unit-tests for zero-rows-returned situations (#119)

* unit-tests for zero-rows-returned situations

* added more formats

Author: gabor

dataframe_test.go

@@ -0,0 +1,190 @@
+package sqlds_test
+
+import (
+	"context"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/data/sqlutil"
+	"github.com/grafana/sqlds/v3"
+	"github.com/grafana/sqlds/v3/test"
+	"github.com/stretchr/testify/require"
+)
+
+// we test how no-rows sql responses are converted to dataframes
+func TestNoRowsFrame(t *testing.T) {
+
+	tts := []struct {
+		name               string
+		data               test.Data
+		format             sqlutil.FormatQueryOption
+		expectedFieldCount int
+	}{
+		{
+			name:   "empty table",
+			format: sqlutil.FormatOptionTable,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "name",
+						DataType: "TEXT",
+						Kind:     "",
+					},
+					{
+						Name:     "age",
+						DataType: "INTEGER",
+						Kind:     int64(0),
+					},
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+		{
+			name:   "empty wide",
+			format: sqlutil.FormatOptionTimeSeries,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "time",
+						DataType: "TIMESTAMP",
+						Kind:     time.Unix(0, 0),
+					},
+					{
+						Name:     "v1",
+						DataType: "FLOAT",
+						Kind:     float64(0),
+					},
+					{
+						Name:     "v2",
+						DataType: "FLOAT",
+						Kind:     float64(0),
+					},
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+		{
+			name:   "empty long",
+			format: sqlutil.FormatOptionTimeSeries,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "time",
+						DataType: "TIMESTAMP",
+						Kind:     time.Unix(0, 0),
+					},
+					{
+						Name:     "tag",
+						DataType: "TEXT",
+						Kind:     "",
+					},
+					{
+						Name:     "value",
+						DataType: "FLOAT",
+						Kind:     float64(0),
+					},
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+		{
+			name:   "empty multi",
+			format: sqlutil.FormatOptionMulti,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "time",
+						DataType: "TIMESTAMP",
+						Kind:     time.Unix(0, 0),
+					},
+					{
+						Name:     "tag",
+						DataType: "TEXT",
+						Kind:     "",
+					},
+					{
+						Name:     "value",
+						DataType: "FLOAT",
+						Kind:     float64(0),
+					},
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+		{
+			name:   "logs",
+			format: sqlutil.FormatOptionLogs,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "time",
+						DataType: "TIMESTAMP",
+						Kind:     time.Unix(0, 0),
+					},
+					{
+						Name:     "text",
+						DataType: "TEXT",
+						Kind:     "",
+					},
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+		{
+			name:   "trace",
+			format: sqlutil.FormatOptionLogs,
+			data: test.Data{
+				Cols: []test.Column{
+					{
+						Name:     "time",
+						DataType: "TIMESTAMP",
+						Kind:     time.Unix(0, 0),
+					},
+					// FIXME: i do not know what kind of data is in trace-frames
+				},
+				Rows: [][]any{},
+			},
+			expectedFieldCount: 0,
+		},
+	}
+
+	for _, tt := range tts {
+		t.Run(tt.name, func(t *testing.T) {
+			id := "empty-frames" + tt.name
+			driver, _ := test.NewDriver(id, tt.data, nil, test.DriverOpts{})
+			ds := sqlds.NewDatasource(driver)
+
+			settings := backend.DataSourceInstanceSettings{UID: id, JSONData: []byte("{}")}
+			_, err := ds.NewDatasource(context.Background(), settings)
+
+			require.NoError(t, err)
+
+			req := backend.QueryDataRequest{
+				PluginContext: backend.PluginContext{
+					DataSourceInstanceSettings: &settings,
+				},
+				Queries: []backend.DataQuery{
+					{
+						RefID: "A",
+						JSON:  []byte(fmt.Sprintf(`{ "rawSql": "SELECT 42", "format": %d }`, tt.format)),
+					},
+				},
+			}
+
+			r, err := ds.QueryData(context.Background(), &req)
+			require.NoError(t, err)
+			d := r.Responses["A"]
+			require.NotNil(t, d)
+			require.Len(t, d.Frames, 1)
+			require.Len(t, d.Frames[0].Fields, tt.expectedFieldCount)
+
+		})
+	}
+}