Fix KVNamespace#put() with empty value

Empty `put()`s may send HTTP requests with `null` bodies, violating
an assumption we had. This change handles this case, and adds some
additional tests for empty values.

Closes #703

Author: mrbbot

packages/miniflare/src/workers/kv/namespace.worker.ts

@@ -128,13 +128,20 @@ export class KVNamespaceObject extends MiniflareDurableObject {
     // through a transform stream to count it (trusting `workerd` to send
     // correct value here).
     let value = req.body;
-    assert(value !== null);
     // Safety of `!`: `parseInt(null)` is `NaN`
     // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
     const contentLength = parseInt(req.headers.get("Content-Length")!);
-    const valueLengthHint = Number.isNaN(contentLength)
-      ? undefined
-      : contentLength;
+    let valueLengthHint: number | undefined;
+    if (!Number.isNaN(contentLength)) valueLengthHint = contentLength;
+    else if (value === null) valueLengthHint = 0;
+
+    // Empty values may be put with `null` bodies:
+    // https://github.com/cloudflare/miniflare/issues/703
+    value ??= new ReadableStream<Uint8Array>({
+      start(controller) {
+        controller.close();
+      },
+    });
 
     const maxValueSize = this.beingTested
       ? KVLimits.MAX_VALUE_SIZE_TEST

packages/miniflare/test/plugins/cache/index.spec.ts

@@ -99,6 +99,18 @@ test("match returns cached responses", async (t) => {
   t.is(res.status, 200);
   t.is(await res.text(), "buffered");
 });
+test("match returns empty response", async (t) => {
+  const cache = t.context.caches.default;
+  const key = "http://localhost/cache-empty";
+  const resToCache = new Response(null, {
+    headers: { "Cache-Control": "max-age=3600" },
+  });
+  await cache.put(key, resToCache);
+  const res = await cache.match(key);
+  assert(res !== undefined);
+  t.is(res.status, 200);
+  t.is(await res.text(), "");
+});
 test("match returns nothing on cache miss", async (t) => {
   const cache = t.context.caches.default;
   const key = "http://localhost/cache-miss";

packages/miniflare/test/plugins/kv/index.spec.ts

@@ -152,6 +152,13 @@ test("put: puts value", async (t) => {
   const results = await kv.list({ prefix: ns });
   t.is(results.keys[0]?.expiration, TIME_FUTURE);
 });
+test("put: puts empty value", async (t) => {
+  // https://github.com/cloudflare/miniflare/issues/703
+  const { kv } = t.context;
+  await kv.put("key", "");
+  const value = await kv.get("key");
+  t.is(value, "");
+});
 test("put: overrides existing keys", async (t) => {
   const { kv } = t.context;
   await kv.put("key", "value1");

packages/miniflare/test/plugins/r2/index.spec.ts

@@ -376,6 +376,14 @@ test("put: returns metadata for created object", async (t) => {
   t.is(object.range, undefined);
   isWithin(t, WITHIN_EPSILON, object.uploaded.getTime(), start);
 });
+test("put: puts empty value", async (t) => {
+  const { r2 } = t.context;
+  const object = await r2.put("key", "");
+  assert(object !== null);
+  t.is(object.size, 0);
+  const objectBody = await r2.get("key");
+  t.is(await objectBody?.text(), "");
+});
 test("put: overrides existing keys", async (t) => {
   const { r2, ns, object } = t.context;
   await r2.put("key", "value1");