Add Content-Length and FixedLengthStream to R2 get response (#712)

* Add Content-Length and FixedLengthStream to R2 get response

Before this, we would see that the following code wouldn't work:
```
  const res = await env.BUCKET.get(name);
  await env.BUCKET.put(name, res!.body);
```

As it would throw:
	TypeError: Provided readable stream must have a known length (request/response body or readable half of FixedLengthStream)

* Test fixed length R2 get responses

---------

Co-authored-by: bcoll <[email protected]>

Author: gabivlj

packages/miniflare/src/workers/r2/bucket.worker.ts

@@ -184,6 +184,7 @@ function encodeResult(
 		headers: {
 			[R2Headers.METADATA_SIZE]: `${encoded.metadataSize}`,
 			"Content-Type": "application/json",
+			"Content-Length": `${encoded.size}`,
 		},
 	});
 }

packages/miniflare/src/workers/r2/r2Object.worker.ts

@@ -9,6 +9,7 @@ import {
 export interface EncodedMetadata {
 	metadataSize: number;
 	value: ReadableStream<Uint8Array>;
+	size: number;
 }
 
 export class InternalR2Object {
@@ -68,7 +69,7 @@ export class InternalR2Object {
 	encode(): EncodedMetadata {
 		const json = JSON.stringify(this.#rawProperties());
 		const blob = new Blob([json]);
-		return { metadataSize: blob.size, value: blob.stream() };
+		return { metadataSize: blob.size, value: blob.stream(), size: blob.size };
 	}
 
 	static encodeMultiple(objects: InternalR2Objects): EncodedMetadata {
@@ -77,7 +78,7 @@ export class InternalR2Object {
 			objects: objects.objects.map((o) => o.#rawProperties()),
 		});
 		const blob = new Blob([json]);
-		return { metadataSize: blob.size, value: blob.stream() };
+		return { metadataSize: blob.size, value: blob.stream(), size: blob.size };
 	}
 }
 
@@ -92,13 +93,15 @@ export class InternalR2ObjectBody extends InternalR2Object {
 
 	encode(): EncodedMetadata {
 		const { metadataSize, value: metadata } = super.encode();
-		const identity = new IdentityTransformStream();
+		const size = this.range?.length ?? this.size;
+		const identity = new FixedLengthStream(size + metadataSize);
 		void metadata
 			.pipeTo(identity.writable, { preventClose: true })
 			.then(() => this.body.pipeTo(identity.writable));
 		return {
 			metadataSize: metadataSize,
 			value: identity.readable,
+			size,
 		};
 	}
 }

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

@@ -549,6 +549,50 @@ test("put: validates metadata size", async (t) => {
 		expectations
 	);
 });
+test("put: can copy values", async (t) => {
+	const mf = new Miniflare({
+		r2Buckets: ["BUCKET"],
+		modules: true,
+		script: `export default {
+      async fetch(request, env, ctx) {
+        await env.BUCKET.put("key", "0123456789");
+        
+        let object = await env.BUCKET.get("key");
+        await env.BUCKET.put("key-copy", object.body);
+        const copy = await (await env.BUCKET.get("key-copy"))?.text();
+        
+        object = await env.BUCKET.get("key", { range: { offset: 1, length: 4 } });
+        await env.BUCKET.put("key-copy-range-1", object.body);
+        const copyRange1 = await (await env.BUCKET.get("key-copy-range-1"))?.text();
+        
+        object = await env.BUCKET.get("key", { range: { length: 3 } });
+        await env.BUCKET.put("key-copy-range-2", object.body);
+        const copyRange2 = await (await env.BUCKET.get("key-copy-range-2"))?.text();
+        
+        object = await env.BUCKET.get("key", { range: { suffix: 5 } });
+        await env.BUCKET.put("key-copy-range-3", object.body);
+        const copyRange3 = await (await env.BUCKET.get("key-copy-range-3"))?.text();
+        
+        const range = new Headers();
+        range.set("Range", "bytes=0-5");
+        object = await env.BUCKET.get("key", { range });
+        await env.BUCKET.put("key-copy-range-4", object.body);
+        const copyRange4 = await (await env.BUCKET.get("key-copy-range-4"))?.text();
+        
+        return Response.json({ copy, copyRange1, copyRange2, copyRange3, copyRange4 });
+      }
+    }`,
+	});
+	t.teardown(() => mf.dispose());
+	const res = await mf.dispatchFetch("http://localhost");
+	t.deepEqual(await res.json(), {
+		copy: "0123456789",
+		copyRange1: "1234",
+		copyRange2: "012",
+		copyRange3: "56789",
+		copyRange4: "012345",
+	});
+});
 
 test("delete: deletes existing keys", async (t) => {
 	const { r2, ns, object } = t.context;