lib: allow byob reader for 'blob.stream()'

Fixes: #47993 PR-URL: #49713 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

Author: debadree25

lib/internal/blob.js

@@ -321,6 +321,7 @@ class Blob{
 
 constreader=this[kHandle].getReader();
 returnnewlazyReadableStream({
+type: 'bytes',
 start(c){
 // There really should only be one read at a time so using an
 // array here is purely defensive.
@@ -340,6 +341,9 @@ class Blob{
 if(status===0){
 // EOS
 c.close();
+// This is to signal the end for byob readers
+// see https://streams.spec.whatwg.org/#example-rbs-pull
+c.byobRequest?.respond(0);
 constpending=this.pendingPulls.shift();
 pending.resolve();
 return;
@@ -353,13 +357,15 @@ class Blob{
 pending.reject(error);
 return;
 }
-if(buffer!==undefined){
+// ReadableByteStreamController.enqueue errors if we submit a 0-length
+// buffer. We need to check for that here.
+if(buffer!==undefined&&buffer.byteLength!==0){
 c.enqueue(newUint8Array(buffer));
 }
 // We keep reading until we either reach EOS, some error, or we
 // hit the flow rate of the stream (c.desiredSize).
 queueMicrotask(()=>{
-if(c.desiredSize<=0){
+if(c.desiredSize<0){
 // A manual backpressure check.
 if(this.pendingPulls.length!==0){
 // A case of waiting pull finished (= not yet canceled)

test/parallel/test-blob.js

@@ -331,12 +331,54 @@ assert.throws(() => new Blob({}),{
 constb=newBlob(Array(10).fill('hello'));
 conststream=b.stream();
 constreader=stream.getReader();
-assert.strictEqual(stream[kState].controller.desiredSize,1);
+assert.strictEqual(stream[kState].controller.desiredSize,0);
 const{ value, done }=awaitreader.read();
 assert.strictEqual(value.byteLength,5);
 assert(!done);
 setTimeout(()=>{
-assert.strictEqual(stream[kState].controller.desiredSize,0);
+// The blob stream is now a byte stream hence after the first read,
+// it should pull in the next 'hello' which is 5 bytes hence -5.
+assert.strictEqual(stream[kState].controller.desiredSize,-5);
+},0);
+})().then(common.mustCall());
+
+(async()=>{
+constblob=newBlob(['hello','world']);
+conststream=blob.stream();
+constreader=stream.getReader({mode: 'byob'});
+constdecoder=newTextDecoder();
+constchunks=[];
+while(true){
+const{ value, done }=awaitreader.read(newUint8Array(100));
+if(done)break;
+chunks.push(decoder.decode(value,{stream: true}));
+}
+assert.strictEqual(chunks.join(''),'helloworld');
+})().then(common.mustCall());
+
+(async()=>{
+constb=newBlob(Array(10).fill('hello'));
+conststream=b.stream();
+constreader=stream.getReader({mode: 'byob'});
+assert.strictEqual(stream[kState].controller.desiredSize,0);
+const{ value, done }=awaitreader.read(newUint8Array(100));
+assert.strictEqual(value.byteLength,5);
+assert(!done);
+setTimeout(()=>{
+assert.strictEqual(stream[kState].controller.desiredSize,-5);
+},0);
+})().then(common.mustCall());
+
+(async()=>{
+constb=newBlob(Array(10).fill('hello'));
+conststream=b.stream();
+constreader=stream.getReader({mode: 'byob'});
+assert.strictEqual(stream[kState].controller.desiredSize,0);
+const{ value, done }=awaitreader.read(newUint8Array(2));
+assert.strictEqual(value.byteLength,2);
+assert(!done);
+setTimeout(()=>{
+assert.strictEqual(stream[kState].controller.desiredSize,-3);
 },0);
 })().then(common.mustCall());
 

test/wpt/status/FileAPI/blob.json

@@ -44,12 +44,5 @@
  },
 "Blob-slice.any.js":{
 "skip": "Depends on File API"
- },
-"Blob-stream.any.js":{
-"fail":{
-"expected": [
-"Reading Blob.stream() with BYOB reader"
- ]
- }
  }
 }