Expressions: Use enumerations rather than strings (#83741)

pkg/expr/classic/classic.go

@@ -54,7 +54,7 @@ type condition struct {
 	// Operator is the logical operator to use when there are two conditions in ConditionsCmd.
 	// If there are more than two conditions in ConditionsCmd then operator is used to compare
 	// the outcome of this condition with that of the condition before it.
-	Operator string
+	Operator ConditionOperatorType
 }
 
 // NeedsVars returns the variable names (refIds) that are dependencies
@@ -216,7 +216,7 @@ func (cmd *ConditionsCmd) executeCond(_ context.Context, _ time.Time, cond condi
 	return isCondFiring, isCondNoData, matches, nil
 }
 
-func compareWithOperator(b1, b2 bool, operator string) bool {
+func compareWithOperator(b1, b2 bool, operator ConditionOperatorType) bool {
 	if operator == "or" {
 		return b1 || b2
 	} else {
@@ -262,8 +262,17 @@ type ConditionEvalJSON struct {
 	Type   string    `json:"type"` // e.g. "gt"
 }
 
+// The reducer function
+// +enum
+type ConditionOperatorType string
+
+const (
+	ConditionOperatorAnd ConditionOperatorType = "and"
+	ConditionOperatorOr  ConditionOperatorType = "or"
+)
+
 type ConditionOperatorJSON struct {
-	Type string `json:"type"`
+	Type ConditionOperatorType `json:"type"`
 }
 
 type ConditionQueryJSON struct {

pkg/expr/commands.go

@@ -205,14 +205,14 @@ func (gr *ReduceCommand) Execute(ctx context.Context, _ time.Time, vars mathexp.
 type ResampleCommand struct {
 	Window        time.Duration
 	VarToResample string
-	Downsampler   string
+	Downsampler   mathexp.ReducerID
-	Upsampler     string
+	Upsampler     mathexp.Upsampler
 	TimeRange     TimeRange
 	refID         string
 }
 
 // NewResampleCommand creates a new ResampleCMD.
-func NewResampleCommand(refID, rawWindow, varToResample string, downsampler string, upsampler string, tr TimeRange) (*ResampleCommand, error) {
+func NewResampleCommand(refID, rawWindow, varToResample string, downsampler mathexp.ReducerID, upsampler mathexp.Upsampler, tr TimeRange) (*ResampleCommand, error) {
 	// TODO: validate reducer here, before execution
 	window, err := gtime.ParseDuration(rawWindow)
 	if err != nil {
@@ -271,7 +271,11 @@ func UnmarshalResampleCommand(rn *rawNode) (*ResampleCommand, error) {
 		return nil, fmt.Errorf("expected resample downsampler to be a string, got type %T", upsampler)
 	}
 
-	return NewResampleCommand(rn.RefID, window, varToResample, downsampler, upsampler, rn.TimeRange)
+	return NewResampleCommand(rn.RefID, window,
+		varToResample,
+		mathexp.ReducerID(downsampler),
+		mathexp.Upsampler(upsampler),
+		rn.TimeRange)
 }
 
 // NeedsVars returns the variable names (refIds) that are dependencies

pkg/expr/mathexp/resample.go

@@ -7,8 +7,23 @@ import (
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 )
 
+// The upsample function
+// +enum
+type Upsampler string
+
+const (
+	// Use the last seen value
+	UpsamplerPad Upsampler = "pad"
+
+	// backfill
+	UpsamplerBackfill Upsampler = "backfilling"
+
+	// Do not fill values (nill)
+	UpsamplerFillNA Upsampler = "fillna"
+)
+
 // Resample turns the Series into a Number based on the given reduction function
-func (s Series) Resample(refID string, interval time.Duration, downsampler string, upsampler string, from, to time.Time) (Series, error) {
+func (s Series) Resample(refID string, interval time.Duration, downsampler ReducerID, upsampler Upsampler, from, to time.Time) (Series, error) {
 	newSeriesLength := int(float64(to.Sub(from).Nanoseconds()) / float64(interval.Nanoseconds()))
 	if newSeriesLength <= 0 {
 		return s, fmt.Errorf("the series cannot be sampled further; the time range is shorter than the interval")
@@ -37,19 +52,19 @@ func (s Series) Resample(refID string, interval time.Duration, downsampler strin
 		var value *float64
 		if len(vals) == 0 { // upsampling
 			switch upsampler {
-			case "pad":
+			case UpsamplerPad:
 				if lastSeen != nil {
 					value = lastSeen
 				} else {
 					value = nil
 				}
-			case "backfilling":
+			case UpsamplerBackfill:
 				if sIdx == s.Len() { // no vals left
 					value = nil
 				} else {
 					_, value = s.GetPoint(sIdx)
 				}
-			case "fillna":
+			case UpsamplerFillNA:
 				value = nil
 			default:
 				return s, fmt.Errorf("upsampling %v not implemented", upsampler)
@@ -61,15 +76,15 @@ func (s Series) Resample(refID string, interval time.Duration, downsampler strin
 			ff := Float64Field(*fVec)
 			var tmp *float64
 			switch downsampler {
-			case "sum":
+			case ReducerSum:
 				tmp = Sum(&ff)
-			case "mean":
+			case ReducerMean:
 				tmp = Avg(&ff)
-			case "min":
+			case ReducerMin:
 				tmp = Min(&ff)
-			case "max":
+			case ReducerMax:
 				tmp = Max(&ff)
-			case "last":
+			case ReducerLast:
 				tmp = Last(&ff)
 			default:
 				return s, fmt.Errorf("downsampling %v not implemented", downsampler)

pkg/expr/mathexp/resample_test.go

@@ -13,8 +13,8 @@ func TestResampleSeries(t *testing.T) {
 	var tests = []struct {
 		name             string
 		interval         time.Duration
-		downsampler      string
+		downsampler      ReducerID
-		upsampler        string
+		upsampler        Upsampler
 		timeRange        backend.TimeRange
 		seriesToResample Series
 		series           Series

pkg/expr/models.go

@@ -54,10 +54,10 @@ type ResampleQuery struct {
 	Window string `json:"window" jsonschema:"minLength=1,example=1w,example=10m"`
 
 	// The downsample function
-	Downsampler string `json:"downsampler"`
+	Downsampler mathexp.ReducerID `json:"downsampler"`
 
 	// The upsample function
-	Upsampler string `json:"upsampler"`
+	Upsampler mathexp.Upsampler `json:"upsampler"`
 }
 
 type ThresholdQuery struct {

pkg/expr/reader.go

@@ -156,7 +156,7 @@ func (h *ExpressionQueryReader) ReadQuery(
 }
 
 func getReferenceVar(exp string, refId string) (string, error) {
-	exp = strings.TrimPrefix(exp, "%")
+	exp = strings.TrimPrefix(exp, "$")
 	if exp == "" {
 		return "", fmt.Errorf("no variable specified to reference for refId %v", refId)
 	}

pkg/expr/threshold.go

@@ -18,23 +18,31 @@ import (
 type ThresholdCommand struct {
 	ReferenceVar  string
 	RefID         string
-	ThresholdFunc string
+	ThresholdFunc ThresholdType
 	Conditions    []float64
 	Invert        bool
 }
 
+// +enum
+type ThresholdType string
+
 const (
-	ThresholdIsAbove        = "gt"
+	ThresholdIsAbove        ThresholdType = "gt"
-	ThresholdIsBelow        = "lt"
+	ThresholdIsBelow        ThresholdType = "lt"
-	ThresholdIsWithinRange  = "within_range"
+	ThresholdIsWithinRange  ThresholdType = "within_range"
-	ThresholdIsOutsideRange = "outside_range"
+	ThresholdIsOutsideRange ThresholdType = "outside_range"
 )
 
 var (
-	supportedThresholdFuncs = []string{ThresholdIsAbove, ThresholdIsBelow, ThresholdIsWithinRange, ThresholdIsOutsideRange}
+	supportedThresholdFuncs = []string{
+		string(ThresholdIsAbove),
+		string(ThresholdIsBelow),
+		string(ThresholdIsWithinRange),
+		string(ThresholdIsOutsideRange),
+	}
 )
 
-func NewThresholdCommand(refID, referenceVar, thresholdFunc string, conditions []float64) (*ThresholdCommand, error) {
+func NewThresholdCommand(refID, referenceVar string, thresholdFunc ThresholdType, conditions []float64) (*ThresholdCommand, error) {
 	switch thresholdFunc {
 	case ThresholdIsOutsideRange, ThresholdIsWithinRange:
 		if len(conditions) < 2 {
@@ -58,7 +66,7 @@ func NewThresholdCommand(refID, referenceVar, thresholdFunc string, conditions [
 
 type ConditionEvalJSON struct {
 	Params []float64     `json:"params"`
-	Type   string    `json:"type"` // e.g. "gt"
+	Type   ThresholdType `json:"type"` // e.g. "gt"
 }
 
 // UnmarshalResampleCommand creates a ResampleCMD from Grafana's frontend query.
@@ -121,7 +129,7 @@ func (tc *ThresholdCommand) Execute(ctx context.Context, now time.Time, vars mat
 }
 
 // createMathExpression converts all the info we have about a "threshold" expression in to a Math expression
-func createMathExpression(referenceVar string, thresholdFunc string, args []float64, invert bool) (string, error) {
+func createMathExpression(referenceVar string, thresholdFunc ThresholdType, args []float64, invert bool) (string, error) {
 	var exp string
 	switch thresholdFunc {
 	case ThresholdIsAbove:

pkg/expr/threshold_test.go

@@ -14,7 +14,7 @@ import (
 
 func TestNewThresholdCommand(t *testing.T) {
 	type testCase struct {
-		fn            string
+		fn            ThresholdType
 		args          []float64
 		shouldError   bool
 		expectedError string
@@ -107,7 +107,7 @@ func TestUnmarshalThresholdCommand(t *testing.T) {
 				require.IsType(t, &ThresholdCommand{}, command)
 				cmd := command.(*ThresholdCommand)
 				require.Equal(t, []string{"A"}, cmd.NeedsVars())
-				require.Equal(t, "gt", cmd.ThresholdFunc)
+				require.Equal(t, ThresholdIsAbove, cmd.ThresholdFunc)
 				require.Equal(t, []float64{20.0, 80.0}, cmd.Conditions)
 			},
 		},
@@ -172,10 +172,10 @@ func TestUnmarshalThresholdCommand(t *testing.T) {
 				cmd := c.(*HysteresisCommand)
 				require.Equal(t, []string{"B"}, cmd.NeedsVars())
 				require.Equal(t, []string{"B"}, cmd.LoadingThresholdFunc.NeedsVars())
-				require.Equal(t, "gt", cmd.LoadingThresholdFunc.ThresholdFunc)
+				require.Equal(t, ThresholdIsAbove, cmd.LoadingThresholdFunc.ThresholdFunc)
 				require.Equal(t, []float64{100.0}, cmd.LoadingThresholdFunc.Conditions)
 				require.Equal(t, []string{"B"}, cmd.UnloadingThresholdFunc.NeedsVars())
-				require.Equal(t, "lt", cmd.UnloadingThresholdFunc.ThresholdFunc)
+				require.Equal(t, ThresholdIsBelow, cmd.UnloadingThresholdFunc.ThresholdFunc)
 				require.Equal(t, []float64{31.0}, cmd.UnloadingThresholdFunc.Conditions)
 				require.True(t, cmd.UnloadingThresholdFunc.Invert)
 				require.NotNil(t, cmd.LoadedDimensions)
@@ -233,7 +233,7 @@ func TestCreateMathExpression(t *testing.T) {
 		expected    string
 
 		ref      string
-		function string
+		function ThresholdType
 		params   []float64
 	}
 
@@ -297,7 +297,7 @@ func TestCreateMathExpression(t *testing.T) {
 
 func TestIsSupportedThresholdFunc(t *testing.T) {
 	type testCase struct {
-		function  string
+		function  ThresholdType
 		supported bool
 	}
 
@@ -325,8 +325,8 @@ func TestIsSupportedThresholdFunc(t *testing.T) {
 	}
 
 	for _, tc := range cases {
-		t.Run(tc.function, func(t *testing.T) {
+		t.Run(string(tc.function), func(t *testing.T) {
-			supported := IsSupportedThresholdFunc(tc.function)
+			supported := IsSupportedThresholdFunc(string(tc.function))
 			require.Equal(t, supported, tc.supported)
 		})
 	}

pkg/services/ngalert/backtesting/eval_data.go

@@ -16,8 +16,8 @@ import (
 type dataEvaluator struct {
 	refID              string
 	data               []mathexp.Series
-	downsampleFunction string
+	downsampleFunction mathexp.ReducerID
-	upsampleFunction   string
+	upsampleFunction   mathexp.Upsampler
 }
 
 func newDataEvaluator(refID string, frame *data.Frame) (*dataEvaluator, error) {