add tests

README.md

@@ -264,6 +264,10 @@ variables:
 }
 ```
 
+### Caching layer
+
+DSL helpers that given the same input have deterministic output and are I/O intensive, should set the `Cacheable` property to `true`. This avoids to invoke the function multiple times and return always the same result.
+
 ### Thanks
 
 Knetic/govaluate - For providing a powerful expression evaluation package.

dsl_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/Knetic/govaluate"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/exp/maps"
 )
 
 func TestIndex(t *testing.T) {
@@ -469,8 +470,36 @@ func TestRandIntDslExpressions(t *testing.T) {
 	}
 }
 
-func evaluateExpression(t *testing.T, dslExpression string) interface{} {
-	compiledExpression, err := govaluate.NewEvaluableExpressionWithFunctions(dslExpression, DefaultHelperFunctions)
+func TestCachingLayer(t *testing.T) {
+	var (
+		callCount      int
+		expectedResult = "static value"
+		cacheableFunc  = dslFunction{
+			IsCacheable:  true,
+			Name:         "cacheable_func",
+			NumberOfArgs: 0,
+			Signatures:   nil,
+			ExpressionFunction: func(args ...interface{}) (interface{}, error) {
+				time.Sleep(time.Second)
+				callCount++
+				return expectedResult, nil
+			},
+		}
+	)
+
+	for i := 0; i < 100; i++ {
+		result := evaluateExpression(t, "cacheable_func()", cacheableFunc)
+		require.Equal(t, expectedResult, result)
+	}
+	require.Equal(t, 1, callCount)
+}
+
+func evaluateExpression(t *testing.T, dslExpression string, functions ...dslFunction) interface{} {
+	helperFunctions := maps.Clone(DefaultHelperFunctions)
+	for _, function := range functions {
+		helperFunctions[function.Name] = function.Exec
+	}
+	compiledExpression, err := govaluate.NewEvaluableExpressionWithFunctions(dslExpression, helperFunctions)
 	require.NoError(t, err, "Error while compiling the %q expression", dslExpression)
 
 	actualResult, err := compiledExpression.Evaluate(make(map[string]interface{}))

engine.go

@@ -70,7 +70,7 @@ func Regex(regxp string) (*regexp.Regexp, error) {
 	if err != nil {
 		return nil, err
 	}
-	RegexStore.Set(regxp, compiled)
+	_ = RegexStore.Set(regxp, compiled)
 
 	return compiled, nil
 }

func.go

@@ -62,7 +62,7 @@ func (d dslFunction) Exec(args ...interface{}) (interface{}, error) {
 	result, err := d.ExpressionFunction(args...)
 
 	if d.IsCacheable {
-		resultCache.Set(functionHash, result)
+		_ = resultCache.Set(functionHash, result)
 	}
 
 	return result, err

go.mod

@@ -17,6 +17,7 @@ require (
 	github.com/sashabaranov/go-openai v1.14.1
 	github.com/spaolacci/murmur3 v1.1.0
 	github.com/stretchr/testify v1.8.4
+	golang.org/x/exp v0.0.0-20230315142452-642cacee5cc0
 )
 
 require (
@@ -41,7 +42,6 @@ require (
 	github.com/ulikunitz/xz v0.5.11 // indirect
 	github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/exp v0.0.0-20230315142452-642cacee5cc0 // indirect
 	golang.org/x/mod v0.9.0 // indirect
 	golang.org/x/net v0.12.0 // indirect
 	golang.org/x/sys v0.10.0 // indirect