[miniflare] Fix KV bulk getWithMetadata dropping metadata for falsy values

.changeset/shaggy-geese-flow.md

@@ -0,0 +1,9 @@
+---
+"miniflare": patch
+---
+
+Fix KV bulk `getWithMetadata` dropping metadata for present-but-falsy values
+
+The bulk-get handler decided whether to wrap an entry as `{ value, metadata }` based on the truthiness of the value rather than on whether the key existed. Keys holding a falsy value — an empty string, or `0`, `false` and `null` when reading with `type: "json"` — were returned as bare values, losing their metadata and diverging from the shape the runtime binding expects for present keys. Empty-string values were the most common trigger.
+
+The check now gates on entry presence, so present keys always keep their `{ value, metadata }` wrapper and only missing keys return a bare `null`.

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

@@ -79,10 +79,14 @@ async function processKeyValue(
 	type: "text" | "json" = "text",
 	withMetadata = false
 ) {
+	// `obj` is `null` only when the key is missing. A present key always has a
+	// `value` stream, so presence — not value truthiness — decides the response
+	// shape: present keys are wrapped as `{ value, metadata }`, missing keys are
+	// returned as a bare `null`.
 	const decoder = new TextDecoder();
 	let decodedValue = "";
-	if (obj?.value) {
-		for await (const chunk of obj?.value) {
+	if (obj !== null) {
+		for await (const chunk of obj.value) {
 			decodedValue += decoder.decode(chunk, { stream: true });
 		}
 		decodedValue += decoder.decode();
@@ -91,22 +95,23 @@ async function processKeyValue(
 	let val = null;
 	const size = decodedValue.length;
 	try {
-		val = !obj?.value
-			? null
-			: type === "json"
-				? JSON.parse(decodedValue)
-				: decodedValue;
+		val =
+			obj === null
+				? null
+				: type === "json"
+					? JSON.parse(decodedValue)
+					: decodedValue;
 	} catch {
 		throw new HttpError(
 			400,
 			`At least one of the requested keys corresponds to a non-${type} value`
 		);
 	}
-	if (val && withMetadata) {
+	if (obj !== null && withMetadata) {
 		return [
 			{
 				value: val,
-				metadata: obj?.metadata ?? null,
+				metadata: obj.metadata ?? null,
 			},
 			size,
 		];

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

@@ -253,6 +253,57 @@ test("bulk get: check metadata as string", async ({ expect }) => {
 	expect(result).toEqual(expectedResult);
 });
 
+test("bulk get: check metadata for empty string value", async ({ expect }) => {
+	const { kv } = ctx;
+	await kv.put("key1", "", { metadata: { testing: true } });
+
+	const result = await kv.getWithMetadata(["key1"]);
+	const expectedResult = new Map([
+		["key1", { value: "", metadata: { testing: true } }],
+	]);
+	expect(result).toEqual(expectedResult);
+});
+
+test("bulk get: check metadata for falsy json values", async ({ expect }) => {
+	const { kv } = ctx;
+	await kv.put("key1", "0", { metadata: { testing: "zero" } });
+	await kv.put("key2", "false", { metadata: { testing: "false" } });
+	await kv.put("key3", "null", { metadata: { testing: "null" } });
+
+	const result = await kv.getWithMetadata(["key1", "key2", "key3"], "json");
+	const expectedResult = new Map([
+		["key1", { value: 0, metadata: { testing: "zero" } }],
+		["key2", { value: false, metadata: { testing: "false" } }],
+		["key3", { value: null, metadata: { testing: "null" } }],
+	]);
+	expect(result).toEqual(expectedResult);
+});
+
+test("bulk get: distinguishes falsy values from missing keys", async ({
+	expect,
+}) => {
+	const { kv } = ctx;
+	await kv.put("key1", "0", { metadata: { testing: true } });
+
+	// A present key holding a falsy value keeps its `{ value, metadata }`
+	// wrapper, while a missing key is still returned as a bare `null`
+	const result = await kv.getWithMetadata(["key1", "key2"], "json");
+	const expectedResult = new Map([
+		["key1", { value: 0, metadata: { testing: true } }],
+		["key2", null],
+	]);
+	expect(result).toEqual(expectedResult);
+});
+
+test("bulk get: returns falsy values without metadata", async ({ expect }) => {
+	const { kv } = ctx;
+	await kv.put("key1", "");
+	await kv.put("key2", "0");
+
+	expect(await kv.get(["key1"])).toEqual(new Map([["key1", ""]]));
+	expect(await kv.get(["key2"], "json")).toEqual(new Map([["key2", 0]]));
+});
+
 test("bulk get: get with metadata for 404", async ({ expect }) => {
 	const { kv } = ctx;