fix: fix early cancel when RequestTimeout is provided for streaming requests (#3904)

Author: stainless-app[bot]

internal/requestconfig/requestconfig.go

@@ -295,6 +295,41 @@ func parseRetryAfterHeader(resp *http.Response) (time.Duration, bool) {
 	return 0, false
 }
 
+// isBeforeContextDeadline reports whether the non-zero Time t is
+// before ctx's deadline. If ctx does not have a deadline, it
+// always reports true (the deadline is considered infinite).
+func isBeforeContextDeadline(t time.Time, ctx context.Context) bool {
+	d, ok := ctx.Deadline()
+	if !ok {
+		return true
+	}
+	return t.Before(d)
+}
+
+// bodyWithTimeout is an io.ReadCloser which can observe a context's cancel func
+// to handle timeouts etc. It wraps an existing io.ReadCloser.
+type bodyWithTimeout struct {
+	stop func() // stops the time.Timer waiting to cancel the request
+	rc   io.ReadCloser
+}
+
+func (b *bodyWithTimeout) Read(p []byte) (n int, err error) {
+	n, err = b.rc.Read(p)
+	if err == nil {
+		return n, nil
+	}
+	if err == io.EOF {
+		return n, err
+	}
+	return n, err
+}
+
+func (b *bodyWithTimeout) Close() error {
+	err := b.rc.Close()
+	b.stop()
+	return err
+}
+
 func retryDelay(res *http.Response, retryCount int) time.Duration {
 	// If the API asks us to wait a certain amount of time (and it's a reasonable amount),
 	// just do what it says.
@@ -356,12 +391,17 @@ func (cfg *RequestConfig) Execute() (err error) {
 	shouldSendRetryCount := cfg.Request.Header.Get("X-Stainless-Retry-Count") == "0"
 
 	var res *http.Response
+	var cancel context.CancelFunc
 	for retryCount := 0; retryCount <= cfg.MaxRetries; retryCount += 1 {
 		ctx := cfg.Request.Context()
-		if cfg.RequestTimeout != time.Duration(0) {
-			var cancel context.CancelFunc
+		if cfg.RequestTimeout != time.Duration(0) && isBeforeContextDeadline(time.Now().Add(cfg.RequestTimeout), ctx) {
 			ctx, cancel = context.WithTimeout(ctx, cfg.RequestTimeout)
-			defer cancel()
+			defer func() {
+				// The cancel function is nil if it was handed off to be handled in a different scope.
+				if cancel != nil {
+					cancel()
+				}
+			}()
 		}
 
 		req := cfg.Request.Clone(ctx)
@@ -429,10 +469,15 @@ func (cfg *RequestConfig) Execute() (err error) {
 		return &aerr
 	}
 
-	if cfg.ResponseBodyInto == nil {
-		return nil
-	}
-	if _, ok := cfg.ResponseBodyInto.(**http.Response); ok {
+	_, intoCustomResponseBody := cfg.ResponseBodyInto.(**http.Response)
+	if cfg.ResponseBodyInto == nil || intoCustomResponseBody {
+		// We aren't reading the response body in this scope, but whoever is will need the
+		// cancel func from the context to observe request timeouts.
+		// Put the cancel function in the response body so it can be handled elsewhere.
+		if cancel != nil {
+			res.Body = &bodyWithTimeout{rc: res.Body, stop: cancel}
+			cancel = nil
+		}
 		return nil
 	}