefaults

Author: x0k

.changeset/cuddly-shoes-lick.md

@@ -0,0 +1,7 @@
+---
+"@sjsf/form": patch
+---
+
+Port fix for `getArrayDefaults`
+
+- [Bug: Issue with array schema defaults not applying properly when formData is an empty array](https://github.com/rjsf-team/react-jsonschema-form/pull/4359)

packages/form/CHANGELOG.md

@@ -62,7 +62,7 @@
 
 ### Patch Changes
 
-- [`23f37ab`](https://github.com/x0k/svelte-jsonschema-form/commit/23f37abf7b928bfef45a45ab4a902660a139bfcd) Thanks [@x0k](https://github.com/x0k)! - Porst a bunch of fixes for `getDefaultFormState`:
+- [`23f37ab`](https://github.com/x0k/svelte-jsonschema-form/commit/23f37abf7b928bfef45a45ab4a902660a139bfcd) Thanks [@x0k](https://github.com/x0k)! - Port a bunch of fixes for `getDefaultFormState`:
 
   - [Bug: issue with dependencies computeDefaults](https://github.com/rjsf-team/react-jsonschema-form/pull/4282)
   - [Make fields with const pre-fiiled and readonly](https://github.com/rjsf-team/react-jsonschema-form/pull/4326)

packages/form/src/core/default-state.test.ts

@@ -637,6 +637,51 @@ describe("getDefaultFormState2()", () => {
         },
       });
     });
+    it("test an array with defaults with no formData", () => {
+      const schema: Schema = {
+        type: "array",
+        minItems: 4,
+        default: ["Raphael", "Michaelangelo"],
+        items: {
+          type: "string",
+          default: "Unknown",
+        },
+      };
+
+      expect(
+        computeDefaults3(testValidator, defaultMerger, schema, {
+          ...defaults,
+          rootSchema: schema,
+          includeUndefinedValues: "excludeObjectChildren",
+        })
+      ).toEqual(["Raphael", "Michaelangelo", "Unknown", "Unknown"]);
+    });
+    it("test an array with defaults with empty array as formData", () => {
+      const schema: Schema = {
+        type: "array",
+        minItems: 4,
+        default: ["Raphael", "Michaelangelo"],
+        items: {
+          type: "string",
+          default: "Unknown",
+        },
+      };
+
+      expect(
+        computeDefaults3(testValidator, defaultMerger, schema, {
+          ...defaults,
+          rootSchema: schema,
+          rawFormData: [],
+          includeUndefinedValues: "excludeObjectChildren",
+          experimental_defaultFormStateBehavior: {
+            arrayMinItems: {
+              mergeExtraDefaults: true,
+              populate: "all",
+            },
+          },
+        })
+      ).toEqual(["Raphael", "Michaelangelo", "Unknown", "Unknown"]);
+    });
     it("test computeDefaults handles an invalid property schema", () => {
       const schema: Schema = {
         type: "object",

packages/form/src/core/default-state.ts

@@ -670,17 +670,20 @@ export function getArrayDefaults(
   }: ComputeDefaultsProps2,
   defaults: SchemaArrayValue | undefined
 ): SchemaArrayValue | undefined {
-  const neverPopulate =
-    experimental_defaultFormStateBehavior?.arrayMinItems?.populate === "never";
-  const ignoreMinItemsFlagSet =
-    experimental_defaultFormStateBehavior?.arrayMinItems?.populate ===
-    "requiredOnly";
+  const {
+    populate: arrayMinItemsPopulate,
+    mergeExtraDefaults: arrayMergeExtraDefaults,
+    computeSkipPopulate = () => false,
+  } = experimental_defaultFormStateBehavior?.arrayMinItems ?? {};
+
+  const neverPopulate = arrayMinItemsPopulate === "never";
+  const ignoreMinItemsFlagSet = arrayMinItemsPopulate === "requiredOnly";
+  const isPopulateAll =
+    arrayMinItemsPopulate === "all" ||
+    (!neverPopulate && !ignoreMinItemsFlagSet);
   const isSkipEmptyDefaults =
     experimental_defaultFormStateBehavior?.emptyObjectFields ===
     "skipEmptyDefaults";
-  const computeSkipPopulate =
-    experimental_defaultFormStateBehavior?.arrayMinItems?.computeSkipPopulate ??
-    (() => false);
 
   const emptyDefault: SchemaArrayValue | undefined = isSkipEmptyDefaults
     ? undefined
@@ -713,7 +716,7 @@ export function getArrayDefaults(
     if (neverPopulate) {
       defaults = rawFormData;
     } else {
-      defaults = rawFormData.map((item, idx) => {
+      const itemDefaults = rawFormData.map((item, idx) => {
         return computeDefaults3(validator, merger, schemaItem, {
           rootSchema,
           stack,
@@ -725,6 +728,16 @@ export function getArrayDefaults(
           isSchemaRoot: false,
         });
       });
+      // If the populate 'requiredOnly' flag is set then we only merge and include extra defaults if they are required.
+      // Or if populate 'all' is set we merge and include extra defaults.
+      const mergeExtraDefaults =
+        ((ignoreMinItemsFlagSet && required) || isPopulateAll) &&
+        arrayMergeExtraDefaults === true;
+      defaults = mergeDefaultsWithFormData(
+        defaults,
+        itemDefaults,
+        mergeExtraDefaults
+      );
     }
   }