fix(arktype-utils): Ensures keys are set on the correct object in an array

.changeset/popular-falcons-fly.md

@@ -0,0 +1,5 @@
+---
+"@jhecht/arktype-utils": patch
+---
+
+Fixes bug not grouping items correctly

packages/arktype-utils/CHANGELOG.md

@@ -19,17 +19,17 @@
   ```ts
   // Test nested objects with dot notation
   const fd = new FormData();
-  fd.append("payments.id1.location", "England");
-  fd.append("payments.id1.age", "37");
-  fd.append("payments.id2.location", "New York");
+  fd.append('payments.id1.location', 'England');
+  fd.append('payments.id1.age', '37');
+  fd.append('payments.id2.location', 'New York');
   const obj = formDataToObject(fd);
 
   // Test nested arrays with bracket notation
   const fd2 = new FormData();
-  fd2.append("locations[].name", "England");
-  fd2.append("locations[].members[]", "John");
-  fd2.append("locations[].members[]", "Joe");
-  fd2.append("locations[].name", "France");
+  fd2.append('locations[].name', 'England');
+  fd2.append('locations[].members[]', 'John');
+  fd2.append('locations[].members[]', 'Joe');
+  fd2.append('locations[].name', 'France');
   const obj2 = formDataToObject(fd2);
   ```
 

packages/arktype-utils/src/formData.test.ts

@@ -118,6 +118,23 @@ describe('formDataToObject', () => {
     const obj = formDataToObject(fd);
     expect(obj.file).toBeInstanceOf(File);
   });
+
+  it('Should work with complex arrays / object combinations', () => {
+    const fd = new FormData();
+    fd.append('bills[].id', 'id1');
+    fd.append('bills[].name', 'Rent');
+    fd.append('bills[].id', 'id2');
+    fd.append('bills[].name', 'Electricity');
+
+    const obj = formDataToObject(fd);
+
+    expect(obj).toStrictEqual({
+      bills: [
+        { id: 'id1', name: 'Rent' },
+        { id: 'id2', name: 'Electricity' },
+      ],
+    });
+  });
 });
 
 describe('formDataToObject - nested keys', () => {

packages/arktype-utils/src/formData.ts

@@ -171,7 +171,11 @@ export function formDataToObject(
   // For grouping array objects by their base path
   const arrayGroups = new Map<
     string,
-    { current: Record<string, unknown>; arr: Record<string, unknown>[] }
+    {
+      current: Record<string, unknown>;
+      arr: Record<string, unknown>[];
+      lastField?: string;
+    }
   >();
   // For collecting repeated simple keys and top-level arrays
   const simpleArrays = new Map<string, unknown[]>();
@@ -191,13 +195,23 @@ export function formDataToObject(
     const arrayIdx = path.findIndex((p) => p === '');
     if (arrayIdx !== -1) {
       const basePath = path.slice(0, arrayIdx).join('.');
-      if (!arrayGroups.has(basePath))
-        arrayGroups.set(basePath, { current: {}, arr: [] });
+      if (!arrayGroups.has(basePath)) {
+        arrayGroups.set(basePath, {
+          current: {},
+          arr: [],
+          lastField: undefined,
+        });
+      }
       const group = arrayGroups.get(basePath)!;
-      // If this is a new object in the array, push current and start new
+      const thisField = String(path[arrayIdx + 1]);
+      // Only push current object when a non-array field repeats
+      const isArrayField =
+        (path.length === arrayIdx + 3 && path[arrayIdx + 2] === '') ||
+        String(path[arrayIdx + 1]).endsWith('[]');
       if (
         Object.keys(group.current).length > 0 &&
-        path[arrayIdx + 1] === 'name'
+        Object.prototype.hasOwnProperty.call(group.current, thisField) &&
+        !isArrayField
       ) {
         group.arr.push(group.current);
         group.current = {};