fix: templating: allow templating to render empty string as result

Signed-off-by: Romain Beuque <romain.beuque@corp.ovh.com>

engine/engine_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/loopfz/gadgeto/zesty"
 	"github.com/ovh/configstore"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/ovh/utask"
 	"github.com/ovh/utask/db"
@@ -625,6 +626,26 @@ func TestBaseOutput(t *testing.T) {
 	assert.Equal(t, "bar", output["foo"])
 }
 
+func TestEmptyStringInput(t *testing.T) {
+	input := map[string]interface{}{
+		"quantity": -2.3,
+		"foo":      "",
+	}
+	res, err := createResolution("input.yaml", input, nil)
+	assert.NotNil(t, res)
+	assert.Nil(t, err)
+
+	res, err = runResolution(res)
+
+	require.Nilf(t, err, "got error %s", err)
+	require.NotNil(t, res)
+	assert.Equal(t, resolution.StateDone, res.State)
+	assert.Equal(t, step.StateDone, res.Steps["stepOne"].State)
+
+	output := res.Steps["stepOne"].Output.(map[string]interface{})
+	assert.Equal(t, "", output["foo"])
+}
+
 func TestScriptPlugin(t *testing.T) {
 	argv := "world"
 	res, err := createResolution("execScript.yaml", map[string]interface{}{"argv": argv}, nil)

engine/step/apply.go

@@ -3,11 +3,16 @@ package step
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"reflect"
 
 	"github.com/ovh/utask/engine/values"
 )
 
+var (
+	errNotTemplatable = errors.New("value given is not templatable")
+)
+
 func resolveObject(val *values.Values, objson json.RawMessage, item interface{}, stepName string) ([]byte, error) {
 	obj, err := rawResolveObject(val, objson, item, stepName)
 	if err != nil {
@@ -61,12 +66,14 @@ func applyMap(val *values.Values, v reflect.Value, item interface{}, stepName st
 			applySlice(val, mv, item, stepName)
 		case reflect.String:
 			newValue, err := applyString(val, mv, item, stepName)
-			if err != nil {
-				return err
-			}
-
-			if newValue != "" {
+			switch err {
+			case nil:
 				v.SetMapIndex(iter.Key(), reflect.ValueOf(newValue))
+			case errNotTemplatable:
+				// current value Kind is string, but actual type could not be string (e.g. json.Number)
+				// in that case, we should keep the actual value as it will never be templated
+			default:
+				return err
 			}
 		}
 	}
@@ -90,12 +97,14 @@ func applySlice(val *values.Values, v reflect.Value, item interface{}, stepName
 			applySlice(val, elem, item, stepName)
 		case reflect.String:
 			newValue, err := applyString(val, elem, item, stepName)
-			if err != nil {
-				return err
-			}
-
-			if newValue != "" {
+			switch err {
+			case nil:
 				mv.Set(reflect.ValueOf(newValue))
+			case errNotTemplatable:
+				// current value Kind is string, but actual type could not be string (e.g. json.Number)
+				// in that case, we should keep the actual value as it will never be templated
+			default:
+				return err
 			}
 		}
 	}
@@ -107,7 +116,7 @@ func applyString(val *values.Values, v reflect.Value, item interface{}, stepName
 	strval := v.Interface()
 	str, ok := strval.(string)
 	if !ok {
-		return "", nil
+		return "", errNotTemplatable
 	}
 	resolved, err := val.Apply(str, item, stepName)
 	if err != nil {

engine/templates_tests/input.yaml

@@ -8,11 +8,16 @@ inputs:
       collection: false
       type: number
       optional: false
+    - name: foo
+      description: A string value
+      type: string
+      optional: true
+      default: ""
 steps:
     stepOne:
         description: first step
         idempotent: true
         retry_pattern: seconds
         action:
             type: echo
-            configuration: {output: {value: "{{.input.quantity}}"}}
+            configuration: {output: {value: "{{.input.quantity}}", foo: "{{.input.foo}}"}}