[OpenAI] Fix streaming (Azure#28351)

### Packages impacted by this PR
@azure/openai

### Issues associated with this PR
Azure#28342

### Describe the problem that is addressed by this PR
In `TransformStream`, the transform function shouldn't call
`controller.terminate()` unless it is expected that an error will be
thrown in the code that is consuming the writable stream. This PR
removes that call. Thanks @xirzec for the investigation!

UPDATE: Since the transformer stream is no longer ending, the idea of a
disposition operation is irrelevant. This is because the underlying
readable stream remains perpetually linked to the transformer stream,
making it impossible to cancel a stream that's locked. Now that I think
about it, the concept of disposition seems unnecessary in this case to
begin with. Once you're finished with the stream, there's no real need
for disposal so I deleted it. If a user wishes to cancel the stream,
they should use the standard method of calling the cancel API.

### What are the possible designs available to address the problem? If
there are more than one possible design, why was the one in this PR
chosen?
N/A

### Are there test cases added in this PR? _(If not, why?)_
We don't test on Bun but we have plenty chat completions tests.

### Provide a list of related PRs _(if any)_
N/A

### Command used to generate this PR:**_(Applicable only to SDK release
request PRs)_

### Checklists
- [x] Added impacted package name to the issue description
- [ ] Does this PR needs any fixes in the SDK Generator?** _(If so,
create an Issue in the
[Autorest/typescript](https://github.com/Azure/autorest.typescript)
repository and link it here)_
- [x] Added a changelog (if necessary)

sdk/openai/openai/CHANGELOG.md

@@ -10,6 +10,7 @@
 
 - Fix a bug where `toolChoice` field in the input options to chat completion methods wasn't defined correctly.
 - Fix a bug where the service returns undefined `choices` in chat completion methods.
+- Fix a bug in chat completion methods where the returned stream was causing an error in Bun.
 
 ### Other Changes
 

sdk/openai/openai/review/openai.api.md

@@ -502,7 +502,7 @@ export interface EmbeddingsUsage {
 }
 
 // @public
-export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T>, AsyncDisposable {
+export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T> {
 }
 
 // @public

sdk/openai/openai/sources/customizations/api/oaiSse.ts

@@ -17,8 +17,7 @@ export async function getOaiSSEs<TEvent, O extends Record<string, any>>(
   const jsonParser = new TransformStream<EventMessage, TEvent>({
     transform: async (chunk, controller) => {
       if (chunk.data === "[DONE]") {
-        controller.terminate();
-        return eventStream[Symbol.asyncDispose]();
+        return;
       }
       controller.enqueue(
         toEvent(
@@ -31,5 +30,5 @@ export async function getOaiSSEs<TEvent, O extends Record<string, any>>(
     },
   });
   /** TODO: remove these polyfills once all supported runtimes support them */
-  return polyfillStream(eventStream.pipeThrough(jsonParser), () => eventStream.cancel());
+  return polyfillStream(eventStream.pipeThrough(jsonParser));
 }

sdk/openai/openai/sources/customizations/api/readableStreamUtils.ts

@@ -1,25 +1,11 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 
-export function polyfillStream<T>(
-  stream: ReadableStream<T>,
-  dispose: () => PromiseLike<void>,
-): ReadableStream<T> & AsyncIterable<T> & AsyncDisposable {
+export function polyfillStream<T>(stream: ReadableStream<T>): ReadableStream<T> & AsyncIterable<T> {
   makeAsyncIterable<T>(stream);
-  makeAsyncDisposable(stream, dispose);
   return stream;
 }
 
-function makeAsyncDisposable<T>(
-  webStream: any,
-  dispose: () => PromiseLike<void>,
-): asserts webStream is ReadableStream<T> & AsyncDisposable {
-  (Symbol.asyncDispose as any) ??= Symbol("Symbol.asyncDispose");
-  if (!webStream[Symbol.asyncDispose]) {
-    webStream[Symbol.asyncDispose] = () => dispose();
-  }
-}
-
 function makeAsyncIterable<T>(
   webStream: any,
 ): asserts webStream is ReadableStream<T> & AsyncIterable<T> {

sdk/openai/openai/sources/customizations/models/models.ts

@@ -870,4 +870,4 @@ export interface ChatMessageImageUrl {
 }
 
 /** A readable stream that is iterable and disposable. */
-export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T>, AsyncDisposable {}
+export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T> {}

sdk/openai/openai/src/api/oaiSse.ts

@@ -25,8 +25,7 @@ export async function getOaiSSEs<TEvent, O extends Record<string, any>>(
   const jsonParser = new TransformStream<EventMessage, TEvent>({
     transform: async (chunk, controller) => {
       if (chunk.data === "[DONE]") {
-        controller.terminate();
-        return eventStream[Symbol.asyncDispose]();
+        return;
       }
       controller.enqueue(
         toEvent(
@@ -39,5 +38,5 @@ export async function getOaiSSEs<TEvent, O extends Record<string, any>>(
     },
   });
   /** TODO: remove these polyfills once all supported runtimes support them */
-  return polyfillStream(eventStream.pipeThrough(jsonParser), () => eventStream.cancel());
+  return polyfillStream(eventStream.pipeThrough(jsonParser));
 }

sdk/openai/openai/src/api/readableStreamUtils.ts

@@ -9,25 +9,11 @@
  * If you need to make changes, please do so in the original source file, \{project-root\}/sources/custom
  */
 
-export function polyfillStream<T>(
-  stream: ReadableStream<T>,
-  dispose: () => PromiseLike<void>,
-): ReadableStream<T> & AsyncIterable<T> & AsyncDisposable {
+export function polyfillStream<T>(stream: ReadableStream<T>): ReadableStream<T> & AsyncIterable<T> {
   makeAsyncIterable<T>(stream);
-  makeAsyncDisposable(stream, dispose);
   return stream;
 }
 
-function makeAsyncDisposable<T>(
-  webStream: any,
-  dispose: () => PromiseLike<void>,
-): asserts webStream is ReadableStream<T> & AsyncDisposable {
-  (Symbol.asyncDispose as any) ??= Symbol("Symbol.asyncDispose");
-  if (!webStream[Symbol.asyncDispose]) {
-    webStream[Symbol.asyncDispose] = () => dispose();
-  }
-}
-
 function makeAsyncIterable<T>(
   webStream: any,
 ): asserts webStream is ReadableStream<T> & AsyncIterable<T> {

sdk/openai/openai/src/models/models.ts

@@ -1566,4 +1566,4 @@ export type OnYourDataVectorizationSource =
   | OnYourDataModelIdVectorizationSource;
 
 /** A readable stream that is iterable and disposable. */
-export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T>, AsyncDisposable {}
+export interface EventStream<T> extends ReadableStream<T>, AsyncIterable<T> {}