PUT vs PATCH: Full vs Partial Updates¶

Both update a resource, but they make different promises.

PUT — Replace Everything¶

PUT says "here is the complete new state of the resource." Fields you omit are reset to defaults or null.

If the task had a dueDate, a strict PUT clears it because you didn't include it. PUT is idempotent — sending it twice yields the same result.

PATCH — Change Some Fields¶

PATCH says "merge these changes into the existing resource." Omitted fields are left alone.

Only status changes; title and dueDate stay. This is what users usually expect from an "edit" form that submits one field.

Which Should You Build?¶

In practice, PATCH is the workhorse. Most UIs edit a subset of fields. Offer PUT when a client genuinely wants to overwrite the whole object (e.g. a settings document).

Validating Partial Updates¶

With Zod, derive a partial schema so every field becomes optional — but require at least one:

1const PatchTask = CreateTask.partial().refine(
2  (obj) => Object.keys(obj).length > 0,
3  { message: "Provide at least one field to update" },
4);

The Update Handler¶

1export async function PATCH(req, { params }) {
2  const { id } = await params;
3  const session = await requireSession();
4
5  const parsed = PatchTask.safeParse(await req.json());
6  if (!parsed.success) return badRequest(parsed.error);
7
8  // Authorize: only the owner may update
9  const existing = await prisma.task.findUnique({ where: { id } });
10  if (!existing || existing.ownerId !== session.userId) return notFound();
11
12  const task = await prisma.task.update({
13    where: { id },
14    data: parsed.data,           // updatedAt is bumped automatically
15  });
16  return NextResponse.json({ data: task });
17}