fix: dynamic frame panic (#958)

fix: dynamic frame panic
---------

Co-authored-by: Andres Martinez Gotor <andres.martinez@grafana.com>
Co-authored-by: Zoltán Bedi <zoltan.bedi@gmail.com>

data/sqlutil/dynamic_frame.go

@@ -10,13 +10,18 @@ import (
 
 const STRING = "string"
 
-func isDynamic(converters []Converter) bool {
+// removeDynamicConverter filters out the dynamic converter.  It is not a valid converter.
+func removeDynamicConverter(converters []Converter) (bool, []Converter) {
+	var filtered []Converter
+	var isDynamic bool
 	for _, conv := range converters {
 		if conv.Dynamic {
-			return true
+			isDynamic = true
+		} else {
+			filtered = append(filtered, conv)
 		}
 	}
-	return false
+	return isDynamic, filtered
 }
 
 func findDataTypes(rows Rows, rowLimit int64, types []*sql.ColumnType) ([]Field, [][]interface{}, error) {

data/sqlutil/dynamic_frame_test.go

@@ -29,6 +29,7 @@ func TestDynamicFrame(t *testing.T) {
 		itr: mock,
 	}
 
+	_, converters = removeDynamicConverter(converters)
 	frame, err := frameDynamic(rows, 100, types, converters)
 	assert.Nil(t, err)
 	assert.NotNil(t, frame)
@@ -64,3 +65,42 @@ func (rs *MockRows) Scan(dest ...interface{}) error {
 	}
 	return nil
 }
+
+func TestDynamicFrameShouldNotPanic(t *testing.T) {
+	kind := &sql.ColumnType{}
+	types := []*sql.ColumnType{}
+	types = append(types, kind)
+	converters := []Converter{dynamic()}
+	data := [][]interface{}{}
+	mockRow := []interface{}{}
+	val := string("foo")
+	mockRow = append(mockRow, val)
+	data = append(data, mockRow)
+	mock := &MockRows{
+		data:  data,
+		index: -1,
+	}
+	rows := Rows{
+		itr: mock,
+	}
+
+	_, converters = removeDynamicConverter(converters)
+	frame, err := frameDynamic(rows, 100, types, converters)
+	assert.Nil(t, err)
+	assert.NotNil(t, frame)
+
+	assert.Equal(t, 1, frame.Rows())
+
+	actual := frame.Fields[0].At(0).(*string)
+	assert.Equal(t, val, *actual)
+}
+
+// dynamic is the converter that uses the results to determine data types
+func dynamic() Converter {
+	kind := "dynamic"
+	return Converter{
+		Name:          kind,
+		InputTypeName: kind,
+		Dynamic:       true,
+	}
+}

data/sqlutil/sql.go

@@ -25,7 +25,9 @@ func FrameFromRows(rows *sql.Rows, rowLimit int64, converters ...Converter) (*da
 		return nil, err
 	}
 
-	if isDynamic(converters) {
+	// If there is a dynamic converter, we need to use the dynamic framer
+	// and remove the dynamic converter from the list of converters ( it is not valid, just a flag )
+	if isDynamic, converters := removeDynamicConverter(converters); isDynamic {
 		rows := Rows{itr: rows}
 		return frameDynamic(rows, rowLimit, types, converters)
 	}