fix: stream return EOF when openai return error (#184)

* fix: stream return EOF when openai return error

* perf: add error accumulator

* fix: golangci-lint

* fix: unmarshal error possibly null

* fix: error accumulator

* test: error accumulator use interface and add test code

* test: error accumulator add test code

* refactor: use stream reader to re-use stream code

* refactor: stream reader use generics

error_accumulator_test.go

@@ -0,0 +1,90 @@
+package openai //nolint:testpackage // testing private field
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/sashabaranov/go-openai/internal/test"
+)
+
+var (
+	errTestUnmarshalerFailed           = errors.New("test unmarshaler failed")
+	errTestErrorAccumulatorWriteFailed = errors.New("test error accumulator failed")
+)
+
+type (
+	failingUnMarshaller struct{}
+	failingErrorBuffer  struct{}
+)
+
+func (b *failingErrorBuffer) Write(_ []byte) (n int, err error) {
+	return 0, errTestErrorAccumulatorWriteFailed
+}
+
+func (b *failingErrorBuffer) Len() int {
+	return 0
+}
+
+func (b *failingErrorBuffer) Bytes() []byte {
+	return []byte{}
+}
+
+func (*failingUnMarshaller) unmarshal(_ []byte, _ any) error {
+	return errTestUnmarshalerFailed
+}
+
+func TestErrorAccumulatorReturnsUnmarshalerErrors(t *testing.T) {
+	accumulator := &errorAccumulate{
+		buffer:      &bytes.Buffer{},
+		unmarshaler: &failingUnMarshaller{},
+	}
+
+	err := accumulator.write([]byte("{"))
+	if err != nil {
+		t.Fatalf("%+v", err)
+	}
+	_, err = accumulator.unmarshalError()
+	if !errors.Is(err, errTestUnmarshalerFailed) {
+		t.Fatalf("Did not return error when unmarshaler failed: %v", err)
+	}
+}
+
+func TestErrorByteWriteErrors(t *testing.T) {
+	accumulator := &errorAccumulate{
+		buffer:      &failingErrorBuffer{},
+		unmarshaler: &jsonUnmarshaler{},
+	}
+	err := accumulator.write([]byte("{"))
+	if !errors.Is(err, errTestErrorAccumulatorWriteFailed) {
+		t.Fatalf("Did not return error when write failed: %v", err)
+	}
+}
+
+func TestErrorAccumulatorWriteErrors(t *testing.T) {
+	var err error
+	ts := test.NewTestServer().OpenAITestServer()
+	ts.Start()
+	defer ts.Close()
+
+	config := DefaultConfig(test.GetTestToken())
+	config.BaseURL = ts.URL + "/v1"
+	client := NewClientWithConfig(config)
+
+	ctx := context.Background()
+
+	stream, err := client.CreateChatCompletionStream(ctx, ChatCompletionRequest{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	stream.errAccumulator = &errorAccumulate{
+		buffer:      &failingErrorBuffer{},
+		unmarshaler: &jsonUnmarshaler{},
+	}
+
+	_, err = stream.Recv()
+	if !errors.Is(err, errTestErrorAccumulatorWriteFailed) {
+		t.Fatalf("Did not return error when write failed: %v", err)
+	}
+}